Biology 121: Diversity, Structure and Function

Fall 2010Sonoma State University

Tom Buckley08 Sep 10

Prokaryote diversity and metabolism

Prokaryotes: 90% of all biomass on Earth

Two major groups: Bacteria and Archaea

Prokaryotic phylogeny

Archaea extremophilesdiverse metabolism

Bacteria familiar prokaryotesmany pathogens

Prokaryotic cells

0.5 - 5 m diameter

Staphylococcus (strep throat)

Escherichia coli (E. coli)

Borellia burgdorferi (lyme disease)

examples

Q: what is 1 m in terms of millimeters?

Prokaryotic cell surfaces

Bacteria: two groups

Gram-positive Gram-negative: double membrane

Archaea: no peptidoglycan'Gram stain'stains peptidoglycan

Prokaryotic cell surfaces

capsule:sticky polysaccharides

Streptococcus tonsil tissue

protects againstphagocytosis & detergents

phago- = eatcyto = cell

Internal structure

(Heterotrophic) (Autotrophic)

Prokaryotic DNA

Much less DNA than eukaryotes

Organised in circularchromosomes

one very large loop

+ numerous very small ones (plasmids)

Plasmids in biotechnology

Cut plasmid withrestriction enzyme

Add DNA fragment w/new gene

Plasmid recombinesw/ fragment

Infect plant cellsw/ bacterium

Q: which plant cells should you infect?

Prokaryotic reproduction

Binary fission identical copy

Conjugation: one-way DNA transfer

Prokaryotic reproduction

Fission every 20 min - 24 hours

How long would it take to produceenough bacteria to reach the sun?

bacterium: 2 m longfission rate: every 3 hourssun distance: 150 million km

Prokaryotic reproduction

Short generation times

Frequent mutation

Huge population sizes

Strong selection

Extremely fast evolution

Prokaryotic evolution: example

grew bacteria in low-glucose solutions

periodically compare fitness against ancestral population

RESULT

Prokaryotic evolution: example

grew bacteria in low-glucose solutions

periodically compare fitness against ancestral population

Possible interpretation...

ancestral populationalso evolved

Control to rule this out...

RESULT

answer in class

something else in the solutionfavoured the new population

answer in class

Metabolism

Metabolism

MetabolismFood = electron donorNADH = electron carrierO2 = electron acceptor

Metabolism Aerobic respiration

CO2 CH2O

ATP ADP

energy

electrons

O2H2O

oxidation

ATP ADP

MetabolismFood = electron donorNADH = electron carrierO2 = electron acceptor

Aerobic respirationAnaerobic respiration

CH2O

ATP ADP

energy

O2H2O

lactate orethanol + CO2 CO2

CH2O

ATP ADP

energy

electrons

O2H2O

ATP ADP

x

oxidation

ATP ADP

Aerobic respirationPhotosynthesis

CO2 CH2O

oxidation

ATP ADP

energy

electrons

O2H2O

ATP ADP

CO2 CH2Oreduction

solarenergy

electrons

O2H2O

ATP ADP

Aerobic respirationPhotosynthesis

CO2 CH2O

oxidation

ATP ADP

O2H2O

CO2 CH2Oreduction

O2H2O

Prokaryotic metabolism: diversity

Prokaryotic metabolism: ecology

1. Nitrogen fixation

NH3

organic N

N2

1

2. Ammonification

organic NNH32

NO3

3. Nitrification

3

4. Denitrification

NOx

4

4

Nitrogen fixation (requires anaerobic conditions)

Prokaryotic metabolism

O2

N N

Nitrogen fixation (some plants)

Prokaryotic metabolism: symbiosis

Gut digestion (many animals, incl. ruminants & humans)

legume family (beans)many others

nodules

Prokaryotic metabolism: ecology

1. Nitrogen fixation

NO3

3. Nitrification

4. Denitrification

NOx

NH3

organic N

N2

1

2. Ammonification

organic NNH323

4

4

Q: What would happen to atmospheric N2

without N-fixing prokaryotes?

Prokaryotic metabolism: ecology

1. decomposition

CO2

organic C

organic C1

Q: What would happen to atmospheric CO2

without decomposing prokaryotes?

2. photosynthesis

3. death/senescence

2

3

Biotech

Prokaryotes: relevance to humans

Gut digestion

Pathogens

Ecology & agriculture:

decomposition (C & N cycling)

bioremediation (many pollutants)

synthetics (plastics, ethanol)

rapid evolution --> antibiotic resistance