chapter 5 Brock

Question 1

Define microbial growth

Answer 1

an increase in cell numbers.
the final result of of the doubling of all cell components prior to actual division that yields two daughter cells.
most microorg. grow by binary fission.

Question 2

binary fission is…

Answer 2

cell division following enlargement of a cell to twice its minimum size

Question 3

biofilm

Answer 3

an attached polysaccharide matrix containing bacterial cells

Question 4

bacteriocidal agent

Answer 4

an agent that kills bacteria

Question 5

bacteriostatic agent

Answer 5

an agent that inhibits bacterial growth

Question 6

divisome

Answer 6

a complex of proteins that directs cell division processes in prokaryotes

Question 7

exponential growth

Answer 7

growth of a microbial population in which cell numbers double within a specific time interval

Question 8

germicide (antiseptic)

Answer 8

a chemical agent that kills or inhibits growth of microorganisms and is sufficiently nontoxi to be applied to living tissues

Question 9

halophile

Answer 9

a microorganism that requires NaCl for growth

Question 10

halotolerant

Answer 10

a microorganism that does not require NaCl for growth but can grow in the presence of NaCl, often high levels

Question 11

HEPA filter

Answer 11

a high-efficiency particulate air filter that removes particles, including microorg from intake or exhaust air flow.

Question 12

hyperthermophile

Answer 12

a prokaryote that has a growth temperature optimum of 80 deg C or greater

Question 13

mesophile

Answer 13

an organism that grows best at temperatures between 20 and 40 deg C

Question 14

microaerophile

Answer 14

an aerobic organism that can grow only when O2 tensions are reduced from that present in air

Question 15

minimum inhibitory concentration (MIC)

Answer 15

the min. conc. of a substance necessary to prevent microbial growth

Question 16

neutrophile

Answer 16

an organism that grows best at neutral pH, between pH 5.5 and 8.

Question 17

obligate anaerobe

Answer 17

an organism that cannot grow in the presence of O2

Question 18

osmophile

Answer 18

an organism that grows best in the presence of high levels of solute, typically a sugar

Question 19

plate count

Answer 19

a method of counting viable cells; the number of colonies on a plate is used as a measure of cell numbers

Question 20

psychrophile

Answer 20

an organism with a growth temperature optimum of 15 deg C or lower and a max growth temp below 20 deg C

Question 21

psychrotolerant

Answer 21

capable of growing at low temperatures but having an optimum above 20 deg C

Question 22

sanitizer

Answer 22

an agent that reduces microorg to a safe level but may not eliminate them

Question 23

sterilant/steriliser/sporicide

Answer 23

a chemical agent that destroys all forms of microbial life

Question 24

sterilisation

Answer 24

the killing or removal of all living organisms and viruses

Question 25

thermophile

Answer 25

an organism whose growth temperature optimum lies between 45 and 80 deg C

Question 26

transpeptidation

Answer 26

formation of peptide crosslinks between muramic acid residues in peptidoglycan synthesis

Question 27

viable

Answer 27

capable of reproducing

Question 28

viable count

Answer 28

a measurement of the conc. of live cells in a pop.

Question 29

xerophile

Answer 29

an organism that is able to live, or that lives best, in very dry environments.

Question 30

What are the roles of Fts proteins in cell division and chromosome replication?

Answer 30

With the help of MinE, FtsZ defines the cell division plane and helps assemble the divisome, the protein complex that orchestrates cell division

Question 31

What’s the role of MreB?

Answer 31

MreB helps define cell shape, and in rod-shaped cell walls, MreB forms a cytoskeletal coil that directs cell wall synthesis along the long axis of the cell.

Question 32

What is the equivalent of MreB in Caulobacter?

Answer 32

Crescentin plays analogous role to MreB in Caulobacter, leading to formation of a curved cell.

Question 33

How is new cell peptidoglycan synthesised during bacterial cell growth?

Answer 33

by the insertion of new glycan tetrapeptide units into preexisting peptidoglycan.
Bactoprenol facilitates transport of these units through the cytoplasmic membrane.
Transpeptidation completes the process of cell wall synthesis by cross-linking adjacent ribbons of peptidoglycan at muramic acid residues.

Question 34

Typical microorganism growth pattern?

Answer 34

When inoculated into a fresh culture medium:
lag phase, exponential growth, [essential nutrients depleted & toxic products build up] growth ceases and population is in stationary phase. Further incubation can lead to cell death.

Question 35

What’s a chemostat?

Answer 35

An open system used to maintain cell populations in exponential growth for extended periods [controls the dilution of culture with fresh culture medium, and conc. of growth limiting nutrients dissolved in medium]

Question 36

When do we use counting chambers?

Answer 36

Microscopic counts measure the total no. of cells in a sample - good for assessing the total cell numbers in a microbial habitat.

Question 37

Are viable cell counts (plate counts) accurate?

Answer 37

They measure only the living population present in the sample with the assumption that each colony originates from the growth and division of a single cell. Depending on the growth medium and conditions used, can be fairly accurate or highly unreliable. Repeats?

Question 38

Are turbidity measurements useful?

Answer 38

Indirect, very rapid way of measuring microbial growth. Need to establish a standard curve of turbidity value and direct cell number first, for comparison of samples.

Question 39

Abiotic factors affecting microbial growth?

Answer 39

Temperature;
pH;
water;
oxygen

Question 40

Some of those funny -phile names please!

Answer 40

Psychrophiles - opt below 20 deg C
Thermophiles - opt between 45 and 80 deg C
Hyperthermophiles - opt above 80 deg C
Acidophiles - opt low pH
Alkaliphiles - opt high pH