21: Bacterial Phototrophy

Question 1

Name characteristcs of bacterial phototrophs

Answer 1

1. cytoplasmic membrane infoldings via thylakoids in cyanobacteria, chromomes…
2. green/purple sulfur bacteria accumilate S0 intracellular or intracellularly
3. Green/purple NS bacteria may use sulfide as e- donors but not accumulate S0

Question 2

List phenotypic characteristics of bacterial phototrophs

Answer 2

Green bacteria are green or brown.

Purple bacteria can be yellow, orange, green, purple or red

Cyanobacteria can be green or blue

Question 3

What 5 criteria can you use to distinguish bacteria CPEAP

Answer 3

pigments, photosystems, C source, E donor, aeorbic dark growth

Question 4

Characterise Cyanobacteria using the five criteria

Answer 4

– 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

Question 5

Describe cyanoabacterium as a phylum

Answer 5

*seven known orders/classes with many genera and species
*diversity in size, appearance, physiology, niches
*small like procholoroccus to large like Nostoc

Question 6

Describe purple bacteria plygm

Answer 6

• 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

Question 7

Go through the criteria for PSB

Answer 7

Pigments: bacteriochlorophull-a or b

photosystems: 1

C source: CO2, carbon compounds

E- donor: H2S, S0 , H2, organic compounds

Aerobic dark growth: No

Question 8

Go through criteria of PNSB

Answer 8

Pigments: bacteriophull a or b

Photosystems: 1

C source: organic compounds, CO2 sometimes

E- donor: H2, organic compounds

Aerobic dark growth: yes

Question 9

Compare PS and PNSB (criteria too)

Answer 9

format: PS /// PNSB

main mode of photosynthesis: photoautotrophic /// photoheterophic

arobic growth: - /// +

oxidsing H2S: + /// +

S accumulation: + /// -

H2S toxicity: low /// high

Question 10

Generally discuss Green bacteria

Answer 10

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-

Question 11

Go through GSB criteria

Answer 11

Pigments: bacteriophyll c, d or e

Photosystems: 1

C source: CO2, organic compounds

E donor: H2S or So

Aerobic dark growth: No

Question 12

Go through criteria for GNSB

Answer 12

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

Question 13

What are heliobacteria

Answer 13

anoxygenic photoheteroptrophs

*Firmucutes, G+
*aneorbic, spire formers, N2 fixers
*DO NOT FIX CO2

Question 14

Where do helicobacteria live, how possible

Answer 14

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

Question 15

Explain Photophosphorylation in Extreme Halophilic Archaea

Answer 15

• 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

Question 16

remeber sc

Answer 16

REMEBER

Question 17

What are PR

Answer 17

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

Question 18

What did the discovery of PR mean, unknowns?

Answer 18

• 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

Question 19

Distinguish between Proteorhodopsin and Bacteriorhodopsin, comment on presence in euks

Answer 19

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