Microbial Growth

Question 1

Macronutrients

Answer 1

required in large amounts- C,N,H,O,P,S,K,Mg,Ca,Na

Question 2

Micronutrients

Answer 2

required in trace amounts

Fe, trace metals

Question 3

Growth factors

Answer 3

vitamins, AA, organic molecules the organism cant synthesize itself

Question 4

Reproduction

Answer 4

Binary fission: the cell grows in size until it forms a partition, septum, that constricts the cells into two daughter cells
clones, one copy of chromosome, sufficient ribosomes etc.
Steps: cell elongation, septum formation, formation of walls/cell separation

Question 5

growth of population

Answer 5

increase in the number of cells or biomass

Question 6

Requirements for cell division

Answer 6

*synthesis of new cell wall material
destruction by *autolysins
Bactoprenol allows peptidoglycan subunit to be exported across cytoplasmic membrane

Question 7

*Bactoprenol

Answer 7

allows peptidoglycan subunit to be exported across cytoplasmic membrane

Question 8

wall bands

Answer 8

scar between old and new peptidoglycan

Question 9

autolysins

Answer 9

create some gaps in peptidoglycan allowing rearrangement of the peptidoglycan and synthesis of a new cell wall

Question 10

MacConkey

Answer 10

selective medium
gram - grow
bile salts - NO gram +
Lactose fermenters: pink
lactose non-fermenters: colorless

Question 11

Mannitol-salt

Answer 11

selective medium
high NaCl: inhibits most gram- and many gram +
mannitol fermenters: yellow
non mannitol fermenters: pink

Question 12

why count bacteria

Answer 12

evaluate contamination of food or water
efficiency of antimicrobial agents
study microbial populations from different ecosystems

Question 13

Serial dilution

Answer 13

used to count the amount of bacterial cultures

Question 14

enumerating bacteria

Answer 14

viable counts: reliable - 30-300 colonies

Question 15

microscopic counts (define pros and cons)

Answer 15

counting chamber with a square grid.
count all cells: dead, alive, and cells that cannot be grown in lab
pros: fast no need to wait until bacteria has grown
cons: small cells can be missed, motile cells are hard to count and must be immobilized

Question 16

Flow cytometry

Answer 16

cells pass through in single file. Flourescent dyes in stained cells are detected. - can label specific cell type/species.
Used to sort cells according to size, shape, labeling etc
Example: test for which cells are dead or alive

Question 17

Turbidimetric method

Answer 17

Light is passed through a prism and filter into a sample containing cells, which scatter the light and a photocell measures the unscattered light.
Measures both living and dead cells, affected by properties of cells: size, clumping

Question 18

*Generation time

Answer 18

time needed for the population to double
Depends on: growth medium, conditions
When the conditions are right, microorganisms can grow exponentially. The population doubles at a constant rate

Question 19

Population growth and Generation time formula

Answer 19

N = N02^n
N = number of cells
N0 = initial number of cells
n = generation number

g = t/n
t = time

Question 20

Growth phases

Answer 20

lag phase
exponential phase
stationary phase
death phase

Question 21

lag phase

Answer 21

time needed by the bacteria to adjust to the new conditions, slow growth

Question 22

exponential phase

Answer 22

doubling of the population at a constant rate

Question 23

stationary phase

Answer 23

limiting nutriens are depleted or accumulation of a waste product that inhibits growth. Growth has stopped.
No net increase in cell number

Question 24

death phase

Answer 24

cells start to die, metabolism has stopped, cell lysis may occur - also exponential

Question 25

continuous culture

Answer 25

over time, most environmental systems can reach an equilibrium: cell division = cell death

Question 26

*chemostat

Answer 26

fresh medium: supply of limiting nutrients
overflow: death of microorganism
Used to keep the microorganisms in a constant growth rate over a long period of time
Parameters: concentration of a limiting nutrient, dilution rate - addition of fresh medium
** once equilibrium is reached, number of cells is constant. The growth rate equals the death rate (*washout)

Question 27

factors that affect growth

Answer 27

nutrients
temp
pH
osmolarity
oxygen
pressure
radiation

Question 28

**extremophiles

Answer 28

microorganisms that prefer extreme conditions

Question 29

**Psychrotolerant

Answer 29

organisms that can grow at 0C, but have optima around 20-40C

Question 30

**Barophilic (piezophilic)

Answer 30

grow best at high pressure

Question 31

Temperature of a hydrothermal vent??

Answer 31

350C

they have high temp and high pressure

Question 32

*halophile

Answer 32

microorganisms that can grow at high salt concentrations

Question 33

aerotolerant anaerobes

Answer 33

can grow in presence of oxygen but do not use it

Question 34

obligate anaerobes

Answer 34

inhibited or killed by oxygen