Bacterial Growth

Question 1

how is microbial growth measured?

Answer 1

generation time- time it takes microbes to double

Question 2

how do microbes reproduce?

Answer 2

binary fission

Question 3

mycobacteria v e coli doubling time

Answer 3

20 hours v 20 minutes

Question 4

what limits bacterial growth?

Answer 4

nutrient supplies/ key resources

accumulation of toxic metabolic products

antibiotics from neighboring micorbes

immune system

Question 5

lag phase vs log phase vs stationary phase

Answer 5

lag phase- beginning where culture does not grow exponentially

log phase- exponential culture growth

stationary phase- end where culture does not grow

Question 6

lag phase

Answer 6

occurs when bacteria encounter new environment

length depends on kind of bacteria, inoculum source, and nature of new medium

Question 7

log phase

Answer 7

exponential growth

depends on type of organism, nature of medium, temperature

sensitive to antibiotics during this phase

Question 8

stationary phase

Answer 8

growth slows for various reasons (pH change, decrease in oxygen)

increased resistance to antibiotics

Question 9

death phase

Answer 9

rate of death surpasses rate of growth

can be caused by pH change

can occur after stationary phase

cell morphology can change during death phase

Question 10

what must happen for a bacterium to grow

Answer 10

need to generate cell membrane, proteins, flagellum, chromosomes, cell wall

need carbon nitrogen and phosphorus

Question 11

bacterial carbon sources

Answer 11

glucose, other sugars, amino acids

some bacteria can use lipids, organic acids, alcohols, polymers

Question 12

how do bacteria absorb proteins

Answer 12

use proteases to chop up peptides and create amino acids that can be absorbed

often these proteases are virulance factors

Question 13

extracellular nucleases

Answer 13

allows bacteria to absorb C, N, and P from host DNA

Question 14

bacteria can use phospholipases to acquire C, N and P from host. using phospholipase to lyse a cell yields iron

Answer 14

ok

Question 15

how is iron important in pathogenesis

Answer 15

iron is needed for ATP generation, and is conserved by the host to make less available to pathogens

ability to scavange iron is key to virulence

Question 16

siderophores

Answer 16

high affinity for iron

make iron available to bacteria by stealing iron from host and have receptors to re-enter bacteria

Question 17

how else can bacteria get iron besides siderophores

Answer 17

lyse open an iron rich cell

Question 18

what are growth factors?

Answer 18

presynthesized factors that the bacteria need to grow but cannot synthesize themselves

Question 19

fastidious microbes

Answer 19

require purines, pyrimidines, vitamins, amino acids to grow

Question 20

prototropic microbes

Answer 20

synthesize almost everything they need to grow

Question 21

requirement for growth factors can be diagnostic

Answer 21

ok

Question 22

physical requirements for microbial growth

Answer 22

optimal temperature

optimal pH

high salt and sugar concentrations inhibit growth

Question 23

turbidity

Answer 23

visual detectoin of bacteria

faint turbidity can still contain up to 1 million bacteria per ml

milky or very turbid cultures have close to a billion bacteria per ml

Question 24

direct counts via microscopy

Answer 24

put on a slide and manually counted

still require 100,000 bacteria/ mL

Question 25

what is an advantage of viable counts vs microscopy?

Answer 25

plate counts let you know how many live cells are in a sample, and measured as colony forming units

Question 26

glyoxalate shunt

Answer 26

unique to microbes

2 enzymes (isocitrate lyase and malate synthase) shunt from isocitrate to malate in TCA

happens w/ a lot of acetyl-CoA (when cells are using lipids as a primary resource)

Question 27

how is the electron acceptor different in microbes

Answer 27

we can only use oxygen

bacteria can use many different final acceptors (nitrogen, iron, sulfur, etc)

Question 28

what can the proton gradient be used for in microbes?

Answer 28

ATP genetation

flagella motility

drug resistance (use gradient to create efflux)

Question 29

what happens when ETC is unavailable?

Answer 29

fermentation- allows for regeneration of NAD and generation of ATP

generates less energy than respiration

Question 30

lactic acid fermentation

Answer 30

pyruvate reduced by lactate dehydrogenase, regenerating NAD and lactate

Question 31

fermentation to butyric acid

Answer 31

fermentation from pyruvate to butyric acid in gut, causes smell of feces and vomit

Question 32

propioinic acid fermentation

Answer 32

associated w/ acne

Question 33

yeast fermentation

Answer 33

pyruvate reduced to acetaldehyde, which is reduced by alcohol dehydrogenase to ethanol

Question 34

differential acid production can show that different bacteria eat different things

Answer 34

different bacteria use different food sources and this info can be diagnostic

Question 35

define: obligate aerobes

Answer 35

need O2, no alternative e receptors, no fermentation

Question 36

facultative anaerobes

Answer 36

growth occurs w/ or w/o oxygen

Question 37

aerobes and facultative anaerobes can detoxify reactice oxygen species

Answer 37

catalase (breaks down H2O2) and superoxide (breaks down superoxide, free radical oxygen) dismutase

Question 38

obligate anerobes

Answer 38

cannot surivive w/ oxygen

cannot detoxify ROS

Question 39

aerotolerant anaerobes

Answer 39

can tolerant oxygen, but do not use it for respiration

can survive ROS

Question 40

micoaerophiles

Answer 40

require low concentrations of oxygen (5%)

environments found in the gut