4. Microbial Nutrition, Measuring Microbial Growth

Question 1

2 reasons why knowing growth requirements for microbes is important

Answer 1

1. To control microbial growth

2. To be able to culture microbe

Question 2

2 ways microbes can get iron?

Answer 2

Secrete siderophores

Secrete hemolysins (lyse RBCs)

Question 3

What are siderophores? How does it work?

Answer 3

Low MW molecules that are able to complex with ferric iron and supply it to the cell

Ferric iron in middle of 3 siderophores => bind to siderophore receptor

Question 4

Once iron has entered a G- bacterium, how can it get into the cytoplasm?

Answer 4

When iron reaches periplasmic space, moves through PM with aid of a TRANSPORTER

Reduced to ferrous form (Fe2+) afterwards

Question 5

What are growth factors? 3 examples?

Answer 5

Pre-formed organic nutrients

Amino acids, vitamins, nucleic acids

Question 6

3 types of nutrition microbes need to acquire?

Answer 6

Energy, electrons, carbon

Question 7

What are the 5 major nutritional types of microorganisms?

Answer 7

Photo-litho-autotrophy

Photo-organo-heterotrophy

Chemo-litho-autotrophy

Chemo-litho-heterotrophy

Chemo-organo-heterotrophy

Question 8

2 types of energy source trophs

Answer 8

phototroph, chemotroph

Question 9

2 types of electron source trophs

Answer 9

organotroph, lithotroph

Question 10

2 types of carbon source trophs

Answer 10

heterotroph, autotroph

Question 11

Do lithotrophs oxidize or reduce electron donors?

Answer 11

Oxidize them

Question 12

What is auxotrophy?

Answer 12

Inability to synthesize particular organic compound required for growth

Question 13

3 major processes of nutrient uptake?

Answer 13

Simple diffusion

Active transport

Facilitated diffusion

Question 14

2 general types of growth media and their differences?

Answer 14

Complex and synthetic

Complex = undefined

Synthetic = defined

Question 15

Composition of the 2 types of growth media?

Answer 15

Complex - protein hydrolysate (beef/soy protein), water soluble extract of yeast/beef, separate carbon source(glucose)

Synthetic - only specific amounts of known nutrients

Question 16

Differences between differential and selective media? Examples?

Answer 16

Differential allows one to distinguish among groups of microbes (blood agar)

Selective favors the growth of a particular type of microbe (eosin methylene blue)

Question 17

Word for the progeny that arise from a single cell?

Answer 17

Clonal

Question 18

Species vs strain?

Answer 18

Species - arbitrarily define group of orgs that with high degree of shared characteristics

Strain - isolate; arises from single cell

Question 19

What is a type strain?

Answer 19

Often one of the first isolates of a species and therefore the best chaacterized.. but not necessarily the most common

Question 20

4 phases of a bacterial growth curve?

Answer 20

Lag, exponential (log), stationary, death

Question 21

What is the variable you can determine from a growth curve?

Answer 21

‘g’ (growth) = time it takes for the pop. to double, but ONLY for the exponential phase

Question 22

What occurs during the stationary phase of a growth curve?

Answer 22

No net change in live biomass (growth/death still occurring)

Growth decrease due to limited nutrients/toxic build-up

Question 23

We can ONLY calculate ‘g’ during the ____________ phase

Answer 23

exponential (log)

Question 24

Microbe growth curve is a ______-____ plot

Answer 24

semi-log

Question 25

2 conditions of a closed system?

Answer 25

No nutrients added, no waste products removed

Question 26

Macronutrients for microbes? At what unit of concentrations? Important for what molecules?

Answer 26

C,H,O,N,S,P + K+/Ca2+/Fe3+

mg/L

Cellular macromolecules (carbs, lipids, proteins, nucleic acids)

For enzymes

Question 27

Why is iron in the environment limiting?

Answer 27

Oxidized to insoluble hydroxides = free iron is VERY low

Question 28

6 microbial micronutrients?

Answer 28

Ni+, Co2+, Cu2+, Zn2+, Mn2+, Mo2+

Question 29

Micronutrients are needed for enzymatic activity that require bounds metals at ______ concentrations

Answer 29

ug/L

Question 30

Source of micronutrients in nature? In lab?

Answer 30

Water leaching from minerals

Glassware, water, media

Question 31

What does ‘g’ stand for? What does ‘k’ stand for?

Answer 31

g = growth (time it takes for pop to double, ONLY for exponential phase)

k = mean growth rate