Post on 20-Dec-2015
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+