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microbio > lecture 5 and 6 > Flashcards

lecture 5 and 6 Flashcards

microbial growth

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)
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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
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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
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4
Q

what are the five phases of a microbial growth curve?

A
  1. Lag phase- cells are starting to adopt to change so there is no increase in cell count and cell starts yo prepare for making new components
  2. exponential phase -grows and divides a lot b/c there is no competition
  3. stationary phase - growth stops because conditions are not favorable (plateau)
  4. death phase: build-up of waste that kills cell, and exponential decrease of living cells
  5. long term stationary phase - bacteria population evolves by natural selection (so random growth peaks)
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5
Q

growth rate calculations
k:
No:
Nt:
n:
g:
binary fission formula
population doubles
growth rate constant
growth rate when the population doubles

A

k: number of generations
No: initial pop number
Nt: population at the time
n: number of generations in time
g: generation time

Nt=No x 2^n
Nt= 2No
k=n/g
k=1/g

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6
Q

what are the four environmental factors that can influence growth?

A
  1. osmosis
  2. pH
  3. temperature
  4. oxygen concentration
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7
Q

what kind of environments do microbes prefer?
how can microbes lower concentration in their cytoplasm?

A
  • hypotonic environments since they are protected to prevent overexpansion
    1. MS (mechanosensitivity) channels in plasma membrane to allow solutes to leave
    2. protists use contractile vacuoles to expel excess water
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8
Q

what are osmophiles?
the concentration of salt in halophiles and extreme halophiles?
what is salt in and out mean?

A
  • microgramins that can grow in environments with high osmotic pressure
  • 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
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9
Q

what is pH?
what pH can acidophiles and alkaliphilies 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
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10
Q

why is temperature an issue for microbes?
what do enzymes not have?

A
  • cannot regulate their internal temperature so they cannot build against disrupted heat like how solutes and pH can
  • no optimal temperature
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11
Q

how are proteins and membranes stabilized by?

A
  • proteins
    more H-bonds, more proline (less flexible peptides) , chaperons (helps protein bind to its structure)
  • membrane
    more saturated, more branched and higher molecular weight
    ether linkage and resistance to hydrolysis
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12
Q

what are the temperatures the following can survive in?

psychrophiles
psychrotrophic
mesophiles
thermophiles
hyperthermophiles

A

0-20
0-35
20-45
45-85
85-100

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13
Q

what are the five relationships that microbes can have with oxygen concentration?
describe where the concentration would be in a tube
enzyme content of SOD, catalyze, and periodase

A
  • obligated aerobe: requires O2 (has all three)
    o2 is concentrated only at the top of the lid
  • microaerophile: requires low O2 ( +. +/-, +)
    found slightly lower than obligated
  • facultative anaerobe: does not require oxygen but would grow better with it ( + + +)
    concentrated at the top with a gradient in the whole tube
  • aerotolerant anaerobe: grow with or without o2 ( + - +)
    particles scattered through the whole thing
  • strict anaerobe: killed in the presence of o2 ( - - - )
    concentrated only on the bottom
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14
Q

what are the three most reactive O2 species?
what are the three protective enzymes produced by aerobes?

A
  • superoxide radical, hydroperoxide, and hydroxyl radical
  • superoxide dismutase (SOD), catalase, peroxidase
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15
Q

what are the other challenges that microbes have to deal with?

A
  • pressure: microbes on land or water live at 1 atm
    baratolerant/barophilic organisms change membrane lipid to adapt to higher pressures
  • radiation:
    = Ionizing radiation: mutates and causes death
    = UV: absorbed by DNA
    = visible light = increases intstenties making it a stronger oxidizing agent
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16
Q

what are biofilms?
communincates how?

A
  • microorganisms that stick to the surface and make a protective layer
    = communicates with each other by chemical signaling and sharing DNA
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17
Q

how do Biofilms form?
problems they create?

A
  • attach , produce a sticky substance to help group it together, biofilms grow and gets stringer, a piece can get broken off and spreads
  • causes infections on medical devices
  • contaminates water systems
  • affects ship by increasing drag (slower)
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18
Q

what is quorum sensing?
what is needed for this to work?
what does it contribute to?
how does this work?

A
  • bacteria communicate by a small molecules that diffuses 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 difuses into cells
  • Al binds to receptors, triggers isgnialing networks that start a cooperative process
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19
Q

what are the coomon types of media components?

A
  • 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
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20
Q

Defined/minimal medium
Complex/rich media

A

Each ingredient defined with a chemical formula
- some ingredients of non-specific chemical composition

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21
Q

Supportive media
Enriched media
Selective media
Differential media

A
  • Supportive media - Sustain the growth of many microorganisms
  • Enriched media - Supportive media supplemented with special nutrients
  • Selective media—allow the growth of some microbes, inhibits others
  • Differential media—distinguish among different types of microbes based on
    their biological characteristics –
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22
Q

what is a pour plate and the purpose of doing one?

