Unit 1 Flashcards
1
Q
List some functions that microbes carry out that are beneficial to humans.
A
- Decompose organic waste
- Generate oxygen by photosynthesis
- Produce chemical products such as vitamins, ethanol, and acetone
- Produce fermented foods such as vinegar, cheese, and bread
- Produce products used in manufacturing (cellulase) and disease treatment (insulin)
2
Q
What is binomial nomenclature?
A
System for naming organisms, each organism has two names, the genus and specific epithet, names are “Latinized”…may be descriptive or honor a scientist. (E. Coli)
3
Q
Carolus Linnaeus
A
Established the system of scientific nomenclature (binomial nomenclature)
4
Q
What are the main distinguishing characteristics for Bacteria?
A
Single-celled prokaryote, peptidoglycan cell walls, divide by binary fission, derive nutrition from organic and inorganic chemicals or photosynthesis.
5
Q
What are the main distinguishing characteristics for Archaea?
A
Prokaryote, peptidoglycan lacking walls, often live in extreme environments (Methanogens, extreme halophiles, extreme thermophiles)
6
Q
What are the main distinguishing characteristics for Fungi?
A
Eukaryotes, chitin cell walls, absorb organic chemicals for energy (yeasts are unicellular, molds and mushrooms are multicellular)
7
Q
What are the main distinguishing characteristics for Protozoa?
A
Eukaryotes, absorb and ingest organic chemicals, may be motile via pseudopods, cilia, or flagella, free-living or parasitic.
8
Q
What are the main distinguishing characteristics for Algae?
A
Eukaryotes, cellulose cell walls, found in freshwater, saltwater, and soil, use photosynthesis for energy, produce oxygen and carbohydrates.
9
Q
What are the main distinguishing characteristics for Viruses?
A
Acellular, consist of DNA and RNA core, core surrounded by protein coat, coat be enclosed in a lipid envelope, replicated only when living within a host cell, inert outside living host.
10
Q
What are the main distinguishing characteristics for Multicellular animal parasites?
A
Eukaryotes, multicellular animals, not strictly microorganisms, parasitic roundworms and flatworms are called helminths (some microscopic stages in their life cycles)
11
Q
Carl Woese
A
Developed a classification of microorganisms with three domains based on cellular organization (Bacteria, Archaea, Eukarya)
12
Q
Robert Hooke
A
First reported that living things are composed of “little boxes” or cells, marked the beginning of cell theory (All living things are composed of cells)
13
Q
Anton can Leeuwenhoek
A
Observed the first microbes “animalcules” through a magnifying lens
14
Q
Francisco Redi
A
Did the decaying meat experiment in jars, seemingly debunking spontaneous generation.
15
Q
John Needham
A
Boiled nutrient broth and placed it in covered flasks (microbial growth) seeming to support spontaneous generation.
16
Q
Lazzaro Spallanzani
A
Placed nutrient broth in sealed flask then heated (no microbial growth), seems to support biogenesis
17
Q
Rudolf Virchow
A
Said cells arise from preexisting cells
18
Q
Louis Pasteur
A
Demonstrated that microbes are present in the air with his experiment using S-shaped flasks. Disproved spontaneous generation. He also came up with pasteurization and showed that microbes are responsible for fermentation.
19
Q
Agostino Bassi
A
Showed that a silkworm disease was caused by a fungus
20
Q
Ignaz Semmelweiss
A
Advocated handwashing to prevent transmission of puerperal fever between obstetric patients
21
Q
Joseph Lister
A
Used a chemical antiseptic (phenol) to prevent infection in surgical wounds, proving that microbes cause surgical wound infection.
22
Q
Robert Koch
A
Developed a system of experimental steps called Koch;s Postulates to demonstrate a specific microbe causes a specific disease.
23
Q
Edward Jenner
A
Developed the first vaccine for smallpox (Inoculated someone with cowpox virus, making them immune to smallpox)
24
Q
Paul Ehrlich
A
Used the first synthetic chemotherapeutic agent
25
Alexander Fleming
Discovered the first antibiotic by accident (Penicillin)
26
Rebecca Lancefield
Classified streptococci based on their cell wall components (major advance in immunology)
27
Dmitri Iwanowski and Wendell Stanley
Discovered the cause of mosaic disease of tobacco as a virus.
28
Paul Berg
Inserted animal DNA into bacterial DNA, and the bacteria produced an animal protein.
29
George Beadle and Edward Tatum
Showed that genes encode a cell's enzymes
30
Oswald Avery, Colin MacLeod, and Maclyn McCarty
Proved that DNA is the hereditary material
31
James Watson and Francis Crick
Proposed a model of DNA structure
32
Francois Jacob and Jacques Monod
Discovered the role of mRNA in protein synthesis
33
Define and distinguish between spontaneous generation and biogenesis.
Spontaneous generation was the theory that life arises from nonliving matter, and biogenesis was theory that living cells arise only from preexisting living cells.
34
Chemotherapy
The treatment of disease with chemicals
35
Antibiotics
Chemicals produced by bacteria and fungi that nihibit or kill other microbes
36
Magic bullet
Can kill a microbe without harming the host (synthetic drugs)
37
Bacteriology
Study of bacteria
38
Mycology
Study of fungi
39
Parasitology
Study of protozoa and parasitic worms
40
Immunology
Study of immunity (vaccines and interferons are used to prevent and cure viral diseases)
41
Virology
Study of viruses (Electron microscopes have made it possible to study the structure of viruses in detail)
42
Microbial Genetics
Study of how microbes inherit traits
43
Molecular biology
Study of how DNA directs protein synthesis
44
Genomics
Study of an organism's genes; has provided new tools for classifying microorganisms.
45
Recombinant DNA
DNA made from two different sources
46
Microbial ecology
Study of the relationship between microorganisms and their environment
47
Biotechnology
The use of microbes for practical applications, such as producing foods and chemicals
48
Gene therapy
Replacement of missing or defective genes in human cells
49
Microbiota (normal)
Microbes present in or on the human body.
50
What is a biolfilm and why is it important?
When microbes attach to a solid surface and grow into masses, biofilms can cause infections and are often resistant to antibiotics.
51
What is an emerging infectious disease with examples?
New diseases and disease increasing in incidence (MRSA, AIDS, Ebola, Covid-19)
52
Units of Measurement conversions (m, mm, μm, nm)
1 μm = 10^-6 m = 10^-3 mm
1 nm = 10^-9 m = 10^-6 mm
1000 nm = 1 μm
0.001 μm = 1 nm
53
Define magnification and explain what is meant by total magnification.
