Lecture 7: Bacterial Nutrition

Question 1

Autotrophy

Answer 1

don’t need organic carbon for energy or structural carbon

Question 2

phototrophy

Answer 2

light

Question 3

lithotrophy

Answer 3

inorganic non-carbonaceous material for energy

Question 4

heterotrophy

Answer 4

use reduced organic carbon
- parasite/pathogen
- saprophyte

Question 5

What are the major nutrients?

Answer 5

• carbon
• nitrogen
• sulfur
• phosphorus

Question 6

Carbon

Answer 6

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

Question 7

Nitrogen

Answer 7

 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”

Question 8

Sulfur and phosphorus

Answer 8

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

Question 9

Organic trace elements

Answer 9

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

Question 10

Examples of inorganic trace elements

Answer 10

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

Question 11

What functions require certain inorganic trace elements?

Answer 11

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

Question 12

Oxygen

Answer 12

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

Question 13

molecular oxygen is…

Answer 13

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

Question 14

How do obligate aerobes respond to oxygen?

Answer 14

cannot grow well in the absence of oxygen

Question 15

How do facultative anaerobes respond to oxygen?

Answer 15

grow using fermentation pathways in the absence of O2

Question 16

How do microaerophiles respond to oxygen?

Answer 16

grow only in the presence of small concentrations of molecular oxygen

Question 17

How do aerotolerants respond to oxygen?

Answer 17

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

Question 18

How do obligate anaerobes respond to oxygen?

Answer 18

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

Question 19

Scarce nutrients must be scavenged from…

Answer 19

the environment

Question 20

Passive and active mechanisms for nutrient uptake

Answer 20

• symport and antiport
• ATP-binding cassette

Question 21

PTS System

Answer 21

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

Question 22

What is often the limiting nutrient in the environment?

Answer 22

phosphate

Question 23

What is the limiting nutrient in culture?

Answer 23

can be anything

Question 24

What is often the limiting nutrient in pathogens?

Answer 24

often iron

Question 25

What methods have bacteria developed to obtain limiting nutrients?

Answer 25

- phosphatases - siderophores

Question 26

How to make laboratory cultures

Answer 26

- 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

Question 27

Nutrient Broth

Answer 27

- Nutrient Broth  Peptone (protein digest) 5g  Beef extract 3g  NaCl 8g  Water 1L

Question 28

Defined E. Coli Medium (simple)

Answer 28

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

Question 29

Aerobic Growth

Answer 29

- easier - incubator for constant temperature - medium composition tends to be less complicated

Question 30

Anaerobic Growth

Answer 30

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

Question 31

Anaerobic Jars

Answer 31

 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

Question 32

What organism grows in amadillos?

Answer 32

Mycobacterium leprae

Question 33

What grows in mammalian cell tissue culture?

Answer 33

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

Question 34

Capnophiles

Answer 34

may desire high CO2 levels

Question 35

Uses of general growth media

Answer 35

- used to produce large populations of bacteria for many purposes (research, industrial processes)

Question 36

Uses of selective and differential media

Answer 36

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

Question 37

Enrichment Culture

Answer 37

 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

Question 38

Isolation (pure culture)

Answer 38

 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

Question 39

Culture preservation

Answer 39

- 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

Question 40

Slide 7 (left to right)

Answer 40

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