Describing Prokaryotes

handout

prokaryotic vs. eukaryotic cells

Describing Prokaryotes

1. Phylogeny• Comparison of conserved genes (16S

rRNA)• Can group to species or sometimes sub-

species level• Does not always predict function or

metabolic capabilities (phylogeny ≠ function)

Describing Prokaryotes

1. Phylogeny

2. Physiology/Metabolism– Source of C– Source of energy– Electron acceptors

Electron Acceptors

• Internal and Organic =

• Oxygen =

• NO3-, Fe(III), SO4

2- , CO2 =

How organotrophs and lithotrophs make energy

Thermodynamics Oxidation/Reduction couples

•More Oxidized•More willing to take up electrons

•More reduced•More able to give up electrons

• Autotrophy – use CO2 as C – Phototrophy

• Oxygenic – produces O2 (electrons come from H2O)• Anoxygenic – no O2 production

– Electron donor» H2

» H2S, So

» Organic C» Fe2+

– Lithotrophy – use inorganic chemical as energy• Energy source

– H2

– HS-,So,S2O32-

– NH4, NO3-

– Fe2+

– Mn2+

• Heterotrophy – use organic C as C source• Fermentation• Aerobic respiration

– Electron Acceptor» O2

• Facultative– Electron acceptor

» Use O2 when available» Use fermentation or NO3

- when no O2

• Anaerobic respiration– Electron Acceptors

» NO3-, NO2-

» So, S2O32-, SO3

2-, SO42-

» Fe3+, Mn4+

» CO2

» Fumarate (organic C)

Describing Prokaryotes

1. Phylogeny

2. Physiology/Metabolism

3. Form & Structures• Cell wall - Gram positive, Gram negative,

Acid-fast• Endospores producing• Filamentous, motility, colony morphology…

Describing Prokaryotes

1. Phylogeny2. Physiology/Metabolism3. Form & Structures4. Habitat

• Temperature• pH• Pressure• Nutrient availability• Salinity

Describing Prokaryotes

1. Phylogeny

2. Physiology/Metabolism

3. Form & Structures

4. Habitat

5. Other functions/processes• N2 fixation

• Antibiotic production• pathogens

Examples

• Escherichia coli

• Methanococcus (lives in cattle gut, produce methane)

• Thiobacillus - example reaction

H2S +O2 SO42- + 2H+

• Geobacter metallireducens –acetate- + 8Fe3+ + 4H2O 2HCO3

- + 8Fe2+ + 9H+