Magnification is the ability of a lens to enlarge an image of an object, total magnification is the combined magnification of all lenses in a microscope (objective lense + ocular lense = total magnification)
54
What is resolution and how does wavelength of light affect resolution?
Resolution is the ability of the lenses to distinguish two points, shorter wavelengths of light provide greater resolution
55
What microscopes use light for imaging?
Compound light, darkfield, phase-contrast, differential interference contrast (DIC), fluorescence, and confocal
56
Ocular lens
Eyepiece, remagnifies the image formed by the objective lens.
57
Illuminator
Light source
58
Condenser lens
Focuses light through specimen
59
Body tube
Transmits the image from the objective lens to the ocular lens
60
Prism
Bends light towards ocular lens
61
What is the refractive index and why immersion oil is needed to overcome a high refraction index?
Refractive index is the light-bending ability of a medium, immersion oil is used to keep light from refracting
62
Distinguish between brightfield and darkfield microscopy.
In brightfield microscopy, dark objects are visible against a bright background, light reflected off the specimen does not enter the objective lens. In darkfield microscopy, light objects are visible against a dark background, opaque disc placed in condenser, and only light reflected off the specimen enters the objective lens.
63
How is light focused on a specimen in phase contrast and differential interference contrast microscopy?
Phase contrast brings together two sets of light rays, direct rays, and diffracted rays to form an image, and DIC uses two light beams and prisms to split light beams, giving more contrast and color to the specimen
64
How are specimens viewed when using fluorescence?
```
Uses UV (short wavelength) light
•Fluorescent substances absorb UV light and emit longer wavelength (visible) light
•Cells may be stained with fluorescent dyes (fluorochromes) if they do not naturally fluoresce
```
65
How are specimens viewed when using confocal?
* Cells are stained with fluorochrome dyes
* Short-wavelength (blue) light is used to excite a single plane of a specimen
* Each plane in a specimen is illuminated and a three-dimensional image is constructed with a computer
66
How are specimens viewed when using two-photon microscopy?
* Cells are stained with fluorochrome dyes
* Two photons of long-wavelength (red) light are used to excite the dyes
* Can study living cells up to 1 mm deep
67
What kind of dyes are used in fluorescence, confocal and two-photon microscopy?
Fluorescent dyes (fluorochromes)
68
Between fluorescence, confocal, and two-photon microscopy, which gives a 3-D image?
Confocal microscopy
69
What is used to image specimens in electron microscopy and how does this effect resolution and magnification?
Electron microscopy uses electrons instead of light, the shorter wavelength of electrons gives greater resolution, used for images too small to be seen with light microscopy (viruses) *Scanning and transmission electron microscopy
70
Distinguish between scanning and transmission electron microscopy.
In transmission electron microscopy, a beam of electrons passes through ultrathin sections of a specimen, then through an electromagnetic lens, then focused on a projector lens, specimens may be stained with heavy-metal salts for contrast, magnifies objects 10,000 to 100,000×; resolution of 10 pm and in Scanning electron microscopy, an electron gun produces a beam of electrons that scans the surface of an entire specimen, secondary electrons emitted from the specimen produce a three-dimensional image, magnifies objects 1000 to 10,000×; resolution of 10 nm
71
Distinguish between scanning tunneling and atomic force microscopy.
Scanning tunneling microscopy uses a tungsten probe to scan a specimen and reveal details of its surface, Resolution of 1/100 of an atom and atomic force microscopy uses a metal-and-diamond probe placed onto a specimen, produces 3-D images
72
Explain how specimens are prepared for staining.
A thin film of a material containing is microorganisms spread over a slide (smear), microorganisms are fixed(attached) to the slide, which kills the microorganisms
73
Distinguish between acidic dye and a basic dye
In a basic dye, the chromophore is a cation (+ charged ion), in an acidic dye, the chromophore is an anion (- charged ion).
74
Distinguish between direct (positive) staining and negative staining
Staining the background instead of the cell is a negative stain, staining the cells and leaving the background colorless is positive staining.
75
Distinguish between simple and differential staining.
Simple stains use a single dye and differential stains use multiple dyes to distinguish between bacteria (gram stain/ acid-fast stain)
76
Explain the steps of the gram stain technique.
Crystal violet is applied (stains cells purple), Iodine is applied (mordant/ cells still purple), alcohol wash (decolorization/ gram positive cells are purple/ negative cells are colorless), Safranin applied (counterstain/ gram negative cells turn pink or red)
77
Differentiate between gram positive and gram negative cells
Gram positive cells have thick peptidoglycan cell walls and stain purple, gram-negative cells have thin peptidoglycan cell walls and a layer of lipopolysaccharides and stain pink/red.
78
Why is acid-fast stain named as it is?
They are named this because during the acid fast staining procedure the cells retain the primary dye (carbol fuchsin) despite decolorization with acid-alcohol
79
Which bacteria can be identified with acid-fast staining?
Mycobacterium and Nocardia
80
In capsule staining what structure is stained and what dye is used?
Capsules are a gelatinous covering that do not accept most dyes, suspension of India ink or nigrosin contrasts the background with the capsule, which appears as a halo around the cell
81
In endospore staining, what structure is stained and what dye is used?
Endospores are resistant, dormant structures inside some cells that cannot be stained by ordinary methods
•Primary stain: malachite green, usually with heat
•Decolorize cells: water
•Counterstain: safranin
•Spores appear green within red or pink cells
82
In flagella staining, what structure is stained and what dye is used?
Flagella are structures of locomotion
| •Uses a mordant and carbolfuchsin
83
Identify and describe the three subatomic particles that comprise an atom.
Electrons: negatively charged particles
Protons: positively charged particles
Neutrons: uncharged particles
84
Element
Atoms with the same number of protons are classified as the same chemical element
85
Atomic number
Number of protons in the nucleus
86
Atomic weight
Total number of protons and neutrons in an atom
87
Isotope
Isotopes of an element are atoms with different numbers of neutrons
88
Molecule
A group of atoms bonded together
89
Compound
Contains two or more kind of atoms (H2O)
90
Molecular weight
The sum of the atomic weights in a molecule
91
Mole
One mole of a substance is its molecular weight in grams
92
Which chemical elements are most abundant in living organisms?
