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ANS 302: Veterinary Microbiology > Microbial Growth > Flashcards

Microbial Growth Flashcards

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Biology 101 flashcards
1
Q

What is growth referring to in the case of bacteria?

A

Population growth.

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2
Q

What does growth result in an increase in?

A

Cellular constituents.

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3
Q

What are two possible results of an increase in cellular constituents?

A
  1. An increase in cell number.
  2. An increase in cell size.
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4
Q

What is a microbial growth curve?

A

A logarithmic curve that plots the observed growth pattern for microorganisms cultivated in batch culture.
*Has distinct phases.

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5
Q

What is the label for the X-AXIS of the microbial growth curve?

A

Time.

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6
Q

What is the label for the Y-AXIS of the microbial growth curve?

A

Number of cells.

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7
Q

What is the first phase on the microbial growth curve?

A

The lag phase.

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8
Q

What happens during the lag phase?

A

Synthesis of new components as the bacteria adapts to a new medium.
*May be absent if new medium is the same or similar to previous medium.

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9
Q

What is the second phase on the microbial growth curve?

A

The exponential/log phase.

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10
Q

What happens during the exponential phase?

A

The rate of division and growth is exponential.
*Population is most uniform.

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11
Q

What is the third phase of the microbial growth curve?

A

Stationary phase.

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12
Q

What happens during the stationary phase?

A

The reproductive rate and the death rate are balanced due to the threshold for total number of viable cells having been met.

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13
Q

What type of environment causes bacteria to enter the stationary phase?

A
  1. Nutrient limitation.
  2. Toxic waste accumulation.
  3. Limited oxygen availability.
  4. Critical population density reached.
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14
Q

What is the fourth phase of the microbial growth curve?

A

Death phase.

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15
Q

What happens during the death phase?

A

The number of viable cells exponentially declines at a constant rate due to environmental changes.

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16
Q

What are the two alternative hypotheses for what is happening during the death phase?

A
  1. Cells are viable, but not culturable (VBNC): Alive, but dormant and capable of new growth when conditions are right.
  2. Programmed cell death: Fraction of cell population is apoptotic at a certain threshold.
17
Q

What is stage five of the microbial growth curve?

A

Long-term stationary phase.

18
Q

What happens during the long-term stationary phase?

A

The bacterial population continues to evolve in waves of genetically distinct variants.
*Natural selection does occur.

19
Q

What is quorum sensing?

A

A bacterial cell-to-cell communication process that involves the production, detection, and response to autoinducers (Ais).

20
Q

Is quorum sensing density-independent or density dependent?

A

Density dependent.

21
Q

What is the relationship between bacterial population and Ais?

A

Positive correlation.

22
Q

What kinds of genes does quorum sensing control?

A

Genes that direct activities that are beneficial when performed by groups of bacteria acting in synchrony.
ex: Bioluminescence, sporulation, antibiotic production, biofilm formation.

23
Q

What is it called when microbes grow attached to a surface?

A

Sessile.

24
Q

What is it called when microbes are free floating?

A

Planktonic.

25
Q

What are biofilms?

A

Complex, attached, slime-enclosed communities of microbes.

26
Q

Where are biofilms ubiquitous?

A

Water, but can be formed on any surface.

27
Q

What is the first step of biofilm formation?

A

Reversible attachment of planktonic cells. Still individual microbes.
*Planktonic step.

28
Q

What is the second step of biofilm formation?

A

First colonizers become irreversibly attached.
*Attachment step.

29
Q

What is the third step of biofilm formation?

A

Growth and cell division.
*Growth step.

30
Q

What is the fourth step of biofilm formation?

A

Production of extracellular polymeric substance (EPS) and formation of water channels.
*Maturity step.

31
Q

What is the fifth step of biofilm formation?

A

Attachment of secondary colonizers and dispersion of microbes to new sites.
*Dispersion step.

32
Q

What does the EPS and changes in attached organisms’ physiology protect the bacteria from?

A

Harmful agents.

33
Q

What makes a biofilm heterogeneous?

A

Differences in the metabolic activity and locations of the resident microbes. Additionally, exchanges between the resident microbes take place through metabolism, communication, and DNA uptake.

34
Q

What does DNA uptake/transformation encourage?

A

Horizontal gene transfer.

ANS 302: Veterinary Microbiology (16 decks)

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