exam 3

__ refers to an increase in cell number

growth

most bacteria increase their numbers through ____

binary fission

the double of a population is called a ____

generation

the ___ divides cells in binary fission

septum

what are Fts proteins? how do they grow?

• filamentous temperature sensitive mutants

• grow normally at low temperatures but fail to divide normally at high temperatures

how are Fts proteins identified

immunogold labeling techniques

divisome: function of FtsZ

forms the ring (tubulin like)

divisome: FtsK function

helps chromosomes segregate

divisome: MinE function

finds center of cell, recruits FtsZ and inhibits MinC

divisome: MinC function

prevent cell division until FtsZ finds the middle

___ precedes FtsZ ring formation

DNA replication

FtsZ rings ___ constricting the membrane at the center

depolymerizes

MreB function

forms polymers similar to the actin filaments that make up a cytoskeleton

• dictates cell shape

where does peptidoglycan grow from?

the FtsZ ring

function of autolysins

break glycosidic bonds in peptidoglycan at point of new synthesis (high regulated)

function of bactoprenol

highly hydrophobic molecule that shuttles precursors across the membrane

• interacts with assembly proteins to catalyze incorporation of new sugars (glycosidic bonds)

function of peptidoglycan transpeptidase

• catalyzes cross linking

• target of penicillin

what substances are directly involved with the synthesis of peptidoglycan

bactoprenol and transpeptidase

what is transpeptidation?

trading one peptide bond for another, crosslinking occurs in polysaccharide chains

____ is the time required for one generation to occur, which is ____ related to growth rate

generation time (g); inversely

____ is a pattern of growth which the population doubles per unit time

exponential growth

N = (N0)(2^n): explain each variable

N = number of cells at a given time

N0 = starting number of cells

n = number of generations

g = t/n: explain each variable

g = generation time

t = time

n = number of generations

formula for number of generations

n = 3.3 (logN - logN0)

describe lag phase (1) of the growth cycle

cells are getting used to new environment

describe exponential phase (2) of growth cycle

rapid growth, generation time stabilizes

describe stationary phase (3) of the growth cycle

nutrients begin getting used up, not much rapid growth

describe death phase (4) of growth cycle

no nutrient source left for the cells to grow

what are chemostats used for?

grow cells in exponential phase for a long period of time

what 3 things does using a chemostat allow for?

1. control of bacterial growth rate

2. control of cell density

3. extended exponential growth

what is it called when the dilution rate exceeds the maximum growth rate of the organism? (i.e. the medium is coming in too fast)

washout

do pure cultures have to be used in a chemostat?

no

benefits of using chemostats

• constant supply

• ecological studies

• enrichment

• measure genetic variations/mutations

• steady state cells are the best to work with in experiments

what are the two types of direct measurements of microbial growth

• total cell counts

• viable counts

what is the indirect measurement of microbial growth?

turbidometric methods

describe direct measurements

• count both viable and nonviable cells

• use a Petroff-Hauser chamber or spread/pour plate

• can be difficult to count motile cells

what dye can be used for differentiation between live and dead cells

methylene blue

what can be used to kill motile cells

CHCl3 (chloroform)

3 sources of error in plate counting

1. unsuitable culture conditions

2. procedural errors

3. cell clumping

____ is the cloudiness of media

turbidity

turbidity and viable cell count are ___ proportional

directly

why is a viable count more sensitive than a microscopic count?

it only counts live cells

what is the “great plate count anomaly”?

the drastic discrepancy between the high number of microbial cells observed under a microscope vs. what grows on plates

4 factors that affect microbial growth

1. temperature

2. pH

3. water availability

4. oxygen concentration

what are the ideal temperatures for the following:

psychrophile

psychrotolerant (mesophile)

thermophile

hyperthermophile

respectively:

0-20C

20-40C

45C+

80C+

enzymes that are active in the cold tend to have? (helices? side-chains? weak interactions? membrane lipids? cryoprotective?)

more alpha helices, less B sheets, more polar side chains, fewer weak interactions, more unsaturated lipids in the membrane, cryoprotective molecules reduce dehydration and ice-crystal formation

enzymes that are active in the heat tend to have? (substitutions? bonds? solutes? fatty acids? monolayers?)

AA substitutions to increase stability at high temperatures, more ionic bonds and denser hydrophobic protein cores, cytoplasmic solutions to stabilize, high saturation of fatty acids in membranes, use of lipid monolayers in archaea

___ like low pH. ___ is an example

acidophiles; Pircrophilus oshimae

• optimum pH is 0.7 and lyses when pH >4

____ like high pH. ____ is an example

alkaliphiles; Bacillus firmus

• optimum is 11

• uses the Na+ gradient to drive transport and locomotion

____ is the water available for a microbe to grow

water activity

____ are solutes that draw in water to help maintain a positive water balance. used by ____

compatible solutes; halophiles

examples of compatible solutes

1. amino acid (glycine betaine)

2. carbohydrate (sucrose)

3. alcohol (glycerol)

