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MMG 101 > Exam 1 Material > Flashcards

Exam 1 Material Flashcards

1
Q

What is microbiology?

A

microbiology is the study of cellular organisms and acellular biological entities that are too small to see without the aid of a microscope

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2
Q

six basic types of microbes

A

Bacteria: Myobacterium tuberculosis rod-shaped cell
Fungi: Thamnidium filamentous fungus
Algae (protist): desmids, Spirogyra filament, diatoms (golden cells)
Virus: Herpes simplex, cause of cold sores
Protozoa (protist): Vorticella stalked cells…use whirling cilia to feed
Helminths: cysts of roundworm Trichinella spiralis in muscle

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3
Q

microbes are ubiquitous in nature

A

very few microbes cause disease, but they affect all aspects of life on Earth

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4
Q

beneficial microbes

A

no microbes…no life
photosynthesis by cyanobacteria generates ~50% of the O2 we breathe
many microbes are decomposers…recyle nutrients and chemicals in the environment for other organisms

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5
Q

some examples as to why microbes matter

A

Microbes are essential in the gut of ruminants for digestion of grasses
Microbial products act as natural pesticides
In our foods: sausages, sauerkraut, and beer
Bioremediation…used to clean up oil spills
Sewage treatment
Manipulate bacteria to produce:
-Pharmaceuticals: insulin, growth hormone
-Antimicrobials: anti-bacterials…penicillins, anti-virals
-Vaccines against: hepatitis B, human papillomavirus (HPV) (cervical cancer)

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6
Q

microbes in the human body

A

microbiome
~10x more microbes than human cells
~100x more microbial DNA
huge microbial diversity at body sites

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7
Q

microbial pathogens

A

only a minority of microbes can cause disease (EX: pathogens)
pathogen: microbes that causes harm to another

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8
Q

five major modes of transmission

A 
Airborne (respiratory)
Food/waterborne
Sexually (person to person)
Animal/insect
Wound/skin
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9
Q

the effect of plagues on human civilization

A

Disease at a mass level (plagues; pandemics) has…

  • Personal and social effects:
  • -Fear
  • -Panic
  • -Prejudice; hatred
  • -Discrimination
  • Economic effects:
  • -Curtailing travel and commerce
  • -Huge health care costs
  • -Burial costs and time to attend burials
  • -Labor turnover
  • Political effects:
  • -Alters the course of wars
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10
Q

origins of plagues

A

What causes plagues?

  • Changes in human populations and lifestyles
  • -Agricultural revolution: animal domestication and zoonotic diseases
  • -Industrial revolution: crowding of people together with carriers (EX: rats, lie), polluted water and air, and poor public health measures
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11
Q

COVID 19

A

caused by SARS-CoV-2 coronavirus

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12
Q

the black death

A

Bubonic Plague

  • Caused by bacteria Yersinia pestis
  • Discrimination: fear and panic led to hostility against strangers and Jews, who were accused of poisoning wells…900 Jews in Germany were burned alive!
  • Led to new public health measures:
  • -Quarantine (40 days…either died or recovered)
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13
Q

typhus

A

caused by bacteria Ricksettsia prowazekii

transmitted by body lice

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14
Q

cholera

A

Caused by bacteria Vibrio cholerae
Found in contaminated water, food
Cholera toxin: acts on small interesting
-Causes massive secretion of water into intestinal lumen
-Characteristic “rice water” diarrhea
–Can use cholera cots to estimate water loss
Brought about huge changes in public health and sanitation of drinking water

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15
Q

tuberculosis

A

Caused by bacteria Mycobacterium tuberculosis
Romanticized TB, believing it sparked genius
1950s: TB cured by antibiotics, screening tests, and aggressive public health measures
1970s: funds for anti-TB eradication stopped
Today: emergence of multidrug resistance

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16
Q

malaria

A

Caused by protozoan Plasmodium falciparum
Roman fever…malaria (“bad air”)
Office of Malaria Control in War Areas became Centers for Disease Control and Prevention (CDC)

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17
Q

smallpox

A

Caused by orthopoxvirus (variola virus)
Germ warfare by British in the French and Indian War
It so devastated the Native American population that colonists were forced to import slaves from Africa to do work; start of the slave trade

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18
Q

Acquired Immunodeficiency Syndrome

A

AIDS
Caused by HIV retrovirus
Individual has AIDS if:
-Tests positive for HIV or HIV antibodies
-Low CD4 T-cell count
-One or more opportunistic infections or atypical cancers
Risks for acquiring HIV/AIDS:
-Found in sufficient concentrations in blood and semen to cause infection

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19
Q

flu pandemics

A

caused by influenza virus

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20
Q

antoni van leewenhoek

A

the first person to see microbes “wee animalcules”

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21
Q

louis pasteur

A

performed an experiment that disproved the theory of spontaneous generation

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22
Q

Robert Koch and the Germ Theory of Disease

A

Koch’s Postulates-1882
-The microorganism must be present in every case of the disease but absent from healthy organisms
-The suspected microorganisms must be isolated and grown in a pure culture
-The same disease must result when the isolated microorganism is inoculated into a healthy host
-The same microorganisms must be isolated again from the diseased host
Even today, Koch’s postulates should be satisfied before a disease can be attributed to a specific microbe

