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Microbiology > Lecture 7: Bacterial Nutrition > Flashcards

Lecture 7: Bacterial Nutrition Flashcards

1
Q

Autotrophy

A

don’t need organic carbon for energy or structural carbon

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2
Q

phototrophy

A

light

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3
Q

lithotrophy

A

inorganic non-carbonaceous material for energy

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4
Q

heterotrophy

A

use reduced organic carbon
- parasite/pathogen
- saprophyte

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5
Q

What are the major nutrients?

A
  • carbon
  • nitrogen
  • sulfur
  • phosphorus
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6
Q

Carbon

A

 About 50% of cell mass is carbon
- Either derived from inorganic or organic sources

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7
Q

Nitrogen

A

 Some bacteria fix nitrogen directly from the
atmosphere
 Some use ammonia or organic nitrogen from
digested macromolecules
 Nitrogen makes up about 15% of cell “dry weight”

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8
Q

Sulfur and phosphorus

A

 Between them, sulfur and phosphorus make up
about 4% of cell dry weight
 Essential in protein, DNA structure, ATP

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9
Q

Organic trace elements

A

Essential in synthesis of cofactors such as FAD, NAD, CoA

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10
Q

Examples of inorganic trace elements

A

magnesium, molybdenum, iron, copper, and zinc
- These are required for growth, but are usually present in tap water in sufficient quantities

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11
Q

What functions require certain inorganic trace elements?

A

many enzymatic functions
- These are required for growth, but are usually present in tap water in sufficient quantities

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12
Q

Oxygen

A

present in many, many forms
 Water, Carbon Dioxide, Oxygen Gas
 Reactive forms such as peroxide, hydroxyl radicals

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13
Q

molecular oxygen is…

A

an essential nutrient for some organisms, a deadly
poison for others
 Bacterial use enzymes to detoxify various reactive oxygen forms-hydrogen peroxide, free radicals
 Superoxide dismutase, Catalase

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14
Q

How do obligate aerobes respond to oxygen?

A

cannot grow well in the absence of oxygen

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15
Q

How do facultative anaerobes respond to oxygen?

A

grow using fermentation pathways in the absence of O2

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16
Q

How do microaerophiles respond to oxygen?

A

grow only in the presence of small concentrations of molecular oxygen

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17
Q

How do aerotolerants respond to oxygen?

A

anaerobes can survive in the presence of oxygen, but cannot grow

18
Q

How do obligate anaerobes respond to oxygen?

A

are killed by oxygen radicals generated in cells in the presence of oxygen

19
Q

Scarce nutrients must be scavenged from…

A

the environment

20
Q

Passive and active mechanisms for nutrient uptake

A
  • symport and antiport
  • ATP-binding cassette
21
Q

PTS System

A
  • transport of glucose across membrane
  • high energy PEP transfers Pi to glucose (group translocation)
  • other sugars can be transported analogously
22
Q

What is often the limiting nutrient in the environment?

A

phosphate

23
Q

What is the limiting nutrient in culture?

A

can be anything

24
Q

What is often the limiting nutrient in pathogens?

A

often iron

25
Q

What methods have bacteria developed to obtain limiting nutrients?

A
  • phosphatases
  • siderophores
26
Q

How to make laboratory cultures

A
  • start with sterile medium, defined or undefined
  • media may be solid (add agar) or liquid
  • add an inoculum, either of pure bacteria from a single species or a mixture (ex: soil or blood)
  • the microbes multiply in the medium as it is incubated and the result is a culture
27
Q

Nutrient Broth

A
  • Nutrient Broth
     Peptone (protein digest) 5g
     Beef extract 3g
     NaCl 8g
     Water 1L
28
Q

Defined E. Coli Medium (simple)

A

 Glucose 5g
 Ammonium Phosphate, monobasic 1g
 NaCl 5g
 Magnesium Sulfate, hydrated 0.2g
 Potassium phosphate, dibasic 1g
 Water 1L

29
Q

Aerobic Growth

A
  • easier
  • incubator for constant temperature
  • medium composition tends to be less complicated
30
Q

Anaerobic Growth

A
  • needs airtight chamber or anaerobic hood
  • obligate anaerobes are killed by exposure to O2
  • Obligate anaerobes need a reducing agent to be added
31
Q

Anaerobic Jars

A

 Put plates in a sealed jar containing a special
salt packet
 When the packet is
opened, water added, chemical reaction
occurs, generates CO2
and hydrogen gas
 Palladium catalyst allows reaction of oxygen and hydrogen to form water

32
Q

What organism grows in amadillos?

A

Mycobacterium leprae

33
Q

What grows in mammalian cell tissue culture?

A

Obligate intracellular bacteria such as Chlamydiae and Rickettsiae can only be grown as parasites

34
Q

Capnophiles

A

may desire high CO2 levels

35
Q

Uses of general growth media

A
  • used to produce large populations of bacteria for many purposes (research, industrial processes)
36
Q

Uses of selective and differential media

A

used to identify and detect specific organisms from various environmental sources
- especially relevant in clinical or public health settings

37
Q

Enrichment Culture

A

 Attempts to find organisms with certain biological characteristics
 May be ability to use a particular carbon, nitrogen, or energy source, or to withstand certain environmental stresses
 A sample from soil might be incubated in the presence of DDT as the only source of
carbon, and only organisms capable of degrading this pesticide would grow
 The organisms that grow could then be isolated

38
Q

Isolation (pure culture)

A

 When a sample is taken from the environment, it can be plated onto solid
media, where isolated colonies will grow
 Repeatedly using this procedure, isolates
can be obtained from even very dense cultures containing many species
 Streak plate method

39
Q

Culture preservation

A
  • Agar plates will sustain a bacterial culture in the refrigerator for at most ~6 months
  • freeze-drying (lyophilization)
  • freeze at -80C with 15% glycerol to prevent ice crystals from destroying the cells
40
Q

Slide 7 (left to right)

A
  1. Obligate anaerobe?
  2. aerotolerant?
  3. microaerophile?
  4. obligate aerobe?

Microbiology (16 decks)

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