Hydrogen (H), carbon (C), nitrogen (N), oxygen (O)
93
What is the valence number of an atom and how does this number influence chemical bonds?
The number of missing or extra electrons in the outermost shell is known as the valence–How many bonds the atom typically forms
94
Distinguish between an ionic bond and covalent bond and give examples.
Ionic bonds are attractions between ions of opposite charge–One atom loses electrons, and another gains electrons (NA+Cl-=NaCl), Covalent bonds form when two atoms share one or more pairs of electrons (Carbon atoms and hydrogen atoms form methane molecule-Ch4)
95
What is a hydrogen bond?
Hydrogen bonds form when a hydrogen atom that is covalently bonded to an O or N atom is attracted to another N or O atom in another molecule
96
Distinguish between endergonic and exergonic reactions
Endergonic reactions absorb energy, and exergonic reactions release energy.
97
Distinguish between synthesis, decomposition, and exchange reactions.
synthesis reactions occur when atoms, ions, or molecules combine to form new, larger molecules (A+B=AB), Decomposition reactions occur when a molecule is split into smaller molecules, ions, or atoms (AB-->A+B), and Exchange reactions are part synthesis and part decomposition (NaOH+HCl --> NaCl+H2O)
98
Distinguish between anabolic and catabolic reactions
Catabolic reactions break down larger molecules into their constituent smaller parts, and anabolic reactions synthesize larger molecules from smaller constituent parts
99
Distinguish between reversible and irreversible reactions.
Irreversible chemical reactions can occur in only one direction. The reactants can change to the products, but the products cannot change back to the reactants. Reversible chemical reactions can occur in both directions. The reactants can change to the products, and the products can also change back to the reactants.
100
Acids
Substances that dissociate into one or more (protons) and one or more negative ions ( HCl -->H+ & Cl-)
101
Bases
Substances that dissociate into one or more (hydroxide) ions OH- (NaOH --> Na+ & OH-)
102
Salts
Substances that dissociate into cations and anions, neither of which is H+ or OH- (NaCl --> Na+ & Cl-)
103
Distinguish between organic and inorganic compounds
Organic compounds always contain carbon and hydrogen; typically structurally complex/ inorganic compounds typically lack carbon; usually small and structurally simple)
104
Why is the polarity of water important to its function?
The polarity of water is responsible for effectively dissolving other polar molecules, such as sugars and ionic compounds such as salt. Ionic compounds dissolve in water to form ions. This is important to remember because for most biological reactions to occur, the reactants must be dissolved in water.
105
Explain how dehydration synthesis and condensation reactions are important to macromolecules.
Macromolecules are polymers consisting of many small repeating molecules called monomers, monomers join by dehydration synthesis or condensation reactions (R-OH+OH-R' --> R-R' + H2O)
106
What is a carbohydrate and what is the general chemical formula for carbohydrates?
Serve as cell structures and cellular energy sources, include sugars and starches, consist of C, H, and O with the formuls (CH2O)n, many carbohydrates are isomers (Molecules with same chemical formula, but different structures)
107
Distinguish between a monosaccharide, disaccharide, and polysaccharide, give examples for each.
* Monosaccharides are simple sugars with three to seven carbon atoms–Glucose and deoxyribose are examples
* Disaccharidesare formed when two monosaccharides are joined in a dehydration synthesis–Disaccharides can be broken down by hydrolysis–Sucrose and maltose are examples
* Polysaccharides consist of tens or hundreds of monosaccharides joined through dehydration synthesis–Starch, glycogen, dextran, and cellulose are polymers of glucose that differ in their bonding and function
108
What is a lipid and what atoms are typically found in lipids?
Lipids are the primary components of cell membranes, consist of C,H, and O, nonpolar and insoluble in water.
109
What are the components of a fat or triglyceride?
Contain glycerol and fatty acids; formed by dehydration synthesis
110
Distinguish between saturated and unsaturated fat
Saturated fat has no double bonds in the fatty acids, and unsaturated fats have one or more double bonds in the fatty acids
111
Distinguish between Cis and trans fat
Cis- H atoms on the same side of the double bond.
| Trans- H atoms on the opposite side of the double bonds.
112
What is a phospholipid and why is it important?
Cell membranes are made of complex lipids ( Contain C, H, and O + P, N, and/or S) called phospholipids–Glycerol, two fatty acids, and a phosphate group, have polar and non polar regions *Important in allowing selective passage of molecules and ions into and out of the cell
113
What is a steroid and why is it important?
* Four carbon rings with an -OH group attached to one ring
| * Part of membranes that keep the membranes fluid
114
What is a protein?
Macromolecule consisting of one or more amino acid chains
115
What atoms are typically found in proteins?
C, H, O, N, and sometimes S
116
What are the functions of proteins?
•Essential in cell structure and function
–Enzymes that speed chemical reactions
–Transporter proteins that move chemicals across membranes
–Flagella that aid in movement
–Some bacterial toxins and cell structures
117
Describe the basic structure of an amino acid
•Amino acids contain an alpha-carbon that has an attached:
–Carboxyl group( -COOH)
‒Amino group( -NH2)
‒Side group
118
What is an isomer?
Isomers are molecules that have the same molecular formula, but have a different arrangement of the atoms in space.
119
What is a stereoisomer?
Stereoisomers are isomers that differ in spatial arrangement of atoms, rather than order of atomic connectivity.
120
What is a peptide bond?
Bond between amino acids formed by dehydration synthesis
121
What is the primary structure of protein?
Polypeptide chain
122
What is the secondary structure of protein?
helix and pleated sheet (with three polypeptide strands)
123
What is the tertiary structure of protein?
helix and pleated sheets fold into a 3D shape
124
What is the quaternary structure of protein?
Two or more polypeptides, the relationship of several folded polypeptide chains, forming a protein
125
What is meant by denaturation and what can cause a protein to denature?
Proteins lose their shape and function, can be caused by hostile environments such as temperature and pH affect bonds in proteins
126
What is a conjugated protein?
Consist of amino acids and other organic molecules
–Glycoproteins
–Nucleoproteins
–Lipoproteins
127
What is a nucleotide and what are the basic components of a nucleotide?
```
Make up nucleic acids,
•Nucleotides consist of
–A five-carbon (pentose) sugar
–Phosphate group
–Nitrogen-containing (purine or pyrimidine) base
```
128
What are the components of DNA and what is its basic structure and function?