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23
Q

microscopy

A

the foundation of microbiology today
Microbes can be seen with light, electron, and probe microscopes
Microscopes must be able to:
Produce a magnified image of specimen…magnification
Separate the details in an image…resolution
Make details visible to imaging device or eye…contrast
Metric units of length-most microbes are 0.5-10 um (um=micrometer)

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24
Q

electromagnetic spectrum

A

Wavelength of light used will affect the ability to see microbes:

  • Lower (shorter) wavelength=better resolution (resolving power)
  • -Electron microscopy uses the shortest wavelengths=best resolutions
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25
Q

light refraction and magnification

A

Magnification: apparent increase in size of object
-Occurs when light is refracted (bent) as it passes through a lens
—The bend is what makes it enlarged
–Light microscopy uses glass lens
–Electron microscopy uses magnetic fields to bend electrons
Upper limit for light microscopy ~2000X because of resolution limits
-Beyond that is empty magnification

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26
Q

limits of resolution

A

Resolution: the ability to distinguish two points as separate

  • d: resolving distance (um)=minimal distance between two objects that reveals them as separate entities
  • Resolution increases as d decreases
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27
Q

increasing resolution

A

To increase resolution…

  • Lower the wavelength of incident light (electrons have lowest) OR
  • Increase the N.A. (increase refractive index)-use oil immersion OR
  • -Oil has same refractive index as glass, so refracted light is not lost after traveling through glass cover slip
  • Increase contrast: differences in light intensity between two objects, or between an object and background
  • Staining specimen or phasing light increases contrast
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28
Q

different types of light microscopy

A

bright-field microscopy
dark-field microscopy
phase contrast
differential interference contrast (DIC)

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29
Q

phase constrast micrscopes

A

Treats one set of light rays differently from another set
Light rays in phase produce brighter image
Light rays out of phase produce darker image
Contrast is created when light waves are ½ wavelength out of phase

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30
Q

fluorescence microscopy

A

UV light is absorbed by specimen and emitted as longer, visible wavelength
-Increases resolution and contrast

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31
Q

fluorochromes

A

Fluorochrome: fluorescent molecule

-There are molecules that can be attached to proteins in your cell or they bind to structures in the cell

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32
Q

confocal laser-scanning microscopy

A

UV lasers illuminate fluorescent chemicals in a single focal plane that is no thicker than 1.0 um…optical slice
-Not that powerful for bacteria but can be very powerful/helpful when looking at things such as tumor cells

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33
Q

electron microscopy

A

Light microscopes cannot resolve structures closer than ~200 nm because shortest wavelength of visible light is ~400 nm
Accelerated electrons have wavelengths of 0.01 nm-0.001 nm, so electron microscopes have greater resolving power and greater magnification
Use heavy metals (EX: osmium, tungsten) to stain structures or background
This has to be done in a vacuum because electrons are absorbed by air
Three types:
-scanning electron microscopy
-transmission electron microscopy
-cryo electron microscopy

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34
Q

scanning electron microscopy (SEM)

A

Sample is coated with metal (EX: platinum, gold)
Primary electrons knock electrons off metal, producing secondary electrons that are detected, can only see outside of cells

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35
Q

transmission electron microscopy (TEM)

A

Electrons pass through specimen, then through magnetic field that focuses them onto fluorescent screen
Can see inside cells
Dark areas are result of electron absorption by specimen
Must be done with dead samples in vacuum because air absorbs electrons
Gives you information at the structural level but not the molecular level

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36
Q

cry-electron microscopy (Cryo-EM)

A

Imaged without dehydration or chemical fixation…lessens disruption or distortion of biological structures
Can do cryo-TEM, cryo-SEM, cryo-electron tomography (cryo-ET)

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37
Q

staining

A

Increases contrast and resolution by staining specimens with dyes
-If the dye can bind to a structure it will show up as that color
Dyes: salts composed of cation and anion…one has chromophore for color
Basic, cationic (+) dyes…stain (-) charged structures
-Used more commonly
Acidic, anionic (-) dyes…stain (+) charged structures
Simple stains (crystal violet, methylene blue, safranin)

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38
Q

Hans Christian Gram and the Gram Stain (1884):

A

Gram stain: differentially stains bacterial cells
Initial, most important stain used to identify bacteria in clinical samples
Most bacteria are either Gram-positive or Gram-negative
-This distinction tells you about the structure and how to potentially treat an infection with that bacteria

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39
Q

differential and special stains

A 
differential stains
-acid-fast stain
-endospore stain
special stains
-capsule stain
-flagellar stain
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40
Q

evolution of life on earth

A

origin of life:

  • bacteria have been around the longest
  • cyanobacteria triggered the “great oxidation event”
  • -allowed for the evolution of aerobic life…mammals
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41
Q

prokaryotes

A

do not have membrane bound organelles

  • bacteria
  • archaea
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42
Q

eukaryotes

A

contain membrane bound organelles including a “true nucleus”: eykarya

  • yeast
  • fungi
  • algae
  • protozoa
  • plants
  • animals
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43
Q

hierarchical arrangement in taxonomy

A

taxonomy: biological classification; Bergery’s Manual of Systematic Bacteriology…gold standard
Polyphasic taxonomy: use of phenotypic, genotypic, and phylogenetic features to assign a genus and species
Genus: well-defined group of one or more species that is clearly separate from other genera (capitalized)
Species: collection of microbes that share many stable properties and differ significantly from other groups of microbes
Strain: descendants of a single, pure microbial culture

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44
Q

phonetic criteria for classification of microbes

A

Phenetic (classical) criteria: based on morphological, physiological, biochemical, and ecological characteristics (phenotype)

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45
Q

traditional whittaker system of classification (1969)

A

Based on:
Cell structure and type (prokaryote vs eukaryote)
Nature of body organization (unicellular vs multicellular)
Nutritional type (autotroph vs heterotroph)

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46
Q

phylogenetic criteria for classification of microbes

A

Phylogenetic (molecular) criteria: based on DNA, RNA, and protein sequence and structure
Carl Woese compared bacterial 16S rRNA sequences to classify microbes (18S rRNA in eukaryotic microbes)
-Sequence the DNA gene that encodes the 16S/18S rRNA found in ribosome small subunit (SSU)
->98% identity between 16S rRNAs defines a species

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47
Q

16S rRNA Gene and Structure

A

16S rRNA gene is PCR amplified from microbe of interest

Amplification across variable regions can distinguish between species

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48
Q

Carl Woese and the Three Domains of Life:

A

Bacteria: majority of known prokaryotes
Archaea: prokaryotes that live in extreme environments
Eukarya (eukaryotes)…non-prokaryotic microbes
Last Universal Common Ancestor (LUCA; foot of tree)maps to earliest region of bacterial branch
Archaea and Eukarya evolved independently of Bacteria

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49
Q

microbial growth and diversity

A

Most (not all) microbes reproduce by asexual binary fission
Growth is affected by…
-Nutrient, H2O availability
-Temperature
-pH
-Oxygen
Genetic diversity: change in genetic composition
-Mutations: heritable change in DNA…vertical gene transfer (VGT)
-Horizontal gene transfer (HGT): unidirectional DNA movement from one cell to another
-Both mutations/VGT and HGT can give rise to antimicrobial resistance and virulence

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50
Q

microbial evolution through mutation

A

anagenesis
-Genetic drift (microevolution) of core genome
-Small, random genetic changes over generations
-Drives speciation or extinction
–Only adaptive mutants conferring growth advantage are selected
Stable ecotype model:
-Genetically similar microbes are in distinct ecosystems
-Members of one ecosystem diversify and gain adaptive mutation to compete for resources extinction occurs in other ecosystems

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51
Q

microbial evolution through horizontal gene transfer

A

HGT: causes abruptly phenotypic changes

  • Constantly occurring in nature…not all microbes exhibit HGT
  • Foreign DNA can be acquired from the environment (lysed cells), phage infection or plasmid mobility, and bacterial conjugation
  • Foreign DNA cna contain virulence genes, antimicrobial resistance genes, metabolic genes, etc
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52
Q

Microbial Diversity: Bacteria and Archaea:

A

Unicellular…lack membrane-bound organelles
Ubiquitous in environment…some found in extreme environments
Bacteria can be pathogenic to humans below
Archaea are not pathogenic

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53
Q

Microbial diversity: protists

A

Protists: Eukarya

  • Protozoa:
  • -Apicomplexans
  • -Amoebas
  • -Flagellates
  • -Ciliates
  • Algae:
  • -Dinoflagellates
  • -Diatoms
  • -Green algae
  • Slime molds
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54
Q

microbial diversity: protozoa

A

unicellular protists

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55
Q

microbial diversity: algae and phytoplankton

A

Unicellular (phytoplankton) or multicellular (algae) protists
Capable of photosynthesis
Simple reproductive structures
Categorized by pigmentation, storage products, and composition of cell wall

56
Q

microbial diversity: fungi

A 
Unicellular and multicellular eukaryotes
Get food from other organisms...decomposers
Several groups:
-Moulds: multicellular; grow as hyphae
-Yeats: unicellular
-Mushrooms: multicellular
57
Q

bacteria cell structures

A 
No membrane bound organelles
Internal and external structures
-Cell wall
-Plasma membrane
-Flagella 
-fimbriae/pili
-glycocalyx/capsule
-Cytoskeleton
-Endospores
-Storage inclusions
-DNA nucleoid
58
Q

bacteria cell wall functions

A

Target of many antibacterials
-EX: penicillins, cephalosporins
Provides protection from osmotic turgor pressures
-Most bacteria live in low solute (high solvent H2O) conditions compared to high solute (low solvent H2O) inside cell…this creates osmotic turgor pressure
-Without cell wall, the cell will swell as H2O enters (osmosis)…eventually the membrane will rupture (lysis)

