lecture3 and 4 Flashcards
microbial growth (79 cards)
1
Q
How can bacteria and archaea reproduce?
A
- binary fission (one cell becomes two through asexual reproduction) - parents stay
- budding or multiple fission ( divides into multiple equal-sized daughter cells and parents breakaway)
2
Q
What is growth?
What does it refer to?
how can growth be measured?
A
- increase in cells that is caused by an increase in cell size and number
- this refers to population growth
- spectrophotometer (measures light at different wavelengths - only an issue when solution becomes too dense, so it’ll compete)
- The proper way is to dilute and do serial dilution
3
Q
- when is a microbial growth curve observed?
what is a batch culture
A
- when microbes are grown in liquid culture
- growth of microbes in a closed culture vessel with a single batch of medium (w/o adding fresh or removing
old medium
4
Q
what are the five phases of a microbial growth curve?
A
- Lag phase (slow increase)
- exponential phase (increase)
- stationary phase (plateau)
- death phase: decrease
- long term stationary phase- up and down
5
Q
what happens during the lag phase?
A
- cells synthesize new components, replicate DNA, divide
6
Q
What happens during the exponential phase?
A
- the rate of growth and division is constant and maximal, and cells grow as quickly as they can for conditions available (increase)
7
Q
What happens in the stationary phase?
A
- in a closed system, growth eventually seizes
- nutrient limitation, O2 availability, toxic waste accumulation
- total number of viable cells remains constant
8
Q
What happens during the death phase?
A
- # of viable cells declines exponentially, with cells dying at a constant rate
- nutrient deprivation and the build-up of toxic wastes cause irreparable harm to the cells (decrease)
9
Q
What is the long-term stationary phase?
A
- bacterial population continually evolves
- successive wave of genetic distinct variants
- natural selection occurs within the single culture
10
Q
growth rate calculations
k:
No:
Nt:
n:
g:
A
k: number of generations
No: initial pop number
Nt: population at the time
n: number of generations in time
g: generation time
11
Q
binary fission formula
A
Nt=No x 2^n
k = n/g
n = logNt - logNo
g = log2(T)
12
Q
What are the four environmental factors that influence growth?
A
- osmosis
- pH
- temperature
- oxygen concentration
13
Q
How do solutes affect osmosis and water activity?
what kind of environment does a microbe prefer?
A
- changes in osmotic concentrations in the environment might affect the cell
- hypotonic because they are protected by a cell wall that will prevent overexpansion of the plasma membrane
14
Q
What are two mechanisms that a microbe does to lower its solute concentration in the cytoplasm?
A
- MS (mechanosensitivity) channels in plasma membrane to allow solutes to leave
- protists use contractile vacuoles to expel excess water
15
Q
what salt concentration do halophiles and extreme halophiles prefer? what is salt in and salt out?
A
- H: 0.2 M, and E: 3-6.2 M
- salt in K and Cl in the cytoplasm; proteins need high salt levels
- salt out: blocks uptake
16
Q
what is pH?
What pH can acidophiles and alkaliphiles grow optimally in?
How can microorganisms respond to external pH changes?
A
- measures the acidity of the solution ( negative log of H ions in the concentration)
- Acid: 0-5.5 and Alk 8 -11.5
- by using mechanisms that maintain a neutral cytoplasmic pH
17
Q
why is regulating temperature an issue for microbes?
A
- they cannot regulate their internal temperature so they cannot build against heat like how pH and solutes can
- enzymes have optimal temperature
18
Q
how do proteins stabilize against temperature?
A
- more H-bonds, more proline (less flexible peptides) , chaperons (helps protein bind to its structure)
19
Q
how do membranes stabilize against temeprature?
A
- more saturated, more branched and higher molecular weight
- ether linkage and resistance to hydrolysis
20
Q
psychrophiles
A
0-20 C
21
Q
psychrotrophic
A
0-35
22
Q
mesophiles
A
20-45
23
Q
thermophiles
A
45-85
24
Q
hyperthermophiles
A
85-100
25
what are the five possible relationships that microbes have with oxygen concentration?
1. obligate aerobe
2. microaerophile
3. facultative anaerobe
4. aerotolerant anaerobe
5. strict anaerobe
26
What is an obligate aerobe? Where would the concentration be? Enzyme content of SOD, catalyze, and periodase?
- requires O2
- o2 is concentrated only at the top of the lid
(+SOD, + catalase, + peroxidase)
27
What is an microaerophile? Where would the concentration be? Enzyme content of SOD, catalyze, and periodase?
- requires low O2
- found slightly lower than obligated
(+SOD, +/- catalase, + peroxidase)
28
What is a facultative anaerobe? Where would the concentration be? Enzyme content of SOD, catalyze, and periodase?
- does not require oxygen but would grow better with it
- concentrated at the top with a gradient in the whole tube
(+SOD, + catalase, + peroxidase)
29
What is an aerotolerant anaerobe ? Where would the concentration be? Enzyme content of SOD, catalyze, and periodase?
- grow with or without o2
- particles scattered through the whole thing
(+SOD, + catalase, + peroxidase)
30
What is a strict anaerobe? Where would the concentration be? Enzyme content of SOD, catalyze, and periodase?