•Deoxyribonucleic acid–Contains deoxyribose
–Exists as a double helix
–Adeninehydrogen bonds with Thymine
–Cytosinehydrogen bonds with Guanine
•Order of the nitrogen-containing bases forms the genetic instructions of the organism
129
What are the components of RNA and what is its basic structure and function?
```
•Ribonucleic acid
–Contains ribose
–Is single-stranded
–Adenine hydrogen bonds with Uracil
–Cytosine hydrogen bonds with Guanine
•Several kinds of RNA play a specific role in protein synthesis
```
130
What is ATP and what is its structure and function?
* Adenosine triphosphate
* Made of ribose, adenine, and three phosphate groups
* Stores the chemical energy released by some chemical reactions
* Releases phosphate groups by hydrolysis to liberate useful energy for the cell
131
Distinguish between the basic structural characteristics of a prokaryotic and eukaryotic cell
* Prokaryotes consist of one circular chromosome, not in a membrane, no nucleus, no histones, no organelles, peptiglycan cell walls in bacteria, psuedomurein cell walls in archaea, divide by binary fission
* Eukaryotes consist of paired chromosomes in a nuclear membrane, have nucleus, histones, organelles, polysaccharide cell walls when present, divide by mitosis
132
Bacillus
Rod-shaped
133
Coccus
Spherical (round)
134
Coccobacillus
Very short rods that can be mistaken for coccus or bacillus
135
Vibrio
Curved-rod shape (Comma) Spiral bacteria
136
Spirillum
Spiral-shaped (cork-like)
137
Spirochete
Spiral, twisted bacteria
138
Star-shaped
Flat, six-pronged bacteria
139
Rectangular
Rectangular shaped bacteria
140
Diplococci/ Diplobacilli
Pair of Cocci/bacilli
141
Staphylococci
Clusters of cocci
142
Streptococci/ streptobacilli
Chain of cocci/bacilli
143
Tetrads
Groups of four cocci
144
Sarcinae
Cube-like groups of eight cocci
145
What is the compostion of the glycocalyx?
•External to the cell wall
•Viscous and gelatinous
•Made of polysaccharide and/or polypeptide
*Two types capsule or slime layer
146
Distinguish between the capsule and slime layer
Capsule is neatly organized and firmly attached, prevent phagocytosis and a slime layer is unorganized and loose
147
Describe the structure and function of the bacterial flagellum
•Filamentous appendages external of the cell
•Propel bacteria
•Made of protein flagellin
•Three parts:
–Filament: outermost region
–Hook: attaches to the filament
–Basal body: consists of rod and pairs of rings; anchors flagellum to the cell wall and membrane (2 rings in gram + and 4 rings in gram -)
148
Peritrichous flagellar arrangement
Flagella attached all around perimeter of bacterium
149
Monotrichous flagellar arrangement
Single flagella
150
Lophotrichous flagellar arrangement
Cluster of flagella
151
Amphitrichous flagellar arrangement
Flagella extending from opposite ends of bacterium
152
Polar flagellar arrangement
Flagella extending from one or both poles of the cell
153
Explain what is meant by taxis
Flagella allow bacteria to move toward or away from stimuli (taxis) flagella rotate to "run" or "tumble"
154
What is an H antigen?
Flagella proteins are H antigens and distinguish among serovars (e.g., Escherichia coli O157:H7)
155
Axial filaments
* Also called endoflagella
* Found in spirochetes
* Anchored at one end of a cell
* Rotation causes cell to move like a corkscrew
156
Distinguish between fimbriae and pili
•Fimbriae–Hairlike appendages that allow for attachment
•Pili –Involved in motility (gliding and twitching motility)
–Conjugation pili involved in DNA transfer from one cell to another
157
What is the function of the bacterial cell wall?
* Prevents osmotic lysis and protects the cell membrane
* Made of peptidoglycan(in bacteria)
* Contributes to pathogenicity
158
Describe the structure and arrangement of peptidoglycan in the bacterial cell wall
•Peptidoglycan–Polymer of a repeating disaccharide in rows:
▪N-acetylglucosamine (NAG)
▪N-acetylmuramic acid (NAM)
•Rows are linked by polypeptides
159
Describe the gram-positive cell wall
-Thick peptidoglycan
-Teichoic acids
▪Lipoteichoic acid links cell wall to plasma membrane
▪Wall teichoic acid links the peptidoglycan
▪Carry a negative charge
▪Regulate movement of cations
•Polysaccharides and teichoic acids provide antigenic specificity
160
Describe gram-negative cell walls
•Thin peptidoglycan
•Outer membrane–Made of polysaccharides, lipoproteins, and phospholipids
–Contain lipopolysaccharide (LPS)
▪O polysaccharide functions as antigen (e.g., E. coli O157:H7)
▪Lipid A is an endotoxin embedded in the top layer
•Periplasmic space–Contains peptidoglycan
•Protect from phagocytes, complement, and antibiotics
•Porins(proteins) form channels through membrane
161
What is the O antigen?
O polysaccharide functions as antigen (e.g., E. coli O157:H7) part of the LPS layer
162
Describe the cell wall of mycobacterium and nocardia
Acid-fast cell walls
–Like gram-positive cell walls
–Waxy lipid (mycolic acid) bound to peptidoglycan
–Stain with carbolfuchsin
163
How does the cell wall of mycoplasmas and archaea differ from bacteria?
```
•Mycoplasmas
–Lack cell walls
–Sterols in plasma membrane
•Archaea
–Wall-less, or
–Walls of pseudomurein (lack NAM and D-amino acids)
```
164
How do lysozyme and penicillin affect the cell wall of bacteria?
* Lysozyme hydrolyzes bonds in peptidoglycan
| * Penicillin inhibits peptide bridges in peptidoglycan
165
Protoplast
wall-less gram-positive cell, susceptible to osmotic lysis
166
Spheroplast
wall-less gram-negative cell, susceptible to osmotic lysis
167
L forms
wall-less cells that swell into irregular shapes
168
Describe the plasma membrane structure
* Phospholipid bilayer that encloses the cytoplasm
* Peripheral proteins on the membrane surface
* Integral and transmembrane proteins penetrate the membrane
169
What is the fluid mosaic model?
–Membrane is as viscous as olive oil
–Proteins move freely for various functions
–Phospholipids rotate and move laterally
–Self-sealing
170
What is selective permeability?