59
Q

bacteria cell wall: peptidoglycan (Murein)

A

Polymer of many identical subunits

NAM sugar + NAG sugar + 5 amino acids

60
Q

Bacteria Cell Wall: Sensitivity to Lysozyme:

A

Beta(1-4) linkage between NAM and NAG sensitive to lysozyme…human bacteriolytic enzyme

61
Q

Peptidoglycan Shape and Peptide Cross-Links:

A

Peptide cross-liks:

  • Covalent linkage between amino acids that connect sugar strands…form the rigid peptidoglycan structure
  • Linkage can be direct between the amino acids on different strands (Gram negative) or through peptide interbridges (Gram positive)
62
Q

Formation ofPeptide Cross-links: Transpeptidation:

A

Transpeptidation: formation of peptide cross links
Catalyzed by bacterial penicillin-binding protein (PBP) enzymes
PBPs are inhibited by penicillin and its derivatives (Beta-lactams)
Resistance to penicillins can arise from mutations in PBPs…MRSA

63
Q

Synthesis of Peptidoglycan:

A

NAM-NAG-pentapeptide precursors are inserted into growing wall
Bactoprenol transports precursors across plasma membrane

64
Q

generation of cell shape

A

peptidoglycan synthesis

65
Q

Turnover of Cell Walls

A

Autolysins:

Same activity as human lysozyme

66
Q

Walls of Gram-positive vs Gram-negative Bacteria

A

Gram stain: differentially stains bacterial cells
-Gram-positive bacteria: ~90% of wall is peptidoglycan
Gram-negative bacteria: ~10% of wall is peptidoglycan

67
Q

Gram-Positive Cell Walls:

A

~25 layers of NAm-NAG sugar strands
Teichoic and lipoteichoic acids: provide negative charge
Can induce septic shock in humans

68
Q

Mycobacterium Cell Walls:

A

Contain mycolic acid residues

  • Hydrophobic long-chain fatty acids…allows cells to survive in teh environment for long periods of time
  • Make up ~60% of total cell wall mass
  • Responsible for “acid fast” properties of Mycobacterium tuberculosis and Mycobacterium leprae
69
Q

Gram-Negative Cell Walls:

A

Thin peptidoglycan layer surrounded by outer membrane
Outer membrane: lipids, lipoproteins, and lipopolysaccharide (LPS)
-Connected to peptidoglycan by Braun’s lipoprotein
Periplasmic space: 20-40% of cell volume…contains many proteins

70
Q

Lipopolysaccharide (LPS) Components:

A

Lipid A: embedded in outer membrane
Core polysaccharide: ~10 sugars
O-antigen: sugars that extends outward from core…great diversity in sugars between Gram-negative bacteria
LOS: lipooligosaccharide…missing O antigen

71
Q

LPS function

A

Creates a permeability barrier
Used for attachment an biofilm formation
Protects Gram-negative bacteria from host defenses
O-antigen: contains highly variable sugars
Acs as endotoxin
Lipid A binds to host LPS-binding (LBP)
Causes fever, inflammation, and septic shock…death

72
Q

Gram Negative Cell Antigens

A

Proteins or sugars attached to Gram-negative cells

  • O antigens…cell wall sugars
  • H antigens…flagella
  • K antigens…capsule
73
Q

Archaea Cell Walls:

A

Archaea walls:

  • No peptidoglycan nor LPS
  • Most commonly contain S-layer
  • -Regularly structured layer of proteins and glycoproteins
74
Q

Eukaryotic Cell Walls:

A

Fungi and algae have cell walls…do not contain peptidoglycan
Fungi: 80-90% polysaccharide
-Chitin: polymer of NAG
Algae: similar to plant walls but contains diverse constituents:
-Cellulose: glucose polymer
-Calcium carbonate: coralline algae
-Silica (sand): diatoms

75
Q

bacterial cell membranes

A

Phospholipid bilayers embedded with proteins
Amphipathic phospholipids form bilayer in aqueous environment
Fatty acids interact through hydrophobic interactions
Phosphate groups interact with aqueous environment (inside and outside cell)

76
Q

sterols and hopanoids

A

Cholesterol: steroid with hydroxyl (-OH) functional group-inserts itself in phospholipid bilayer
-Only found in eukaryotic membranes
-Planar molecule…provides rigidity to membranes
Hopanoids: sterol-like molecules found in bacterial cell membranes
Ergosterol: derivative of cholesterol only found in fungal membranes
-Primary target for antifungal drugs-longer term to breakdown cholesterol

77
Q

archaea membranes

A

chemically unique
-ether linkages connect glycerol to isoprene units, not fatty acids
-can form bilayers and monolayers…very resistant to disruption
much more stable to heat, cold, etc…
held together by covalent bonds and is much more resistant

78
Q

membrane proteins

A

membranes are fluid mosaics with viscosity of light-grade oil
embedded proteins are either integral or peripheral
-integral: span bilayer partially or completely (transmembrane)
-peripheral: anchored into bilayer by lipid tails
they are permeable: let things in and out but are discriminatory

