Chapter 9 - Microbial Growth

Question 1

The growth of individual cells is _________________.

Answer 1

Exponential

Question 2

The exponential growth of individual cells is a simple consequence of the ___________________ nature of the growth process.

Answer 2

Autocatalytic

Question 3

What do we mean when we say that exponential growth is the result of autocatalytic nature?

Answer 3

The process of growth involves the synthesis of new macromolecules from simple precursor molecules, which requires catalysts that are themselves macromolecules. Thus, growth involves the synthesis not only of new structures but also of new catalysts for growth as well. The catalytic capacity of the cell increases steadily through the life cycle and hence the absolute rate of growth increases as well

Question 4

Be familiar with the following figure.

Answer 4

Question 5

A common way prokaryotes divide is by _______________ ______________.

Answer 5

Binary fission

Question 6

Cell division in most prokaryotic cells involves inward growth of a ___________________.

Answer 6

Septum

Question 7

The mechanism controlling septation is still unclear, but it involves the ring of the protein __________ that assembles just below the cell membrane around the equator of the cell when DNA replication finishes.

Answer 7

FtsZ

Question 8

________ is analogous to tubulin.

Answer 8

FtsZ

Question 9

Some cells divide by _______________, an unequal division, or multiple fission.

Answer 9

Budding

Question 10

What is multiple fission?

Answer 10

A few prokaryotes grow until the mother cell is many times the size of a baby cell and then undergo multiple rounds of division without any additional growth

Question 11

The _______________ _______ is the period between the “birth” of a cell by division of its mother cell and its own division into two baby cells.

Answer 11

Interdivision time

Question 12

What is the most common measure of growth rate?

Answer 12

Generation time

Question 13

What is “generation time”?

Answer 13

The time it takes for a population to double in number

Question 14

Growth rates typically vary over about a __-fold range.

Answer 14

10

Question 15

Bacterial chromosomes replicate ___________________ from a _____________ origin.

Answer 15

Bidirectionally

Single origin

Question 16

In bacteria, successive cell cycles can overlap. Why is this significant?

Answer 16

Because “grandma” E. coli, for example, began making chromosomes for grandaughter cells when the daughter cell was born

Question 17

The ___ period is the amount of time it takes for the bacterial chromosome to be replicated.

Answer 17

C period

Question 18

In the __ period, division ocurs.

Answer 18

D period

Question 19

There is an obligatory period of __ minutes between the completion of chromosome replication and cell division.

Answer 19

20 minutes

Question 20

There is no obligatory G1 period; however, when the enviornment constrains growth to a generation time longer than __ minutes, there is a period equivalent to G1, and as the growth rate gets ______________, the gap gets _______________ until it disappears entirely at a generation time of __ minutes.

Answer 20

60 minutes

Shorter

Shorter

60 minutes

Question 21

As the population grows increasingly quickly, the ___________________ time for DNA replication is pushed back further in the previous cycle.

Answer 21

Initiation

Question 22

What are two reasons for the rapid growth rates seen in bacteria?

Answer 22

1. Dispense with G1
2. Overlap their cell cycles

Question 23

At what point are bacterial cells least able to handle stress?

Answer 23

Cellular division

Question 24

Microbial population growth is normally measured by ____________________.

Answer 24

Spectrophotometry

Question 25

A ___________________ is an instrument that shines light of a chosen wavelength through a specimen and determines the amount that gets through.

Answer 25

Spectrophotometer

Question 26

Microbial population growth is __________________.

Answer 26

Exponential

Question 27

What is the instantaneous growth rate proportional to?

Answer 27

The number of cells present

Question 28

When are generation times calculated?

Answer 28

During the exponential phase of growth

Question 29

How do can you calculate the doubling time or generation time (g)?

Answer 29

From a natural log plot

y = kN, where k is the growth rate constant and equivalent to the slope of the line

If N = 2, the point at which the population has doubled, the equation can be re-written as ln(2) = kg

Once k (slope) is determined, g or doubling time can be determined 0.6931/k = g

Question 30

Populations enter ________________ phase when they run out of nutrients or accumulate toxic quantities of waste materials.

Answer 30

Stationary phase

Question 31

Cells that have been in exponential growth for several generations are in ________________ growth.

Answer 31

Balanced

Question 32

When do most mutations occur?

Answer 32

Stationary phase

Question 33

You must be able to label a standard growth curve.

Answer 33

Question 34

When should tests on bacterial cells be completed?

Answer 34

During log phase/exponential phase

Question 35

Why should tests be done during the log/exponential phase?

Answer 35

A culture growing exponentially remains quite constant in all of its important properities (average cell size, macromolecular composition, etc), and physiological experiments done on such cultures are much more reproducible