Allows passage of some molecules ,but not others
171
Simple diffusion
Movement of a solute from an area of high concentration to an area of low concentration
•Continues until molecules reach equilibrium
172
Facilitated Diffusion
Solute combines with a transporter protein in the membrane
| •Transports ions and larger molecules across a membrane with the concentration gradient
173
Osmosis
The movement of water across a selectively permeable membrane from an area of high water to an area of lower water concentration
•Through lipid layer
•Aquaporins (water channels)
•Osmotic pressure:the pressure needed to stop the movement of water across the membrane
174
Active transport
Requires a transporter protein and ATP; goes against gradient
175
Group translocation
Requires a transporter protein and phosphoenolpyruvic acid (PEP); substance is altered as it crosses the membrane
176
Isotonic solution
Solute concentrations equal inside and outside of cell; water is at equilibrium
177
Hypotonic solution
Solute concentration is lower outside than inside the cell; water moves into cell
178
Hypertonic solution
Solute concentration is higher outside of cell than inside; water moves out of cell
179
Describe the structure and location of bacterial genetic material
The Nucleoid
•Bacterial chromosome:circular thread of DNA that contains the cell's genetic information
•Plasmids:extrachromosomal genetic elements; carry non-crucial genes (e.g., antibiotic resistance, production of toxins)
180
Describe the structure and function of the bacterial ribosome
•Sites of protein synthesis
•Made of protein and ribosomal RNA
•70S
–50S + 30S subunits
181
Metachromatic granules (Volutin) *inclusion
Phosphate reserves
182
Polysaccharide granules *inclusion
Energy reserves
183
Lipid inclusions
Energy reserves
184
Sulfur granules *inclusion
Energy reserves
185
Carboxysomes *inclusion
RuBisCO enzyme for CO2 fixation during photosynthesis
186
Gas vacuoles *inclusion
protein-covered cylinders that maintain buoyancy
187
Magnetosomes *inclusion
iron oxide inclusions; destroy H2O2
188
What are endospores and how are they important to the bacteria that can form them?
* Resting cells; produced when nutrients are depleted
* Resistant to desiccation, heat, chemicals, and radiation
* Produced by Bacillus and Clostridium
189
Distinguish between sporulation and germination
Sporulation is endospore formation and germination is when the endospore returns to vegetative state
190
Differentiate between eukaryotic flagella and cilia
* Flagella—long projections; few in number
* Cilia—short projections; numerous
* Both consist of microtubules made of the protein tubulin
191
What is the structure of eukaryotic flagella and how do they move?
* Microtubules are organized as nine pairs in a ring, plus two microtubules in the center (9 + 2 array)
* Allow flagella to move in a wavelike manner
192
Which eukaryotic cell types contain a cell wall and what is the main substance in the cell wall of each of these?
```
–Found in plants, algae, and fungi
–Made of carbohydrates
*cellulose—plants
*chitin—fungi
*glucan and mannan—yeasts
```
193
What is the eukaryotic glycocalyx and what types of eukaryotes have a glycocalyx?
–Carbohydrates bonded to proteins and lipids in the plasma membrane
–Found in animal cells
194
What are the differences in structure between prokaryotic and eukaryotic cell membranes?
•Similar in structure to prokaryotic cell membranes
–Phospholipid bilayer
–Integral and peripheral proteins
•Differences in structure (eukaryotes)
–Sterols—complex lipids
–Carbohydrates—for attachment and cell-to-cell recognition
195
What are the differences in function between prokaryotic and eukaryotic cell membranes?
•Similar in function to prokaryotic cell membranes
–Selective permeability
–Simple diffusion, facilitated diffusion, osmosis, active transport
•Differences in function (eukaryotes)
–Endocytosis—phagocytosis and pinocytosis
196
Endocytosis
Phagocytosis and pinocytosis
197
Phagocytosis
Pseudopods extend and engulf particles
198
Pinocytosis
Membrane folds inward, bringing in fluid and dissolved substances
199
Differentiate between the cytoplasm and cytosol
* Cytoplasm: substance inside the plasma and outside the nucleus
* Cytosol: fluid portion of cytoplasm
200
What is the function of the cytoskeleton and what is it made of?
made of microfilaments and intermediate filaments; gives shape and support
201
Describe the structure and function of the eukaryotic ribosome and how does it differ from the prokaryotic ribosome.
•Sites of protein synthesis
•80S
–Consists of the large 60S subunit and the small 40S subunit
–Membrane-bound: attached to endoplasmic reticulum
–Free: in cytoplasm
•70S–In chloroplasts and mitochondria
*Difference is prokaryotic have small 70S ribosomes
202
What is the structure and function of the nucleus?
–Double membrane structure (nuclear envelope) that contains the cell's DNA
–DNA is complexed with histone proteins to form chromatin
–During mitosis and meiosis, chromatin condenses into chromosomes
203
Differentiate between the rough and smooth ER
* Rough ER:studded with ribosomes; sites of protein synthesis
* Smooth ER:no ribosomes; synthesizes cell membranes, fats, and hormones
204
What is the function of the golgi complex?
* Transport organelle
* Modifies proteins from the ER
* Transports modified proteins via secretory vesicles to the plasma membrane
205
Describe the structure and function of the mitochondria
* Double membrane
* Contain inner folds (cristae) and fluid (matrix)
* Involved in cellular respiration (ATP production)
206
Differentiate between a lysosome and a vacuole
* Lysosomes –Vesicles formed in the Golgi complex–Contain digestive enzymes
* Vacuoles–Cavities in the cell formed from the Golgi complex –Bring food into cells; provide shape and storage
207
Describe the structure and function of the chloroplast
* Locations of photosynthesis
| * Contain flattened membranes (thylakoids) that contain chlorophyll
208
Peroxisome
Oxidize fatty acids; destroy H2O2
209
Centrosome
–Networks of protein fibers and centrioles
| –Form the mitotic spindle; critical role in cell division
210
Explain endosymbiotic theory
–Larger bacterial cells engulfed smaller bacterial cells, developing the first eukaryotes
–Ingested photosynthetic bacteria became chloroplasts
–Ingested aerobic bacteria became mitochondria
211
What is metabolism?
* Metabolism is the buildup and breakdown of nutrients within a cell
* These chemical reactions provide energy and create substances that sustain life
* Although microbial metabolism can cause disease and food spoilage, many pathways are beneficial rather than pathogenic
212
Contrast catabolism and anabolism
* Catabolism:breaks down complex molecules; provides energy and building blocks for anabolism; exergonic
* Anabolism:uses energy and building blocks to build complex molecules; endergonic
213
What is an enzyme and how does it work?
