Microbial Nutrition and Growth

Question 1

What is carbon used for in organisms?

Answer 1

everything?

Question 2

What is quorum sensing?

Answer 2

bacteria communicate with each other by secreting molecules. signals can lead to new genes being expressed.

Question 3

Carbon source for photoautotrophs

Answer 3

CO2

Question 4

What are superoxide free radicals?

Answer 4

an oxygen-based free radical

Question 5

Which type of organisms are most likely to contaminate a brine (salt) solution found in pickles?

Answer 5

halophiles

Question 6

Describe plate counts

Answer 6

count colonies on plate, colonies between 25-250

Question 7

describe most probable number

Answer 7

best guess at cell number based on the fact that more dilutions are required for a denser culture. used for organisms that don’t grow well in solid media. Use different dilutions and dye indicators

Question 8

lag phase

Answer 8

cells not actively dividing, adjusting to environment

Question 9

What ingredient is added to make liquid media solid or semi-solid?

Answer 9

agar

Question 10

Describe two methods for obtaining isolated colonies.

Answer 10

streak plates and pour plate

Question 11

Describe binary fission. Describe how to calculate the number of cells after each round.

Answer 11

binary fission is the splitting of a bacterial cell. They split into two every time.

Question 12

Define facultative anaerobes, where they are in the tube, and a species example

Answer 12

prefer O2 but can adapt to a lack of it
E.coli

Question 13

define microaerophiles, where they are in the tube, and an example

Answer 13

prefer a low oxygen environment
campylobacter jejuni

Question 14

What macromolecules require nitrogen?

Answer 14

amino acids, DNA, RNA, and proteins

Question 15

Energy source for chemotrophs

Answer 15

organic and inorganic chemicals

Question 16

What is a colony?

Answer 16

cluster of cells that can be seen with the naked eye and originated from 1 cell

Question 17

Carbon source for chemoheterotrophs

Answer 17

organic chemicals

Question 18

describe direct microscopic count

Answer 18

individual cells are counted using a special cell counter and adding a known volume of the inoculum

Question 19

describe metabolic activity indirect measurement

Answer 19

production of a product or utilization of a substrate used to estimate cell number

Question 20

define obligate anaerobes, where they are in the tube, and example

Answer 20

cannot live in the presence of O2
clostridium

Question 21

Define obligate aerobes

Answer 21

need O2 to live

Question 22

stationary phase

Answer 22

no net growth, # of cells dividing and dying are at equal rates

Question 23

Which type of organisms are most likely to contaminate and grow in the refrigerator?

Answer 23

psychrotolerant

Question 24

define capnophiles

Answer 24

thrive in a high level of CO2

Question 25

What reaction does catalase catalyze?

Answer 25

coverts hydrogen peroxide into H2O and O2

Question 26

Carbon source for chemoautotrophs

Answer 26

inorganic molecules, fix their own C

Question 27

During which phase are bacteria most susceptible to antibacterial agents?

Answer 27

log phase

Question 28

What temperature do pathogenic organisms grow best at?

Answer 28

37 C

Question 29

describe dry weight measurment

Answer 29

used fo molds. cells are collected, dried, and then weighed

Question 30

Define generation time.

Answer 30

time to split into 2 cells

Question 31

Describe the range of temperature of growth for the following organism types: a. thermophiles (including extreme) b. mesophiles c. psychrotolerants (psychrotrophs) d. psychrophiles

Answer 31

a. thermophiles (including extreme)- 45-105 C b. mesophiles- 15-45 C c. psychrotolerants (psychrotrophs)- 0-40 C d. psychrophiles- -5-20 C

Question 32

What three enzymes are important for neutralizing superoxide free radicals? How do they function?

Answer 32

SOD- conversion of superoxide free radical and free H+ ions into hydrogen peroxide and oxygen catalase- converts hydrogen peroxide to H2O+O2 peroxidase- converts hydrogen peroxide and H+ ions into H2O

Question 33

describe turbidity (spectrophotometry/nephelometry)

Answer 33

cloudiness of the suspension is used to approximate the number of cells. Light is shone through the mixture and the percentage of light leaving the mixture determines the turbidity.

Question 34

Describe two ways to cultivate anaerobes.

Answer 34

reducing media or anerobe jar

Question 35

describe membrane filtration

Answer 35

cells in solution are poured through a membrane that catches the cells. Cells are transferred to media to be counted

Question 36

What macromolecules require sulfur and phosphorus?

Answer 36

amino acids and DNA/RNA

Question 37

define aerotolerant anaerobes, where they are in the tube, and an example

Answer 37

not killed by O2 but do not use it streptococci

Question 38

death/decline phase

Answer 38

cells die off due to waste or lack of space or nutrients

Question 39

Carbon source for photoheterotrophs

Answer 39

organic chemicals

Question 40

Which microbes have SOD, catalase, or peroxidase?

Answer 40

obligate anaerobes have SOD and catalase facultative anaerobes have SOD and catalase aertolerant anaerobes have SOD but no catalase

Question 41

log phase

Answer 41

exponential growth, most sensitive to antimicrobial agents

Question 42

Describe two ways to store bacterial cultures.

Answer 42

fridge, deep freeze, freeze-drying

Question 43

How are biofilms different than their single species counter parts?

Answer 43

act differently

Question 44

Which pH do pathogenic organisms grow best at?

Answer 44

6.5-7.5

Question 45

What are some sources of nitrogen that bacteria use?

Answer 45

free amino acids, peptides, and proteins. Some use N2 gas

Question 46

Energy source for phototrophs

Answer 46

light

Question 47

How do high concentrations of salt and sugar affect cells?

Answer 47

plasmolysis, cell membrane pulls away from cell wall

Question 48

How do differential and selective media differ? Can a medium be both selective and differential?

Answer 48

differential media- differentiates the growths by growing style (color changing) selective media- only allows for certain microbes to grow yes

Question 49

Describe flow cytometry

Answer 49

single file flow of cells flow through a machine and light scatter is used to count them

Question 50

Define inoculum and culture (note there are different ways to use the word culture: noun, verb, adjective).

Answer 50

inoculum- cultural medium that contains microbes culture (noun)- the thing you are growing culture (verb)- to culture a bacteria

Question 51

How does defined media differ from complex media?

Answer 51

defined media everything is known quantities in the media complex is a mixture of things and the exact quantities are not known