Exam 2- Growth

Question 1

What is culture medium?

Answer 1

nutrients prepared for microbial growth

Question 2

What does it mean to inoculate something?

Answer 2

to intentionally introduce microbes into medium

Question 3

What is a culture?

Answer 3

microbes growing in or on a medium

Question 4

What is a pure culture?

Answer 4

a genetically homogeneous population of microbes

Question 5

What does sterile mean?

Answer 5

no viable organisms in or on a medium or object (including endospores & viruses)

Question 6

What is a chemically defined media?

Answer 6

when the exact chemical composition is known

Question 7

What is a complex media?

Answer 7

when the exact composition is not known

Question 8

What is agar?

Answer 8

a complex polysaccharide that is commonly used to solidify media

Question 9

Why do we use agar?

Answer 9

1. nontoxic to most microbes
2. not metabolized by most microbes
3. stable in the autoclave
4. once solidified at 40C it remains sold over a wide range of temps.

Question 10

What is a colony?

Answer 10

a visible mass of cells arising from a single cell

Question 11

What is a colony often called?

Answer 11

a colony-forming unit (CFU)

Question 12

What is the streak plate method used for?

Answer 12

to isolate pure cultures

Question 13

What does selective media mean?

Answer 13

to suppress unwanted microbes & encourage desired microbes

Question 14

What is enrichment media?

Answer 14

used to increase numbers of desired organism to detectable levels

Question 15

What is differential media used for?

Answer 15

to expose biochemical differences between species that grow equally well

Question 16

What is in mannitol salt agar?

Answer 16

sodium chloride, D-Mannitol, & Phenol red

Question 17

Describe binary fission.

Answer 17

where one parent cell splits into two daughter cells

Question 18

What happens during exponential growth?

Answer 18

population size doubles at a fixed rate

Question 19

What generates an exponential curve?

Answer 19

plotting the increase in the number of cells over time

Question 20

How is growth plotted?

Answer 20

on a semi-log scale

Question 21

Why is exponential growth no indefinite?

Answer 21

because nutrient consumption & toxic by-products eventually slow the growth rate until is halts

Question 22

What happens when medium conditions deteriorate?

Answer 22

alterations occur in membrane composition, cell size, & metabolic pathways, all of which impact generation time

Question 23

Explain a batch culture.

Answer 23

a liquid medium within a closed system

Question 24

Explain a continuous culture.

Answer 24

an open system where fresh medium is continually added & spent medium removed

Question 25

What does a continuous culture support?

Answer 25

prolonged exponential growth

Question 26

Explain direct counts.

Answer 26

microorganisms can be counted directly by placing dilutions on a special microscope slide called a Petroff-Hausser counting chamber

Question 27

What is a viable bacterium capable of?

Answer 27

dividing & forming a colony on a solid medium

Question 28

When is counting bacteria by filtration used?

Answer 28

when quantities of bacteria are low

Question 29

What does turbidity mean?

Answer 29

cloudiness

Question 30

How can the number of cells be estimated?

Answer 30

by measuring the turbidity of a cell culture

Question 31

What factors can affect growth of microbes?

Answer 31

pH, temperature, pressure, & osmolarity

Question 32

What are extremophiles?

Answer 32

microbes that can grow in extreme environment

Question 33

What environments are considered extreme?

Answer 33

outside normal human habitats

Question 34

What are proteins & other macromolecular structures within the cell are affected by?

Answer 34

environmental change

Question 35

Why can't microbes control their temperature?

Answer 35

bacterial temperature matches temperature in the immediate environment

Question 36

What does temperature affect?

Answer 36

the rate of motion, membrane fluidity, nutrient transport, DNA/RNA stability, & enzyme structure & function

Question 37

Explain psychrophiles.

Answer 37

organisms capable of growth in cold temperatures (0-21C, optimum 14C)

Question 38

Explain mesophiles.

Answer 38

microorganisms capable of growth at moderate temperatures (15-45C, opt. 20-40C)

Question 39

Explain thermophiles.

Answer 39

heat-loving organisms (50-have 80C)

Question 40

Explain hyperthermophiles.

Answer 40

microorganisms capable of growth at very hot temperatures (65-121C)

Question 41

What happens to enzymes at high temperatures?

Answer 41

they can denature

Question 42

Describe Listeria monocytogenes.

Answer 42

listeriosis, gram-positive, non-spore-forming bacteria, can grow & divide at 4C, food-borne pathogen

Question 43

What do lyophilization mean?

Answer 43

freeze-drying- frozen & dehydrated in a vacuum

Question 44

What is water activity a measure of?

Answer 44

water availability

Question 45

What decreases water activity?

Answer 45

interactions with solutes

Question 46

What is osmolarity a measure of?

Answer 46

the number of solute molecules in a solution

Question 47

What are halophiles?

Answer 47

species that require high salt concentrations

Question 48

What salt concentrations do most bacteria prefer?

Answer 48

concentrations at 0.05-1M (0.2-5%)

Question 49

What pH do most bacteria grow?

Answer 49

between 6.5 & 7.5

Question 50

What can changes in pH alter?

Answer 50

protein structure

Question 51

Describe Helicobacter pylori.

Answer 51

ancient symbiont, gram negative, proteobacteria, urease positive

Question 52

What are aerobes?

Answer 52

use oxygen as terminal electron acceptor in the electron transport chain to extract energy trapped in nutrients

Question 53

What are reactive oxygen species?

Answer 53

oxygen molecules or ions with one too few or too many electrons

Question 54

What forms of oxygen are very reactive & toxic to cells?

Answer 54

Superoxide free radicals, Peroxide anion, Hydroxyl radical

Question 55

What are strict aerobes?

Answer 55

aerobes that grow only when oxygen is present & consume oxygen during metabolism

Question 56

What are strict anaerobes?

Answer 56

anaerobes that die in small amounts of oxygen, do not use oxygen as an electron acceptor, generally obtain oxygen atoms from water.

Question 57

Explain facultative anaerobes.

Answer 57

possess enzymes to detoxify oxygen radicals & also machinery for bother fermentation & aerobic respiration

Question 58

Discribe aerotolerant anaerobes.

Answer 58

use only fermentation to provide energy but contain superoxide dismutase & catalase or peroxidase to protect them from ROS

Question 59

Describe microaerophiles.

Answer 59

will grow only at lo oxygen concentrations, possess decreased level of superoxide dismutase &/or catalase

Question 60

Describe endospores.

Answer 60

highly differentiated cells resistant to heat, desiccation, harsh chemicals, radiation

Question 61

What does dormant mean?

Answer 61

not metabolically active

Question 62

What is germination generally triggered by?

Answer 62

heat & amino acids

Question 63

What can sporulation be triggered by?

Answer 63

starvation

Question 64

Explain spore structure.

Answer 64

makes the spore resistant to many environmental stresses that kill vegetative cells

Question 65

What is a biofilm?

Answer 65

a mass of bacteria that stick to & multiply on a solid surface

Question 66

What do microbes in a biofilm do?

Answer 66

share nutrients

Question 67

What does formation of a biofilm involve?

Answer 67

quorum sensing

Question 68

What is quorum sensing?

Answer 68

where bacteria measure population size through the sending & receiving of chemical signals.