____ require O2 for growth; use it as final electron acceptor

obligate aerobes

____ do not need or use O2 as a nutrient - it is toxic

obligate (strict) anaerobes

____ are organisms that can switch between aerobic and anaerobic. they prefer ___

facultative an/aerobes; aerobic

____ require some oxygen, but atmospheric levels are toxic

microaerophiles

_____ are bacteria that are exclusively anaerobic, but are insensitive to presence of O2

aerotolerant anaerobes

toxic forms of oxygen and their formulas

superoxide (O2-), hydrogen peroxide (H2O2), hydroxyl radical (OH•)

enzymes that destroy toxic oxygen

catalase, peroxidase, superoxide dismutase, superoxide reductase

a positive catalase test will show ____

oxygen bubbles

2 types of physical means for antimicrobial control involving heat

1. heat sterilization - eliminate most heat resistant organisms (endospores), can use autoclave

2. pasteurization - reduces microbial load, less damaging to food

an ____ permits applications of steam heat under pressure at temperatures above the boiling point of water, killing endospores

autoclave

temperatures for flash vs. bulk Pasteurization

respectively:

71C for 15 seconds

65C for 30 minutes

why is heat an effective sterilizing agent?

comprises cell membranes and proteins

2 types of physical means for antimicrobial control involving radiation

1. UV radiation: causes DNA damage, used for surface decontamination

2. ionizing radiation: damage through generation of highly reactive ions; the lethal dose used to kill organisms is sufficient to reduce population by a factor of 10^-12

2 types of physical means for antimicrobial control involving filtering

1. depth filters: fibrous nature; used to pre-filter liquids; used for sterilization of air

2. membrane filters: standard (traps filtrate of surface, common) or nucleopore (formed by etching polycarbonate film after nuclear radiation)

____ is the dose of radiation required to kill 90% of a microbial population

decimal reduction dose

_____ agents kill bacteria

bacteriocidal

_____ agents prevent growth but do not kill

bacteriostatic

____ agents kill and lyse the cell

bacteriolytic

_____ is the lowest concentration of antimicrobial that inhibits growth completely

minimum inhibitory concentration

____ is a technique used to measure the susceptibility of bacteria to different antibiotics

disc-diffusion technique

____ is the circular area around the spot of antibiotic in which bacteria colonies do not grow

zone of inhibition

____ are gaseous infusion of chemicals used for the sterilization of heat sensitive materials. _____ is an example

sterilants; formaldehyde

____ kill most organisms, but not endospores. ____ is an example

cationic detergents

____ reduce microbial populations to “safe” levels. an example is weak solutions of ____ compounds

sanitizers; chlorine or iodine

____ are antimicrobial agents that are safe for application to living skin. ___ are an example

antiseptics; alcohol solutions

2 types of antimicrobial agents used in vivo

1. synthetic

2. antibiotics

what are the two major types of synthetic antimicrobial agents

1. growth factor analogs such as sulfa drugs, isoniazid, nucleic acid analogs

2. quinolones that are DNA gyrase inhibitors

what are the two major types of antibiotic antimicrobial agents

1. natural - produced by fungi and bacteria

   1. semisynthetic - increased efficacy

____ is the range of species for which an antibiotic is effective

antibiotic spectrum

____ is when the effect of a combination of antibiotics is greater than the sum of either antibiotic separately

antibiotic synergism

____ is the interference of the efficacy of one antibiotic when coupled with a second antibiotic

antibiotic antagonism

_____ mimic the structure of a growth factor to stop a growth process

growth factor analogs

____ inhibit folic acid syntheis

sulfa drugs

2 examples of quinolines

nalidixic acid, ciprofloxin

____ is crucial to folic acid synthesis

p-aminobenzoic acid

_____ is the analog to p-aminobenzoic acid

sulfanilamide

_____ blocks folic acid synthesis by mimicking _____

sulfanilamide; p-aminobenzoic

____ is an enzyme that breaks down the ____ ring of penicillin

B-lactamase; B-lactam

to avoid resistance by bacteria, _____ penicillin have been made because it’s normally produced ____

semisynthetic; naturally

what are 3 substances that have been modified to resist B-lactamase activity

ampicilin, oxacilin, methicilin

mechanisms of resistance: _____ is the target of binding antimicrobial mutates and cannot bind. ____ is an example

target modification; B-subunit of RNA polymerase (rifampicin)

mechanisms of resistance: ____ is when the bacterial cell cannot antimicrobial so it doesn’t work. ____ is an example

antibiotic efflux; tetracycline efflux of enteric bacteria

mechanisms of resistance: ____ is when the antibiotic is modified by the bacteria. ____ is an example

antibiotic modification; B-lactamase (penicillinase)

____ is when the pathway is interrupted by antimicrobial so it used a different pathway to avoid it. ____ is an example

resistant pathways; circumvention of folic acid synthesis - sulfonamides

____ is when the cell has a protective coat and antimicrobial cannot reach the target. ____ is an example

antibiotic impermeability; penicillan in P. aeruginosa

how do the b-lactam antibiotics function

prevent cell well cross linking

what advantages do the cephalosporins have as compared to the penicillins for treating infections due to gram-negative bacteria?

increase resistance to B-lactamase

____ are genetic elements with an obligate ____ replication cycle (needs a host to replicate

viruses; intrecellular