* Enzymes are biological catalysts
* Enzymes act on a specific substrate and lower the activation energy
* Substrate contacts the enzyme’s active site to form an enzyme-substrate complex
* Substrate is transformed and rearranged into products,which are released from the enzyme
* Enzyme is unchanged and can react with other substrates
214
How are enzymes named?
* Names of enzymes usually end in ase;grouped based on the reaction they catalyze
* Oxidoreductase:oxidation-reduction reactions
* Transferase:transfer functional groups
* Hydrolase:hydrolysis
* Lyase:removal of atoms without hydrolysis
* Isomerase:rearrangement of atoms
* Ligase:joining of molecules; uses ATP
215
What is the difference between an apoenzyme and a holoenzyme?
* Apoenzyme:protein portion
| * Holoenzyme:apoenzyme plus cofactor
216
What are the components of an enzyme?
•Apoenzyme:protein portion
•Cofactor:nonprotein component
–Coenzyme:organic cofactor
•Holoenzyme:apoenzyme plus cofactor
217
How does temperature affect enzyme function?
High temperature denatures proteins
•The enzymatic activity (rate of reaction catalyzed by the enzyme) increases with increasing temperature
–To a point
–Enzyme denatured by heat and inactivated
–Cold does not denature enzyme, just slows it down
218
How does pH affect enzyme function?
Extreme pH denatures proteins
The enzymatic activity increases with increasing pH
–To a point
–Enzyme denatured by pH that is too high or too low
219
How does substrate concentration affect enzyme function?
•The enzymatic activity increases with increasing substrate concentration
–To a point
–All active sites on enzymes are filled
–Maximum rate of reaction
220
How do competitive inhibitors affect enzyme function?
•Competitive inhibitors fill the active site of an enzyme and compete with the substrate
221
How do non competitive inhibitors affect enzyme function?
•Noncompetitive inhibitors interact with another part of the enzyme (allosteric site) rather than the active site in a process called allosteric inhibition
*alters the active site
222
What is a redox reaction?
an oxidation reaction paired with a reduction reaction
223
Oxidation
removal of electrons *LEO-loss of electrons oxidation
224
Reduction
gain of electrons *GER-gain electrons reduction
225
What is phosphorylation and how is it used to make energy?
Phosphorylation is the addition of a phosphate to an organic compound
•ATP generated when high energy PO4− added to ADP generates ATP
226
Oxidative phosphorylation
Electrons are transferred from one electron carrier to another along an electron transport chain (system) on a membrane that releases energy to generate ATP
227
Photophosphorylation
* Occurs only in light-trapping photosynthetic cells
* Light energy is converted to ATP when the transfer of electrons (oxidation) from chlorophyll pass through a system of carrier molecules
228
Identify the overall/net inputs (reactants) and outputs (products) for glycolysis
Glucose+ 2 ATP + 2 ADP + 2 PO4-+ 2 NAD+
→2 pyruvic acid+ 4 ATP + 2 NADH + 2 H+
*Overall net gain of 2 ATP/glucose molecule
229
What is used and what is made during the preparatory stage of glycolysis?
–2 ATP are used
| –Glucose is split to form two molecules of glyceraldehyde 3-phosphate
230
What is used and what is made during the energy-conserving stage of glycolysis?
–The two glyceraldehyde 3-phosphate molecules are oxidized to 2 pyruvic acid molecules
–4 ATP are produced
–2 NADH are produced
231
What is the pentose phosphate pathway?
–Uses pentoses and produces NADPH
| –Operates simultaneously with glycolysis
232
What is the Entner-Doudroff pathway and what bacteria utilize it?
–Produces NADPH and ATP
–Does not involve glycolysis
–Occurs in Pseudomonas, Rhizobium, and Agrobacterium
233
Describe the transition step...what are the inputs and outputs?
–Pyruvicacid (fromglycolysis) is oxidized and decarboxylation (lossof CO2) occurs
–CoenzymeA is added, generating AcetylCoA
234
What is the first step of the Krebs cycle?
–AcetylCoA combines with oxaloacetic acid to form citric acid (CitricAcidCycle)
235
What are the products of the Krebs cycle?
–Oxidation of citric acid produces NADH, FADH2, and ATP, and CO2 regenerates oxaloacetic acid
236
Where does the electron transport chain occur for prokaryotes?
Plasma membrane
237
Where does the electron transport chain occur for eukaryotes?
Inner mitochondrial membrane
238
What is meant by chemiosmosis?
•Electrons from NADH passdown the electron transport chain
–Energy used to pump protons across the membrane
–Establishes proton gradient (proton motive force)
•Protons in higher concentration on one side of the membrane diffuse through ATP synthase
–Releases energy to synthesize ATP
239
How many ATPs are generated for each NADH in the electron transport chain?
Each NADH can be oxidized in the electron transport chain to produce 3 molecules of ATP
–NADH dehydrogenase complex
240
How many ATPs are generated for each FADH2 in the electron transport chain?
•Each FADH2 can produce 2 molecules of ATP
| –Quinone (eg ubiquinone)
241
What does NADH reduce in the electron transport chain?
...
242
What does FADH2 reduce in the electron transport chain?
...
243
Where are electrons pumped in the electron transport chain?
Down the electron chain is a series of electron transporters that shuttles electrons from NADH and FADH2 to the final electron acceptor oxygen
244
What is the role of ATP synthase in the electron transport chain?
ATP synthase uses the proton gradient created by the ETC to synthesize ATP from ADP and inorganic phosphate (Pi)
245
What is the final electron acceptor in the ETC?
In aerobic respiration it is O2 and in anaerobic respiration it is not O2
246
What are the three other final electron acceptors that some microbes use besides oxygen and what type of respiration is this?
Sulfate (SO4-), Nitrate (NO3-), and Carbonate (CO3)2-
| *anaerobic respiration
247
What steps of cellular respiration are used in fermentation and which steps are not used?
Glycolysis is used in fermentation but the Krebs cycle and ETC are not used
248
What is produced in lactic acid fermentation?
Lactic acid
249
What is the difference between homolactic and heterolactic fermentation?
–Homolactic fermentation:produces lactic acid only
| –Heterolactic fermentation:produces lactic acid and other compounds
250
What is produced in alcohol fermentation?
ethanol and CO2
251
Explain how triglycerides and phospholipids can be used for energy, what enzymes are used and what steps of cellular respiration are employed?