A
  • 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
23
Q

what is a spread plate and purpose?

A
  • 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
24
Q

streak plate

A

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

25
Q

how can growth be measured?

A
  • changes in cell number or mass
  • direct count:
    = 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
26
Q

how is cell mass measured?

A
  • 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
27
Q

how can cell growth be maintained at an exponential rate for a long time?

A
  • 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
28
Q

what are the two methods for anaerobic cultivation?

A
  • anerobic jar and anerobic chamber
    = Both make sure microbes that cannot survive in O2 can be observed and studied safely
29
Q

what are the three common microbial control methods?

A
  • physical agent = filtration (ait - sterilizes), heat (pressurized steam - sterilizes), and radiation (non-ionizing - UV col plasma - disinfection)
  • chemical agents - gas and liquids ( antispectic - antisepsis)
  • biological agents - predator and virus (antisepsis) and toxin (sterilization)
30
Q

sterilization

A

—all living cells, spores, and acellular entities are destroyed or removed from an object

31
Q

disinfection

A

killing, inhibition, or removal of many (but not all) disease-causing microorganisms

32
Q

sanitation

A

reduction of microbial population to levels deemed safe by public health standards

33
Q

antisepsis

A

destruction of microbes on living tissue

34
Q

antiseptic

A

chemical agents

35
Q

chemotherapy

A

—a generic term that describes the application of chemicals to kill microorganisms

36
Q

what impact does biocide exposure have?

cidal vs static agents

A
  • as time increases the number of microorganisms decrease
  • cidal agents – kill microorganisms directly
  • static - stops the growth of microorganisms but does not kill them directly
37
Q

decimal reduction time
D-value
Z-value `

A

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%

38
Q

what are filtration and the three types?

A
  • reduces the microbial population in heat-sensitive materials by removing microorganisms
  • membrane filters, air filter,s and depth filter
39
Q

what are three ways sterilization can be used?

A
  • autoclave: increases atmospheric pressure and temperature to pump in hot steam (effective against all microorganisms)
  • dry heat sterilization: less effective than moist hear (high temperatures and longer exposure time)
  • pasteurization : controlling hear at a temperature well below boiling ( does not sterilize but does kill pathogens and slows spoilage by decreasing the amount of organisms)
40
Q

how are the two types of radiation used for sterilization?

A
  • 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
41
Q

what are chemical controlling agents?

A
  • phenolics- denatures proteins and disrupt cell membranes (Like Lysol and is commonly used in labs and hospital disinfectants)
  • alcohols - denature proteins and disolve membrane lipids (widely used disinfectant) - 70% ethanol in bio lab
  • halogens - oxidizing agent (iodine)
  • heavy metals- inactive porteins ( mercury silver copper etc)
  • gases
42
Q

who discovered an antibiotic cure for syphilis?

A
  • paul enrich
  • first specific chemotherapeutic agent for bacterial disease
43
Q

gerhad domgak
sekann walksman

A
  • sulfa drug.- found that protonisl red was good for treating infections but made you red so it was later replaced by penicillin
  • discovered streptomycin to fight against TB
44
Q

What are the two concentrations of drugs that can impact pathogen growth?

A
  • 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
45
Q

what was the dilution susceptibility test? and war did it determine?

A
  • 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
46
Q

what were the disk diffusion tests?
also known as ?
what is a similar test like this one?

A
  • 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
47
Q

what are the four basic sites of antibiotic activity?

A

inhibition of: cell wall synthesis, ribosomes, nucleic acid synthesis, and metabolic antagonist

48
Q

what is the B-lactam ring?
what effect does penicillin have?
what do pencilin-resistant organisms make?
what are two antibiotics that can inhibit cell wall synthesis?

A
  • is important for bioactivity, it will inhibit transpeptidation by blocking cell wall formation by lysis
  • penciling fucks it up by intercepting key enzymes that facilitate the reaction as the cell wall is being built
    = It 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
  • cephalosporins: structurally and functionally similar to penciling
  • vancomycin: stops the cell wall synthesis by binding to the substrate instead of enzymes
49
Q

where do the following inhibitors bind on the ribosomes and what effect does it have?
- macrolides
- aminoglycoside
- chloramphenicol
- tetracyclines

A
  • 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
50
Q

what are metabolic antagonists?
- sulfa drugs?
- trimethoprim?
- folic acid?

A
  • 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
51
Q

what do inhibitors of nucleic acid stop?
why aren’t the drugs toxic?

A
  • DNA gyrase, topiosmerase and RNA polymers
  • drugs arent as toxic as other antibiotics because bacteria and euk have similar nucleic acid synthesis pathways
52
Q

intrinsic?
aquired?
persisters

A
  • 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)
53
Q

4 mechanisms for drug resistance

A
  • 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)
54
Q

4 ways microbes have adapted to drugs

A
  • random mutation
  • recombination
  • horizontal gene transfer
  • continued drug therapy

microbio (5 decks)

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