BIOL240 Chapter Notes -Purple Sulfur Bacteria, Alphaproteobacteria, Methane Monooxygenase

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MODULE 8
Part A: The Proteobacteria
Overview
Phylogenic Overview
- Proteobacteria purple bacteria
- Purple phototrophic bacteria are members
- Other members: methanotrophs, Pseudomonas type organisms, free-living aerobic
nitrogen-fixing organisms, Neisseria and its relatives, enteric bacteria
The Proteobacteria
- Proteobacteria divided into different groups phylogenetic groupings based on 16S
rRNA sequence
- Many are photosynthetic
- Gram-negative bacteria
- Ancestral phototroph delta purple, epsilon purple, gama purple, alpha purple and
beta purple bacteria
- Rhodo- bacteria red
- Pseudomonas plant/human pathogens, non-pathogenic
- Escherichia human pathogen
Purple Phototrophic Bacteria
Overview
- Microorganisms are pigmented
- Carry out anoxygenic photosynthesis no oxygen production
- Oxygen inhibits photosynthesis only in anaerobic conditions
- Some can grow aerobically using respiration
- No photosynthesis under aerobic conditions
- Pigments bacterial chlorophylls and carotenoids
- Colour determines which wavelengths of light it can best absorb
- Phototrophs photoautotrophs (C = carbon dioxide) and Photoheterotrophs (C =
organic)
- Photosynthesis takes place in intracellular membrane folds
Environment
- Found in high H2S gas environments
- H2S gas can be used as electron donor in CO2 reduction process
- Below surface of lake water
Purple Sulfur Bacteria
- Photoautotrophs oxidize H2S to elemental sulfur
- Elemental sulfur stored in periplasm
- Under anoxic conditions
- All purple sulfur bacteria are members of gamma proteobacteria grouping
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Purple Nonsulfur Bacteria
- No H2S oxidation
- Some can carry out low level of H2S oxidation
- Photoheterotrophs carbon from organic sourse
- Fix nitrogen
- Members of alpha and beta proteobacteria grouping
Methanotrophs
Overview
- Organism capable of oxidizing methane as an electron donor in energy metabolism
- Methylotroph: capable of oxidizing compounds like methanol
- Only organisms capable of oxidizing methane
- Methane C1 compound without C-C bond
- Unable to utilize compounds containing C-C bonds
- Restricted in types of environments they can inhabit
- Methane monooxygenase important enzyme used in conversion of methane to
methanol
- Obligate aerobes further restricting environments inhabited
Environment
- Biologically produced methane anaerobic conditions but used by organisms with
oxygen requirement
- Methane diffuses from anoxic zone to oxic zone at thermocline
- Region of sufficient oxygen and methane
- Methane formed: ocean floor, rumen of cows and other ruminants, swamps and
wetlands, anaerobic digesters of waste environemtn
- Symbiotic interactions between marine mussles and methanotrophs
Pseudomonads and Nitrogen-Fixing Bacteria
Pseudomonads
- Heterogenous group
- Classified as aerobic chemoorganotrophs
- Nutritionally versatile
- Polar flagella
- Different environments soils, water, animal and plant pathogens
Free Living Aerobic Nitrogen-Fixing Bacteria
- Fix nitrogen under aerobic conditions while growing on their own in environment
- Azotobacter highest respiration rates and strict aerobes
- Nitrogen fixation carried out by nitrogenase enzyme ocygen sensitive
- N-fixing organisms have interactions with hosts which shield them from high levels of
oxygen or fix nitrogen anaerobically
- Thick slime layer that coats cell
- Oxygen diffuses into cell through slime layer but used at high rate that intracellular
oxygen levels are low
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Document Summary

Other members: methanotrophs, pseudomonas type organisms, free-living aerobic nitrogen-fixing organisms, neisseria and its relatives, enteric bacteria. Proteobacteria divided into different groups phylogenetic groupings based on 16s rrna sequence. Ancestral phototroph delta purple, epsilon purple, gama purple, alpha purple and beta purple bacteria. Carry out anoxygenic photosynthesis no oxygen production. Oxygen inhibits photosynthesis only in anaerobic conditions. Colour determines which wavelengths of light it can best absorb. Phototrophs photoautotrophs (c = carbon dioxide) and photoheterotrophs (c = organic) H2s gas can be used as electron donor in co2 reduction process. All purple sulfur bacteria are members of gamma proteobacteria grouping. Some can carry out low level of h2s oxidation. Members of alpha and beta proteobacteria grouping. Organism capable of oxidizing methane as an electron donor in energy metabolism. Methylotroph: capable of oxidizing compounds like methanol. Methane c1 compound without c-c bond. Methane monooxygenase important enzyme used in conversion of methane to. Restricted in types of environments they can inhabit methanol.

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