•Triglycerides and phospholipids are broken down by lipases and phospholipases
–Contribute to virulence in certain microbes, eg.S. aureus
–Glycerol and fatty acids
▪Glycerol →glycolysis
▪Fatty acids undergo beta-oxidation
▪Acetyl groups removed →Krebs cycle; NADH and FADH2 reduced
252
Explain how proteins can be used for energy, what enzymes are used and what steps of cellular respiration are used?
•Proteins broken are down by proteases
–Specific proteases can be used to identify the microbe
–Amino acids shuttled into various stages of respiration
253
What happens in light-dependent (light) reaction of photosynthesis?
conversion of light energy into chemical energy (ATP and NADPH)
254
What happens in light-independent (dark) reactions of photosynthesis?
ATP and NADPH are used to reduce CO2 to sugar (carbon fixation) via the Calvin-Benson cycle
255
What happens in oxygenic photosynthesis?
6 CO2+ 12 H2O + Light energy --> C6H12O6 + 6 H2O + 6 O2
256
What happens in anoxygenic photosynthesis?
6 CO2 + 12 H2S + light energy --> C6H12O6 + 6 H2O + 12 S
257
Where do light dependent reactions occur in prokaryotes?
Infoldings of plasma membrane
258
Where do light dependent reactions occur in eukaryotes?
chloroplasts
259
Distinguish between photosystem I and photosystem II
...
260
Which photosystem is used in cyclic photophosphorylation?
Photosystem I
261
Which photosystem comes first in noncyclic photophosphorylation?
Photosystem II
262
In noncyclic photophosphorylation, how are electrons replaced for photosystem II and photosystem I?
Photosystem II- Electrons lost are replaced by electrons from splitting of water
Photosystem I- electrons are recycled
263
How is ATP made in noncyclic photophosphorylation and what is the final electron acceptor in this process?
ATP is made by an electron transport chain and the final electron acceptor is NADP
264
When is cyclic photophosphorylation used and how is energy generated in this process?
If the need for ATP is greater than the need for NADPH, cyclic photophosphorylation is used and ATP is generated by an ETC
265
What is the alternate name for light-independent reactions?
Calvin cycle or Calvin-Benson cycle
266
In fixation, what important enzyme is used and what reaction does it catalyze?
•Fixation
–RuBisCO enzyme
–CO2 added to RuBP to produce3-PGA
267
In reduction, what is used and what is made?
•Reduction
–6 ATP and NADPH used
–3-PGA converted into G3P
–One G3P leaves the cycle
268
How many G3P are needed for each glucose?
Two G3P to produce glucose
269
What is used and what is made in the regeneration steps?
•Regeneration
–Remaining G3P used to regenerate RuBP
–Uses 3 more ATP
270
Identify the carbon and energy source with one example for photoautotrophs
Energy source-light
Carbon source-CO2
Example- Algae
271
Identify the carbon and energy source with one example for photoheterotrophs
Energy source-light
Carbon source-organic compounds
Example-green and purple nonsulfur bacteria
272
Identify the carbon and energy source with one example for Chemoautotrophs
Energy source- Inorganic chemical
Carbon source-CO2
Example-nitrogen-fixing bacteria (cyanobacteria) / sulfur-oxidizing bacteria
273
Identify the carbon and energy source with one example for chemoheterotrophs
Energy source- Chemical
Carbon source- organic compounds
Example- All animals, most fungi, protozoa
274
What is meant by an amphibolic pathway and give an example
metabolic pathways that function in both anabolism and catabolism *Krebs cycle
275
Distinguish between minimum, optimum, and maximum growth temperature
The growth rates are the highest at the optimum growth temperature for the organism. The lowest temperature at which the organism can survive and replicate is its minimum growth temperature. The highest temperature at which growth can occur is its maximum growth temperature.
276
Psychrophile
Cold-loving
277
Psychrotroph
–Grow between 0°C and 20 to 30°C
| –Cause food spoilage
278
Mesophile
moderate- temperature loving
279
Thermophile
Heat-loving
–Optimum growth temperature of 50 to 60°C
–Found in hot springs and organic compost
280
Hyperthermophile
–Optimum growth temperature > 80°C
281
What pH do most bacteria grow at?
between pH 6.5 and 7.5
282
What pH do most molds and yeasts grow at?
between pH 5 and 6
283
Acidophile
grow in acidic environments (between 1 and 5.5 pH)
284
neutrophile
grow between 5.5 and 8.5 pH neutral environments
285
Alkaliphile
grow in basic environments (between 7.5 and 11.5 pH)
286
Why is a hypertonic environment problematic for microbes?
Hypertonic environments (higher in solutes than inside the cell) cause plasmolysis due to high osmotic pressure
287
Obligate halophile (extreme)
require high osmotic pressure (high salt)
288
Facultative halophile
tolerate high osmotic pressure
289
Identify the molecules that incorporate the element carbon
–Structural backbone of organic molecules
–Chemoheterotrophs use organic molecules as energy
–Autotrophs use CO2
290
Identify the molecules that incorporate the element nitrogen
–Component of proteins, DNA, and ATP
–Most bacteria decompose protein material for the nitrogen source
–Some bacteria use NH4+or NO3-from organic material
–A few bacteria use N2 in nitrogen fixation
291
Identify the molecules that incorporate the element sulfur
–Used in amino acids, thiamine, and biotin
–Most bacteria decompose protein for the sulfur source
–Some bacteria use (SO4)2- or H2S
292
Identify the molecules that incorporate the element phosphorus
–Used in DNA, RNA, and ATP
–Found in membranes
–(PO4)3-is a source of phosphorous
293
Identify the molecules that incorporate the element trace elements
* Inorganic elements required in small amounts
* Usually as enzyme cofactors
* Include iron, copper, molybdenum, and zinc
294
Identify the molecules that incorporate the element organic growth factors
* Organic compounds obtained from the environment
| * Vitamins, amino acids, purines, and pyrimidines
295
Obligate aerobe
* require oxygen
- Growth occurs only where high concentrations of oxygen have diffused into the medium.
- Presence of enzymes catalase and superoxide dismutase (SOD) allows toxic forms of oxygen to be neutralized; can use oxygen.
296
Facultative aerobe
* grow via fermentation or anaerobic respiration when oxygen is not available
- Growth is best where most oxygen is present, but occurs throughout tube
- Presence of enzymes catalase and SOD allows toxic forms of oxygen to be neutralized; can use oxygen.