79
Q

membrane functions

A

Passage of substance into and out of cell…selective permeability
Anchors proteins needed for transport, energy
-Transport proteins are needed to bring solutes into cells against a concentration gradient (usually higher concentration inside cell)
-Energy production in bacteria…proton motive force (PMF)
–An electrical gradient, or voltage, is created by movement of charged H+ ions across membrane
Moves high to low concentration=no energy expenditure
-If moving low to high energy is needed

80
Q

Concentration-Dependent Transport Mechanisms

A

Cells never want to be in equilibrium because they will die
Simple diffusion: movement from high to low concentration
-No energy is required
-Concentration reaches equilibrium
Facilitated diffusion: channel protein (permease) binds to molecule and conformational change allows transport
-No energy is required
-Concentration reaches equilibrium
Active transport: movement against concentration gradient
-Greater concentration inside cell (up to 1000X)
-Energy is required
-Concentration does not reach equilibrium

81
Q

active transport mechanisms

A 
simple transport
-Molecule is not altered
-Energy: proton motive force (PMF)
Group translocation:
-Molecule is chemically altered during transport
-Energy: PEP
ABC transport:
-ATP-Binding Cassette
-Molecule is not altered
-High affinity (~1uM)...able to transport very small amounts
-Energy: ATP hydrolysis
82
Q

Protein Secretion and Translocation

A

Secretion: protein movement to outside the cell
Translocation: movement into cell membrane or periplasmic space
~20% of Gram-positive and Gram-negative polypeptides (~800 in E. coli)
Sec pathway (SecYEG proteins):
-Can occur post-translational or co-translational (SRP)
-Translocates unfolded proteins
Tat pathway (TatABC proteins):
-Only post-translational
-Translocates folded proteins

83
Q

Protein Secretion in Gram-Negative Bacteria

A

Additional mechanisms are needed for secretion across the outer membrane of Gram-negative bacteria-has to get through both membranes
-Every cell needs at least one of them but can have more than one
-Toxins and virulence factors are secreted this way!!
No gram negative does all of them but they are all represented in gram negative

84
Q

type 1 secretion system

A

T1SS: uses ABC proteins/ATP hydrolysis

  • Linked to outer membrane barrel protein through membrane fusion protein (MFP)
  • Can secrete proteins up to 1000 aa
  • Doesn’t use Sec/Tat pathways
85
Q

type 2 secretion system

A

T2SS:uses two-step process

  • Use two step process for multi-subunit toxins
  • Uses Sec/Tat pathways and general secretory proteins
  • Secreted proteins fold in periplasm prior to release from cell
  • Easier to put it together in periplasmic space and then secrete it together
  • Subunit: polypeptide
86
Q

type 3 secretion system

A

T3SS: similar to T6SS

  • Used by pathogens E. col, Yersinia, Shigella, Salmonella
  • Uses “injectisome” to insert proteins directly into host cell
  • Complex multiprotein complex-“needle” consists of ~20 proteins
  • -Never gets exposed to our defense systems/outside of cells because it travels into the needle from one host cell and directly into a new cell
  • To get to human cells
87
Q

type 4 secretion system

A

T4SS: used by human and plant pathogens

  • Can secrete proteins and DNA
  • Secreted proteins or DNA goes through both membranes and then into host cell
  • -Many plant pathogens
  • Complex!
88
Q

type 5 secretion system

A

T5SS: “autotransporter”
Uses Sec and Tat pathways
Passenger domain and pore-forming beta-domain

89
Q

type 6 secretion system

A

T6SS: similar to T3SS
Used to attack eukaryotic cells and other bacteria…competitive advantage in growth environment
Injects protein effectors that lead to cell death

90
Q

bacterial cytoskeleton

A

Recently identified
Function in cell division, protein localization, and determination of cell shape
Tubulins, Actins, Intermediate Filaments

91
Q

Microbial Motility

A

Bacteria: flagellum (singular)/flagella (plural)
If you have one or more flagella the price is energy/atp because energy/atp is required to create the structures as well as to regulate the movement
Eukaryotic microbes:
Pseudopodia (Amoeba)
Cilia (Balantidium coli)
Flagella (Leishmania)

92
Q

Bacterial Motility-Flagellum

A

Flagellum: filamentous structure attached to cytoplasmic membrane
The number of flagella they have determines the way they move
How the flagella moves dictates the movement
Monotrichous (polar): flagellum at one end of cell
EX: Pseudomonas
Amphitrichous: flagella at both ends of cell
Lophotrichous: many flagella at both ends of cell
Peritrichous: flagella around entire periphery of cell

93
Q

Structure of Bacterial Flagellum:

A

Filament: rigid, helically-shaped polymer of protein flagellin
Hook: different protein
Connects filament to motor (basal body)
Basal body: rod that passes through two (Gram positive) or four (Gram negative) rings
Anchors flagellum in membrane
Motor (Mot) and switch (Fli) protein surround inner rings

94
Q

Synthesis of Bacterial Flagellum:

A

Complex process involving many proteins
New flagellin molecules are transported through the hollow filament using system similar to T3SS
Filament subunits, self-assemble with help of filament cap protein
Growth if from tip, not base

