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Micro > L6: Microbial Growth > Flashcards

L6: Microbial Growth Flashcards

1
Q

define microbial growth

A

an increase in the number of cells in a population

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2
Q

What are the steps to binary fission?

A
  1. DNA replicatees
  2. Cell elongates, chromosomes segregate
  3. septum forms between two daughter cells
  4. cell divides
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3
Q

What is the name of a key bacterial cytoskeletal protein in bacteria and archaea

A

FtsZ

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4
Q

What is FtsZ

A

homologue of eukaryotic protein tubulin

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5
Q

What is FtsZ required for?

A

cell division and septum formation

it forms contractile ring at midcell

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6
Q

Where does FtsZ’s energy come from

A

hydrolysis of GTP

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7
Q

population growth is studied by analyzing_____

A

growth curve

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8
Q

What circumstances are used to form a growth curve?

A

microbes cultivated in a batch culture (closed vessel, single batch of medium)

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9
Q

What happens in the lag phase of the growth curve?

A

no growth, cells synthesizing new components

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10
Q

What happens in the log phase of the growth curve?

A

cells divide, exponential increase

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11
Q

What happens in the stationary phase of the growth curve?

A

population growth ceases because as the pop grows, toxic byproducts of replication accumulate and begin killing cells

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12
Q

What are spores?

A

stress-resistant, dormant cells that may form in microbes under nutrient limiting conditions

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13
Q

What are 3 methods of measuring microbial growth

A

direct cell counts (counting chambers)
viable cell counts (plating, CFUs)
turbidity measurements (spectrophotometer)

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14
Q

What are biofilms

A

microbial communities that are attached to a surface and covered with a protective matrix

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15
Q

What are the 4 phases of biofilm growth?

A

attachment
colonization
maturation
dispersal

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16
Q

What is present during attachment of biofilms?

A

pili and adherence proteins

17
Q

What is present during colonization of biofilms? What happens during this phase?

A

quorum sensing
cell-cell signaling

activates gene expression to make matrix of polysaccharides, protein, and DNA

18
Q

What happens during maturation of biofilms?

A

mushroom forms with channels for nutrients and oxygen gradients
can be aerobic or anaerobic

19
Q

What happens during dispersal of biofilms?

A

biofilm opens and planktonic cells are released

20
Q

What is periodontal disease?

A

microbial infection with inflammation and tissue destruction

21
Q

What is dental plaque?

A

microbial film on tooth surface

22
Q

What are some environmental factors that can influence microbial growth?

A

oxygen concentration
temperature
solutes and water activity
pH

23
Q

What are extremophiles?

A

microbes that grow in extremes environments

24
Q

What are obligate aerobes?

A

microbes that need oxygen

25
Q

What are facultative anaerobes?

A

microbes that prefer oxygen

26
Q

What are aerotolerant anaerobes?

A

microbes that ignore oxygen

27
Q

What are obligate anaerobes?

A

microbes that can’t tolerate oxygen/ oxygen is toxic

28
Q

What are microaerophiles?

A

microbes that need 2-10% oxygen

29
Q

What is the basis of different oxygen sensitivities?

A

oxygen can be reduced to toxic products called Reactive Oxygen Species like superoxide radical and hydrogen peroxide so microbes need enzymes to detoxify

30
Q

What enzymes can help detoxify oxygen products?

A 
superoxide dismutase (SOD)
catalase
31
Q

What temperatures can hyperthermophiles survive in?

A

> 80C

32
Q

What temperatures can thermophiles survive in?

A

40 - 80C

33
Q

What temperatures can mesophiles survive in?

A

20 - 45C

34
Q

What temperatures can psychrophiles survive in?

A

0 - 20C

35
Q

What do high temperatures do to microbes?

A

disrupt membranes, denature proteins and DNA

36
Q

How do thermophiles adapt to high temperatures

A

proteins stabilized through increased H and covalent bonds and with molecular chaperones and refold damaged proteins
DNA stabilized by synthesizing proteins to coat DNA
Membrane stabilized

Micro (15 decks)

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