297
Obligate anaerobe
* unable to use oxygen and are harmed by it
- Growth occurs only where there is no oxygen.
- Lacks enzymes to neutralize harmful forms of oxygen; cannot tolerate oxygen.
298
Aerotolerant anaerobe
* tolerate but cannot use oxygen
- Growth occurs evenly; oxygen has no effect.
- Presence of one enzyme, SOD, allows harmful forms of oxygen to be partially neutralized; tolerates oxygen
299
Microaerophile
* require oxygen concentration lower than air
- Growth occurs only where a low concentration of oxygen has diffused into medium.
- Produce lethal amounts of toxic forms of oxygen if exposed to normal atmospheric oxygen.
300
What is a biofilm and how does it function?
•Microbial communities
•Form slime or hydrogels that adhere to surfaces
–Bacteria communicate cell-to-cell via quorum sensing
•Share nutrients
•Shelter bacteria from harmful environmental factors
301
What are some of the problematic implications of biofilms?
* Found in digestive system and sewage treatment systems; can clog pipes
* 1000x resistant to microbicides
* Involved in 70% of infections–Catheters, heart valves, contact lenses, dental caries
302
Define culture medium
nutrients prepared for microbial growth
303
Define sterile
no living microbes
304
Define Inoculum
introduction of microbes into a medium
305
Define culture
microbes growing in or on a culture medium
306
Why is agar used in solid media?
```
–Complex polysaccharide
–Used as a solidifying agent for culture media in Petri plates, slants, and deeps
–Generally not metabolized by microbes
–Liquefies at 100°C
–Solidifies at ~40°C
```
307
Chemically defined media
*exact chemical composition is known
| –Fastidious organisms are those that require many growth factors provided in chemically defined media
308
Complex media
*extracts and digests of yeasts, meat, or plants; chemical composition varies batch to batch
–Nutrient broth
–Nutrient agar
309
What is a fastidious organism?
those that require many growth factors provided in chemically defined media
310
What is a reducing medium and when should it be used?
–Used for the cultivation of anaerobic bacteria
–Contain chemicals (sodium thioglycolate) that combine O2 to deplete it
–Heated to drive off O2
311
What is a capnophile and what growth conditions does it require?
–Microbes that require high CO2 conditions
–CO2 packet
–Candle jar
312
BSL-1
no special precautions; basic teaching labs
313
BSL-2
lab coat, gloves, eye protection
314
BSL-3
biosafety cabinets to prevent airborne transmission
315
BSL-4
sealed, negative pressure; "hot zone"
| ▪Exhaust air is filtered twice through HEPA filters
316
Selective media
–Suppress unwanted microbes and encourage desired microbes
| –Contain inhibitors to suppress growth
317
Differential media
–Allow distinguishing of colonies of different microbes on the same plate
318
Can a media be both selective and differential?
yes
319
What is an enrichment culture?
* Encourages the growth of a desired microbe by increasing very small numbers of a desired organism to detectable levels
* Usually a liquid
320
Explain how a pure culture might be obtained
* A pure culture contains only one species or strain
| * The streak plate method is used to isolate pure cultures
321
What is a colony?
* A colony is a population of cells arising from a single cell or spore or from a group of attached cells
* A colony is often called a colony-forming unit(CFU)
322
Distinguish between binary fission and budding
Binary fission is bacterial division in which a cell separates into two identical cells (number of cells doubles with each generation) and in budding, a new individual is formed on the old individual cell (eukaryotes such as plants and fungi)
323
What is meant by generation time?
Time required for a cell to divide
| –20 minutes to 24 hours
324
How can the number of cells be determined based on the starting cells and the number of generations (formula)?
of cells X 2^ # of generations
325
Why is graph of bacterial growth represented on a log scale?
Because the number of cells increases rapidly, a logarithmic graph allows you to visualize the complete growth curve.
326
Lag phase
Intense activity preparing for population growth, but no increase in population
327
Log phase
logarithmic ,or exponential, increase in population (binary fission in bacteria/ mitosis in yeast)
328
Stationary phase
Period of equilibrium; microbial deaths balance production of new cells
329
Death phase
Population is decreasing at a logarithmic rate (running out of nutrients/ accumulating toxins)
330
Identify the direct methods for bacterial growth
```
•Direct measurements–count microbial cells
–Plate count
–Filtration
–Most probable number (MPN) method
–Direct microscopic count
```
331
Identify the indirect methods for bacterial growth
* Turbidity—measurement of cloudiness with a spectrophotometer
* Metabolic activity—amount of metabolic product is proportional to the number of bacteria
* Dry weight—bacteria are filtered, dried, and weighed; used for filamentous organisms
332
In plate counts, how are serial dilutions used? Why are serial dilutions important for this method?
To ensure the right number of colonies, the original inoculum must be diluted via serial dilution
*Calculation: # of colonies on a plate X reciprocal of dilution sample = # of bacteria/ml (54 colonies on a plate of 1:1000 dilution = 54,000 bacteria/ml)
333
What is the difference between the pour plate method and spread plate method?
Counts are performed on bacteria mixed into a dish with agar (pour plate method) or spread on the surface of a plate (spread plate method)
334
Explain the filtration method of counting bacteria
* Solution passed through a filter that collects bacteria
| * Filter is transferred to a Petri dish and grows as colonies on the surface
335
In the most probable number method, how is growth estimated?Which types of microbes are counted using this method?
* Multiple tube test
* Count positive tubes
* Compare with a statistical table–Statistical estimating technique–The greater the number of bacteria in a sample, the more dilution is needed to reduce the density to the point at which no bacteria are left to grow in the tubes in a dilution series
* Used with microbes that won’t grow on solid media
* Growth of bacteria in a liquid differential medium is used to identify the microbes (such as coliform bacteria)
336
Describe the direct microscopic count method and the role of the Petroff-Hausser cell counter
•Volume of a bacterial suspension placed on a slide
•Average number of bacteria per viewing field is calculated
•Uses a special Petroff-Hausser cell counter (grid w 25 large squares)
*# of bacteria/ml = #of cells counted/volume of area counted (depthXarea)
337
How is a spectrophotometer used to estimate microbial growth?
Turbidity—measurement of cloudiness with a spectrophotometer, The amount of light absorbed by the bacterial culture is measured.
338
How is dry weight used to estimate microbial growth?
Dry weight—bacteria are filtered, dried, and weighed; used for filamentous organisms