95
Q

Flagella Movement:

A

Flagella spin like propellers
Variable rotation rate affects speed, direction
Rate: up to 1100 revs/sec=12,000 rpm
Cell movement: 50-60 body lengths/sec
Cheetah…25 body lengths/sec
Energy for “motor” is derived from proton motive force (PMF)
Flagella can rotate in both directions
Forward run…counter-clockwise (CCW) rotation

96
Q

Chemotaxis and Cell Movement:

A

Bacteria sense gradients of chemicals or physical agents (light) and move (taxis) towards attractants and away from repellents
Temporal sensing:
Sample environment temporally for gradients of attractants or repellant
Move through runs and tumbles
At a certain time period they will sense their environment. Based on what they sense at that time will dictate whether they go clockwise or counter clockwise
Respond to environment chemicals

97
Q

Chemotaxis Receptors-MCPs

A

Chemicals bind to receptor proteins on cell surface, signaling flagellum to rotate one way or another
MCPs: Methyl-accepting Chemotactic Proteins
Transmembrane receptors that bind attractants and/or repellants
Located around the periphery of cells
Different bacteria have different numbers and types depending on what they attract to and repel from
E.coli has 5 MCPs

98
Q

Chemotaxis Signal Transduction:

A

MCPs transduce signal to CheA kinase
CheA kinase outs phosphates onto other proteins-the protein in this scenario is CheY
Depending on if CheY is phosphorylated or not will tell the switch to spin clockwise or counterclockwise
Responds to something inside the cell, signals a kinase, adds a phosphate to CheY and will spin in one direction
CheA phosphorylates CheY protein…generates phospho-CheY
phospho-CheY interacts with switch proteins in flagellar motor to control spin direction and speed

99
Q

Spirochete Movement:

A

Clinically significant spirochetes
Treponema pallidum…syphilis
Borrelia burgdorferi…Lyme disease
Tightly coiled (corkscrew) morphology
Depends on endoflagella
Numbers (2-100) vary by species
Contained in axial filaments…run lengthwise in periplasmic space between inner and outer membranes
These flagella are between the two membranes-not outside
They still rotate but are caught between the two membranes which causes it to look more like a twisting/corkscrew movement and not a propeller

100
Q

Eukaryotic Flagella:

A

Flagella: made of tubulin microtubules and dynein (motor)
Whip-like motion (unlike bacteria)
Encased in cell membrane (unlike bacteria)
Cilia: similar to flagella, but shorter and many more
Beat like oars

101
Q

Fimbriae/Pili:

A

Fimbriae/pili: filamentous polymer of pilin proteins
Numerous hair-like structures over cell surface
Function in attachment to surfaces and other cells
EX: Neisseria gonorrhoeae cells without pili are avirulent (cannot cause gonorrhea)
Conjugation pilus: brings cells together so that DNA from the piliated (donor) call can move
Specialized form of pili
Single pilus connects two cells
Brings cells together so that DNA from the piliated (donor) cell can move

102
Q

Generation of Fimbriae/Pili:

A

Each piliated bacteria have different types of fimbriae/pili

Adhesion pili have a cap protein at tip that recognizes those protein

103
Q

Capsules

A

Capsule (can also be called glycocalyx)
Polysaccharides, polypeptides secreted by cells
Different species have different sugars
Functions:
Attachment to host cell surfaces
Anti-phagocytic…protects pathogen from host macrophage and neutrophils
Allows survival and dissemination in bloodstream
Capsules are a cell produced structure

104
Q

Bacterial Storage Inclusions:

A

Inclusions (granules):
Used to store nutrients, energy, structural building blocks
Not membrane-bound organelles
Glycogen (polymerized glucose): energy carbon
Poly-beta-hydroxybutyrate: energy, carbon (lipids)
New form of biodegradable plastic!
Polyphosphates: inorganic phosphate…DNA, RNA, ATP
Iron magnetite (Fe3O4): magnetotaxis
Sulfur: (amino acids; energy)

105
Q

Bacterial Endospores:

A

Endospores: form inside some Gram-positive soil bacteria
EX: pathogenic Clostridium spp., Bacillus spp.
Resistant to heat, drying, harsh chemicals
Designed for protection when nutrients are low or when conditions become intolerable for cell
Can remain dormant for thousands of years
Germination: spore is converted back into growing cell

106
Q

Bacterial Sporulation:

A

Sporulation: process of forming endospore
Can take ~8-10 hours (Bacillus subtilis)
>200 gene products involved
Sporulation genes are turned on and growth genes are turned off

107
Q

Microbial Nutrition:

A

Cell growth requires the import and/or synthesis of nutrients to make macromolecules (anabolism)
Monomers: precursor molecules that form macromolecules
Polymers: macromolecules made up of monomer building blocks
Lipids
Carbohydrates
Proteins
Nucleic acids

108
Q

Nutrition Needed for Anabolism:

