21: Bacterial Phototrophy Flashcards
Name characteristcs of bacterial phototrophs
- cytoplasmic membrane infoldings via thylakoids in cyanobacteria, chromomes…
- green/purple sulfur bacteria accumilate S0 intracellular or intracellularly
- Green/purple NS bacteria may use sulfide as e- donors but not accumulate S0
List phenotypic characteristics of bacterial phototrophs
Green bacteria are green or brown.
Purple bacteria can be yellow, orange, green, purple or red
Cyanobacteria can be green or blue
What 5 criteria can you use to distinguish bacteria CPEAP
pigments, photosystems, C source, E donor, aeorbic dark growth
Characterise Cyanobacteria using the five criteria
– Pigments: chlorophyll-a (rarely chlorophyll-b)
– Photosystems: two, occasionally only one
– Carbon source: CO2 , organic compounds sometimes
– Electron donor: H2 O, occasionally H2 S or organic compounds
– Aerobic dark growth?: No
Describe cyanoabacterium as a phylum
*seven known orders/classes with many genera and species
*diversity in size, appearance, physiology, niches
*small like procholoroccus to large like Nostoc
Describe purple bacteria plygm
- all belong to proteobacteria
PSB
chromaticaceas: Chromatiumum + Thiodocossues that have S0 within cells
ectothiorhodospiracea: thiocytes, ectothiro that have S deposits outside the cells
PNSB
*dispered genera in Alphaprotecobactera + beta proteobacteria
Go through the criteria for PSB
Pigments: bacteriochlorophull-a or b
photosystems: 1
C source: CO2, carbon compounds
E- donor: H2S, S0 , H2, organic compounds
Aerobic dark growth: No
Go through criteria of PNSB
Pigments: bacteriophull a or b
Photosystems: 1
C source: organic compounds, CO2 sometimes
E- donor: H2, organic compounds
Aerobic dark growth: yes
Compare PS and PNSB (criteria too)
format: PS /// PNSB
main mode of photosynthesis: photoautotrophic /// photoheterophic
arobic growth: - /// +
oxidsing H2S: + /// +
S accumulation: + /// -
H2S toxicity: low /// high
Generally discuss Green bacteria
GSB:
*several genera in Chlorobiaceae in generally unknown Chlorobiota phylm
GNSB
*filamentous chloroflexi phyum
*several classes + genera
*filamentous, gliding, physiologically diverse
*relatively uncultured, mostly thermophiles
*aeorbe + anaerobe
*G+ but leaky so stains G-
Go through GSB criteria
Pigments: bacteriophyll c, d or e
Photosystems: 1
C source: CO2, organic compounds
E donor: H2S or So
Aerobic dark growth: No
Go through criteria for GNSB
pigments: bacteriophyl c, d or chlorophyll a
photosystem: 1
C source: organic compounds preffered but CO2 fixation also possible
E donor: sulfides
Aerobic dark growth: yes
What are heliobacteria
anoxygenic photoheteroptrophs
*Firmucutes, G+
*aneorbic, spire formers, N2 fixers
*DO NOT FIX CO2
Where do helicobacteria live, how possible
water logged soils, alkaine soils, soda lakes
- rice paddy soils
*rarely in aquatic habitats
*PSI has bacteriophyll g with unique absorbance spectrum = allows cells to colonise unique niches
Explain Photophosphorylation in Extreme Halophilic Archaea
- done by euryarchaeortes - halobacterium
*photophosphorylation not via electron flow
where bacteriorhodopsin acts as a light-driven proton pump, and only functions (for ATP synthesis) under anaerobic conditions
*NO CO2 fixation
remeber sc
REMEBER
What are PR
proteorhodspin widespread in marine bacteria, found in many taxa, associated with light driven proton pump
*2007 abundance was discovered via metagenomic sequencing
*found in alpha and gammaproteobacteria, which are both highly abundant
*also found in Cyanobacteria meaning organisms benefit from more than 1 type of phototrophy
What did the discovery of PR mean, unknowns?
- light driven proton pumps not limied to Archaea
*major source of energy for bacteria
*do not know if its linked to CO2 fixation, or how depth affects function
*not just limited to anaerobic extreme conditions like it is in archaea
Distinguish between Proteorhodopsin and Bacteriorhodopsin, comment on presence in euks
Proteorhodopsin: found in bacteria but is not limited to Proteobacteria
Bacteriorhodopsin: found only in extreme halophilic Archaea, not bacteria. Other homologues found in these Archaea include Archaerhodopsins
Similar rhodopsins also found in Eukaryotes i.e., green algae and
their viruses