(+SOD, + catalase, + peroxidase)
- killed in the presence of o2
- concentrated only on the bottom
31
What are the three most reactive O2 species?
What are the three protective enzymes produced by aerobes?
- superoxide radical, hydroperoxide, and hydroxyl radical
- superoxide dismutase (SOD), catalase, peroxidase
32
What are other environmental issues that microbes deal with?
- pressure: microbes on land or water live at 1 atm
baratolerant/barophilic organisms change membrane lipids to adapt to higher pressures
- radiation
33
Three types of radiation that cause issues in microbes?
- Ionizing radiation: mutates and causes death
- UV: absorbed by DNA
- visible light = increases intenstities making it a stronger oxidizing agent
34
What are biofilms?
Communicates how?
- microorganisms that stick to the surface and make a protective layer
= communicates with each other by chemical signaling and sharing DNA
35
How do Biofilms form?
Problems they create?
- attach, produce a sticky substance to help group it, biofilms grow and get stronger, a piece can get broken off and spreads
- causes infections on medical devices
- contaminates water systems
- affects ship by increasing drag (slower)
36
What is quorum sensing?
What is needed for this to work?
What does it contribute to?
How does this work?
- bacteria communicate by small molecules that diffuse into the environment, but for this to happen, there need to be enough microbes present
- biofilm production
- AI (autoinducer) will synthesize and diffuse out of the cell (not enough to trigger anything)
- population increases till threshold
- extracellular AI concentrations increase as population increases and AI diffuses into cells
- Al binds to receptors triggers signaling networks that start a cooperative process
37
What are the common types of media components?
- Peptones—partial proteolytic digestion of protein sources
- Extracts—aqueous extracts that contain amino acids,
peptides, nucleotides, organic acids, vitamins, and minerals
- Usually beef or yeast
- Agar—sulfated polymer solidifying agent. Most
microorganisms cannot degrade it
38
Defined/minimal medium
Complex/rich media
Each ingredient is defined with a chemical formula
- some ingredients of non-specific chemical composition
39
Supportive media
Sustain the growth of many microorganisms
40
Enriched media
Supportive media supplemented with special nutrients
41
Selective media
allow the growth of some microbes, inhibits others
42
Differential media
- distinguish among different types of microbes based on their biological characteristics –
43
what is a pour plate and the purpose of doing one?
- samples are diluted and mixed in with liquid agar which is then poured into a sterile cultivated dish
- useful for sampling heterogeneous populations of microbes that might produce overgrown colonies or require different O2 levels
44
what is a spread plate and purpose?
- a small amount of the sample is placed in the center of a solidified medium and the spreader spreads the solution
- isolate individual colonies, count and experiment further
45
streak plate
spreads mixture of cells on an agar plate using an inoculation loop
- purpose is to get individual cells that are separated from each other
- each cell can reproduce to make a separate colony
46
how can growth be measured?
- standard plate count (CFU and dilution)
- counting chambers—special slides and cover slips
with grids to facilitate counting
- Membrane filter technique—microbes in liquid are
filtered, grown on a plate, then stained
- Flow cytometry—stream of cells so narrow that one
cell at a time passes through the laser beam
47
How is cell mass measured?
- dry weight- dehydrating culture and measuring it (time-consuming and not sensitive)
- concentration of a particular cell constituent: concentration of protein or nucleic acid proportional to the number of cells
- spectrophotometry: amount of light scattering directly proportion to cell biomass
48
What are two ways cultures can be continuous?
- batch culture
- chemostat: nutrients are consistent; u added, and waste is removed (keeps it in growth phase)
= the rate of new nutrients added = rate of waste removed
49
What are two ways that anaerobic microbes be cultivated?
- anerobic jar and anerobic chamber
= Both make sure microbes that cannot survive in O2 can be observed and studied safely
50
what are the three common microbial control methods?
1. physical agent
2. chemical agents
3. biological agents
51
sterilization
- all living cells, spores, and acellular entities are destroyed or removed from an object
52
disinfection
killing, inhibition, or removal of many (but not all) disease-causing microorganisms
53
sanitation
reduction of microbial population to levels deemed safe by public health standards
54
antisepsis
destruction of microbes on living tissue
55
antiseptic
chemical agents
56
chemotherapy
—a generic term that describes the application of chemicals to kill microorganisms
57
What is the impact of biocide exposure?
- as time increases, the number of microbes decrease
58
what are cidal vs static agents?
- cidal agents -- kill microorganisms directly
- static - stops the growth of microorganisms but does not kill them directly
59
decimal reduction time
D-value
Z-value `
Decimal reduction time = time required to kill 90% of (all) microorganisms
* D value = time required to drop population by 10-fold
* Z value = temperature change that decreases a microbial population by 90%
60
What is filtration? What are the types of filters?
- reduces the microbial population in heat-sensitive materials by removing microorganisms
- membrane filters, air filters and depth filter
61
what are three ways sterilization can be used?