A

Macronutrients: required in large amounts
Carbon
Hydrogen
Oxygen
These three are the backbone of all organic molecules…sugars, lipids, proteins, DNA, RNA
Nitrogen: proteins, DNA, RNA
Phosphorous: DNA, RNA, lipids
Sulfur: amino acids, vitamins
Ions (salts):
Potassium (K)
Magnesium (Mg)
Sodium (Na)
Calcium (Ca)
Iron (Fe)
Cofactors for enzymes, stabilize protein and cell wall structures, regulate osmolarity, etc
Micronutrients and growth factors: required in small amounts
Metals and vitamins needed as cofactors for enzymes
Chromium (Cr), Manganese (Mn), Nickel (Ni) etc

109
Q

Microbial Growth:

A

Microbial Growth: Increases in numbers of microbes…not size
Reproduction results in growth
Asexual binary fission: equal division into two…cellular constituents (DNA, protein, etc) are doubled
Partitioning of cellular constituents (DNA, protein, etc…) into two cells and separating two cells form each other by cytokinesis

110
Q

Alternate Modes of Reproduction:

A

Not all microbes divide by binary fission

111
Q

Exponential Growth:

A

Exponential (logarithmic) growth: cells double their number within a constant generation time
Affected by nutrients, temperature, environmental conditions
Generation times vary between organisms

112
Q

Measurements of Microbial Growth:

A

Viable cell count:
Plant count…only live cells grow
Advantage: sensitive and accurate
Disadvantages: time consuming
Total cell count:
Microscopic count
Disadvantages: dead cells look like live cells; tedious
Turbidity: cells scatter light; more (or bigger) cells more scatter
Spectrophotometer measures the optical density (O.D.) of culture
Using O.D. and plate count at same time, you can equate a given O.D. with actual cell number (standard curve)
Used to determine the number of cells in culture by its O.D. reading
Advantage: quick and easy (most frequently used method of quantifying cell numbers in the research laboratory)
Disadvantages: larger cell bias and dead cells scatter light too

113
Q

Typical Growth Curve:

A

Lag phase: adaptation to new growth medium…no immediate increase in cell numbers occurs
Exponential (log) phase: microbes are growing and dividing at the maximal rate posible given their genetic potential
Stationary phase: where population growth ceases; # of live cells=dead cells
Death phase: the number of viable cells declines exponentially…loss of nutrients and build-up of toxic wastes
Long-terms stationary phase: actively reproducing cells evolve to use the nutrients released by dying cells and to tolerate the accumulated toxins…marked by successive waves of genetically

114
Q

Environmental Factors Affecting Growth:

A

temperature
osmotic effects
pH
oxygen

115
Q

Environmental Factors Affecting Growth: temperature

A

Affects enzymatic reactions (metabolism), protein folding, membrane structures, protein interactions, and permeability
Uses of temperature to control bacterial growth:
Refrigeration and freezing for food storage
heating/boiling for sterilization and food preparation
Human fevers
Temperature ranges for bacteria:
Most pathogens: 25-40ish degrees C
Psychrophiles: -5 degrees C to 20 degrees C
Psychrotrophs: -1 degrees C to 35 degrees C
Mesophiles: 13 degrees C to 45 degrees C
Thermophiles: 42 degrees C to 80 degrees C
Hyperthermophiles: 65 degrees C to 105 degrees C

116
Q

Environmental Factors Affecting Growth: osmotic effects

A

High solute concentrations (EX: [Na+]; sugar) outside the cell-cell cannot compensate…growth is inhibited
Basis for salt preservation (bacon, salt pork) and sugar preservation (jellies, honey)
Cell maintain osmotic balance by either pumping K+ ions into cell or synthesizing compatible solutes (EX: sucrose, glycerol, amino acids) inside cell

117
Q

Environmental Factors Affecting Growth: pH

A

Affects protein structure, membrane structure, and proton (H+) gradient essential for proton motive force

118
Q

Environmental Factors Affecting Growth: oxygen

A

Aerobes: utilize O2 at ambient concentration (~21% in air)
Anaerobes: tolerate O2 poorly or not at all
Low O2 availability…canned foods (botulism), intestinal tracts, mouth (gingiva), deep underground, etc…

119
Q

Reduction of O2 Generates ROS

A

Reduction of O2 to H2O generates reactive oxygen species (ROS)
Human neutrophils use ROS to kill invading microbes…respiratory burst
Aerobes have enzymes that destroy these toxic intermediates
Anaerobes don’t have these enzymes…in presence of oxygen, these compounds build up toxic levels

120
Q

Enzymes that Protect Against ROS:

A

Staphylococcus spp. Have catalase enzymes, but Streptococcus spp. don’t
*Know catalase-detoxifies hydrogen peroxide

121
Q

Automated Biochemical Testing:

A

Tests for fermentation of different sugars

122
Q

Control of Microbial Growth:

A

There are many physical, chemical, and mechanical methods that can destroy or reduce the number of undesirable microbes in a given area (decontamination)

123
Q

Microbial Control Terminology:

