Chapter 9

Question 1

What does bacterial growth refers to?

Answer 1

Bacterial growth refers to the bacterial population growth

Question 2

How do prokaryotes reproduce?

Answer 2

ALWAYS asexual reproduction! Through Binary Fission, but some exceptions.

Question 3

Where does replication start?

Answer 3

Starts at the origin of replication on circular chromosomes

Question 4

How does the cell cytoplasm divide?

Answer 4

Divides in the process of cytokinesis

Question 5

What protein directs cytokinesis and cell division?

Answer 5

FtsZ : assembles into a Z ring on the cytoplasmic membrane

Question 6

What is the Divisome?

Answer 6

Activates to produce peptidoglycan cell wall and build a septum that divides the two daughter cells.

Question 7

What is the difference between generation/doubling time in Eukaryotes and Prokaryotes?

Answer 7

Eukaryotes: The time between the same points of the life cycle in two successive generations.

Prokaryotes: The time it takes for the population to double through one round of binary fission.

Question 8

Nt = N0 x 2^n
log10(Nt) = log10(N0 x 2^n)
n = (log10(Nt) - log10(N0)) / (log10(2))
k = n/t
g = (1/k) = (t/n)

Answer 8

KNOW THESE EQUATIONS!!!

This is only working if we assume the generation time is not changing and remains the same indefinitely, HOWEVER likely not the case

Question 9

What does k stand for?
What does g stand for?
What does n stand for>

Answer 9

k = The number of generations per unit of time
g = generation time
n= the number of generations

Question 10

What is the growth curve? What are the phases of the growth curve?

Answer 10

Growth curve: a graph modeling the number of cells in the culture over time. Distinct phases
- x = Logarithm of living bacterial cells
- y = Time
Lag phase, Log phase, Stationary phase, Death/Decline phase

Question 11

What is Culture Density?

Answer 11

Culture density: defined as the number of cells per unit volume

Question 12

Explain the Lag Phase

Answer 12

Lag phase: no increase in number of living bacterial cells.
Duration depending on :
- the species and genetic make-up of the cells.
- the composition of the medium
- the size of the original incolum

Inoculum: a small number if cells that is represented in the beginning of the growth curve.
- added to fresh culture medium, cells gearing for the next growth phase. Observed cells don’t change.

Question 13

Explain the Log Phase

Answer 13

Log phase: Exponential increase in number of living bacterial cells. Cells are actively dividing by binary fission and their number increases exponentially (not linear). Shows constant growth rate, uniform metabolic activity

** growth rate is genetically determined generaation time under specific conditions for a specific bacterial strain. **

Question 14

Explain Stationary Phase

Answer 14

Stationary phase: slows/stalls pop. growth due to unfavorable conditions (waste products accumulate, nutrients get used up, O2 decrease & limit aerobic cell growth). Live cells reaches plateau but still active.

New Cells = Cells death
Total pop. of living cells & Cell density = constant

Cells -> survival mode of metabolism. Slow synthesis of peptidoglycan, proteins, and nucleic acids.

** Sporulation or Secondary metabolic production (antibiotics) eventually happens***

Question 15

Explain Death phase

Answer 15

Death Phase: accumulation of toxic waste and nutrients are exhausted, cell die in greater and greater numbers.

Exponential decrease in the number of cells

Question 16

What is a chemostat?

Answer 16

Chemostat: used to maintain a continuous culture where nutrients are supplied at a steady rate to maintain cells in log phase (cell develop > cell death)

an opening to add nutrients (feed) and an outlet to remove contents (effluent)

Question 17

What is bacterial counts? Bacterial Load?

Answer 17

Bacterial counts: consist in estimating the number of bacterial cells in a sample

Bacterial Load: The number of bacteria in a clinical sample

Question 18

Direct methods v.s Indirect methods

Answer 18

-Direct methods: Involve counting cells

• Indirect methods: Depend of the measurement of cell presence or activity without counting individual cells.

Question 19

Primary v.s. Secondary Stain

Answer 19

Primary Stain: (green fluorescence) penetrate cytoplasmic membranes, staining both live and dead cells

Secondary Stain: (red fluorescence) stains cells only if the cytoplasmic membrane is damaged

Question 20

Viable/simply plate count

Answer 20

a count of viable or live cells, based on the principle that viable cells replicate and give rise to visible colonies when incubated under suitable conditions for the specimen.

Question 21

What does the pH indicator do?

Answer 21

pH indicator that changes color from red to yellow when the lactose is fermented.

Question 22

What is turbidity and what measures it?

Answer 22

Turbidity: cloudiness
** measures turbidity of a sample bacteria in a liquid suspension**
Spectrophotometer measures turbidity

Question 23

What happens when the number of bacteria in a suspension increase

Answer 23

As the number of bacteria in a suspension increase, the turbidity also increases and causes less light to reach the detector.

Question 24

Calibration curve

Answer 24

Calibration curve is generated by plitting turbidity v.s. cell density

Calibration curve can be used to estimate cell counts for all samples obtained or cultured under similar conditions and with densities within teh range of values used to construct the curve

Question 25

What is biofilms?

Answer 25

Biofilms: microorganisms grow mainly in biofilms
- Complex and dynamic ecosystems that form on a variety of environmental surfaces.

Question 26

What is EPS?

Answer 26

Extracellular polymeric substances: biofilms secrete an extracellular matrix

Question 27

What is Planktonic cells?

Answer 27

Planktonic cells: Free-floating microbial. The formation of a biofilm essentially involves the attachment of planktonic cells to a substrate. Becomes sessile

Question 28

Pathogens embedded within biofilms…

Answer 28

Pathogens embedded within biofilms exhibit a higher resistance to antibiotics than their free-floating counterpart.

Question 29

After cyanobacteria released O2 as a byproduct of photosynthesis & iron intake from the ocean was exhausted, O2 lvls increased in atmosphere. What was the effect?

Answer 29

This caused a massive extinction bc most organisms could not survive the oxidative properties of reactive oxygen species (ROS)

Question 30

What is Reactive Oxygen Species (ROS)?

Answer 30

ROS: unstable ions and molecules derived form partial reduction of O2 that can damage virtually any macromolecules or structure with which they come in contact

Question 31

What are the three main enzymes that break down those toxic byproducts?

Answer 31

Superoxide dismutase (SOD): break down the powerful superoxide anions generated by aerobic metabolism
Peroxidase
Catalase: converts hydrogen peroxide to water and oxygen

Question 32

Obligate v.s. Aerotolerant

Answer 32

Obligate: Lack the 3 enzymes
Aerotolerant: has SOD but NO Peroxidase and NOT Catalase