- autoclave: increases atmospheric pressure and temperature to pump in hot steam (effective against all microorganisms)
- dry heat sterilization: less effective than moist heat (high temperatures and longer exposure time)
- pasteurization: controlling heart at a temperature well below boiling ( does not sterilize but does kill pathogens and slows spoilage by decreasing the number of organisms)
62
How can the two types of radiation be used for sterilization?
- UV: inducing thymine dimers (screws up the way chromosomes interact with things)
= limited to surface sterilization because it can't penetrate anything else
= used for water treatment
- ionizing radiation: introduces free radicals
= Gama radiation penetrates deep into objects (making chemically reactive free radicals)
= used for sterilization and pasteurization of antibiotics and hormones
63
what are chemical controlling agents?
- phenolics- denatures proteins and disrupt cell membranes (Like Lysol and is commonly used in labs and hospital disinfectants)
- alcohols - denature proteins and dissolve membrane lipids (widely used disinfectant) - 70% ethanol in bio lab
- halogens - oxidizing agent (iodine)
- heavy metals- inactive proteins ( mercury, silver copper etc)
- gases
64
Who was Paul Enrich?
- cure syphilis
- first specific chemotherapeutic agent for bacterial disease
65
gerhad domgak
- sulfa drug.- found that protonisl red was good for treating infections but made you red so it was later replaced by penicillin
66
sekann walksman
discovered streptomycin to fight against TB
67
How can antimicrobial drugs' effectiveness be measured?
- minimal inhibitory concentration (MIC) - lowest concentration of drugs that prevent the growth of the pathogen
- minimal lethal concentration (MLC)- the lowest concentration of drug that can kill the pathogen
68
what was the dilution susceptibility test? and war did it determine? (look at this later)
- used to determine MIC and MLC values
- took a media with different concentrations of the drug and ran it
= first run they found 0.25-1 tubes had growth but 2-16 did not show anything so they subculture it and placed them with new media
= the second run found that 2-4 had growth and 8-16 didn't
- the MIC was 2 since it had the lowest concentration and 8 was the MLC since it had the lowest concentration that could kill the drug
69
What were the disk diffusion tests?
Also known as?
What is a test similar to this one?
- disks that are infused with antibiotics are placed into a plate and measure the zone of inhibition
= Determine how sensitive or resistant bacteria and fungi are to different antimicrobial compounds
- also known as the Kirby-Bauer method
- Etest same thing but uses a gradient of antibiotics
70
what are the 4 basic sites of antibiotic activity?
inhibition of cell wall synthesis, ribosomes, nucleic acid synthesis, and metabolic antagonist
71
what drug is used to inhibit cell wall synthesis?
- penicillin
- B-lactam ring is important for bioactivity and will inhibit cell wall synthesis
72
How can penicillin inhibit cell wall synthesis?
- pencil in will intercept key enzymes that facilitate the reaction as the wall is being built
- t will bind and make the cell walls lose making it unprotected losing cohesion and dies
- Pensilin-resistant organisms make B-lactamase which hydrolyzes the bonds in the rings
73
What are three antibiotics that can inhibit cell wall synthesis?
- penicillin
- cephalosporins: structurally and functionally similar to penciling
- vancomycin: stops the cell wall synthesis by binding to the substrate instead of enzymes
74
where do the following inhibitors bind on the ribosomes and what effect does it have?
- macrolides
- aminoglycoside
- chloramphenicol
- tetracyclines
- macrolides bind near the 50S peptidyl transferase site, blocking elongation
- aminoglycosides - stops peptide elongation at 30S
- chloramphenicol - binds at 23S RNA and stops peptide formation
- tetracyclines- bins to 16s rRNA blocking tRNA codon binding
75
what are metabolic antagonists?
- sulfa drugs?
- trimethoprim?
- folic acid?
- drugs that stop bacteria from performing by blocking the function of metabolic pathways
= bacteriostatic and broad - stops bacteria from growing and not killing it right away (static)
= high therapeutic index - safe for people
- prevents the synthesis of DNA, RNA, proteins
- inhibits the same pathway as sulfa and structurally similar to folic acid
- important for building nucleic acids and ATG codons
= in the pathway there is an enzyme at each step and so the antagonist has the same homology to the substrate and will bind there, and so the sulfa drug will come in and block the advancement
76
what do inhibitors of nucleic acid stop?
why aren't the drugs toxic?
- DNA gyrase, topiosmerase and RNA polymers
- drugs arent as toxic as other antibiotics because bacteria and euk have similar nucleic acid synthesis pathways
77
intrinsic?
aquired?
persisters
- mycoplasm resistant to B-lactam and otehr cell wall inhibitors because there is no cell wall
- happens when there is a change in the genome of a bacteria that converts it to become resistant
- rides out exposure and goes into hibernation - it is a drug-tolerant bacteria (some do not have any mechanisms for AMR)
78
4 mechanisms for drug resistance
- modify target of antibiotics (mutate_
- drug inactivation
- bypass biochemical reaction inhibition by agents or increase production of target metabolite
- minimizes concentration of antibiotics in cell (efflux pump)
79
4 ways microbes have adapted to drugs
- random mutation
- recombination
- horizontal gene transfer
- continued drug therapy