A

Sterilization: Complete removal or destruction of all viable microbes…used on inanimate objects
Including endospores
Disinfection: destruction or removal of growing microbes but NOT bacterial endospores…used only on inanimate objects
Antisepsis: chemicals applied to body surface to destroy or inhibit growth of microbes
Chemotherapy: chemicals used internally to kill or inhibit growth of microbes within host
Antibiotic: produced by microbes…naturally occurring
Antimicrobial agent: can be antibiotic or chemically synthesized

124
Q

-static vs -cidal Inhibition:

A

-static: reversibly inhibits growth…bacteriostatic, fungistatic, virustatic
-cidal: kills microbes…bactericidal, fungicidal, virucidal
-lytic: kills by lysing cells…bacteriolytic, fungilytic
External (to host) control methods: physical and chemical
Internal (to host) control methods: antimicrobial agents/antibiotics

125
Q

microbial death rates

A

Must susceptible cells die first, followed by hardier (resistant) cells
Therefore, must use antimicrobial agent until all cells are dead
Effectiveness of antimicrobial agents:
High-level: kills all pathogens, including endospores
Intermediate-level: kills fungal spores, protozoan cysts, viruses, pathogenic bacteria
Low-level: kills growing bacteria, fungi, protozoa, some viruses

126
Q

factors that affect death rates

A 
Number of microbes
Type of microbes in the population
Temperature and pH of environment
Concentration or dosage of agent
Mode of action of the agent
Presence of solvents, organic matter, or inhibitors
127
Q

Targets and Mechanisms of Action

A

Four categories of cellular targets:
Cell wall: alcohols, detergents, antimicrobials (penicillins)
Cell membrane: detergents, surfactants
Protein or nucleic acid synthesis…block replication, transcription, and/or translation…antimicrobials, radiation, chemicals
Protein structure/function…denature (unfold) proteins…alcohols, phenols, heavy metals
Loss of secondary, tertiary, and quaternary structures but not primary

128
Q

Physical Control-Heat:

A

Most widely used method of sterilization…moist and dry heat
Moist heat is most efficient…steam heat (autoclave)
High temperature melts cellular membranes and denatures proteins
Efficacy depends on time and temperature
Dry heat: usually carried out in some type of oven

129
Q

Steam Heat-Autoclave:

A

Uses steam under pressure
Pressure causes water to boil at higher temperatures usually 121 C for 15 min or more
Sterilizes all pathogenic microbes, including endospores!

130
Q

Reduced Heat-Pasteurization:

A

Used for milk, beer, wine, ice cream, yogurt, fruit juices

NOT sterilization…heat-tolerant and thermophilic microbes, and endospores surviv

131
Q

Physical Control-Radiation:

A

Electromagnetic radiation: microwaves, UV light, gamma-rays, X-rays, high energy electrons
Microwaves: thermal effects
Non-ionizing radiation…UV light
Creates thymine dimers…blocks DNA replication
Surface sterilization…doesn’t penetrate solids
Ionizing radiation…X-rays, gamma rays, electrons
Cause DNA and protein damage
Used to sterilize heat-labile liquid and solid material, such as growth serum, antibiotics, tissues, surgical supplies, some foods

132
Q

Chemical Control-Disinfectants and Antiseptics:

A

Disinfectant: used on inanimate objects
EX: floors, tables, bench tops, walls
Dangerous if used internally
Antiseptics…used on skin but not internally
Sufficiently non-toxic to tissues
Non-specific towards microbe…have one, or both, of these mechanisms:
Disrupt phospholipid membranes
Remove or interact with lipids
EX: detergents, lipid solvents
Alter proteins irreversibly
Oxidants, alkylating agents, sulfhydryl-reaction reagents

133
Q

Phenols and Alcohols:

A

Phenols: first antiseptic used
Denatures proteins and disrupts membranes
Phenol is too caustic…phenolics are used
Alcohols:
Denatures proteins and disrupts membranes
Ethanol and isopropyl alcohol
Effective against viruses but not endospores
Phenolics and alcohols are the two biggest antispetics

134
Q

Halogens:

A

Halogens: iodine, chlorine, bromine, fluorine
Denatures proteins by disrupting disulfide bonds
Chlorine and bromine: water treatment; fluoride in drinking water
Iodine: 2% tincture in alcohol (7% is toxic)

135
Q

Surfactants:

A

Surfactants: “surface active” chemicals
Reduce solvent surface tension…more effective at dissolving solutes
Soaps: cleansing action…washes off microbes (degerming)
Germicidal soaps give persistent effects
Detergents: amphipathic…disrupts membrane permeability
Cationic (+) quaternary ammonium ions (quats) are used most
None of these are sterilizing agents

136
Q

Oxidizing Agents:

A

Oxidizing agents:
Produce ROS…oxidizes proteins
Hydrogen peroxide…disinfects and sterilizes objects
Neutralized by catalase, so not useful for treating wounds
Ozone: treatment of drinking water

137
Q

Heavy Metals:

A

Heavy metal ions:
Alter 3-D shape of proteins…inhibits their function
Mercurials: bind to -SH groups of enzymes
Copper: controls algal growth in fish tanks, reservoirs, swimming pools
Do not affect membrane

MMG 101 (10 decks)

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