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Green Sulfur Bacteria
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Green Sulfur Bacteria (Chlorobiaceae)
by: Mirelise, Ikeya, Bola and Cynthia
classification
- Green sulfur bacteria (the family Chlorobiaceae) are anoxygenic phototrophic bacteria that grow only under strictly anoxic conditions.
- mainly use sulfide ions as electron donors.
-Green sulfur bacteria such as Chlorobium tepidum and Chlorobium vibrioforme belong to the phyla Chlorobi and are strictly anaerobic photoautotrophs.
classifications.
anoxygenic Photosynthesis
- Anoxygenic photosynthesis bacteria consume Co2, light energy to create organic compounds, sulfur or fumarate compounds instead of O2
- it uses bacteriochlorophyll instead of chlorophyll and involves one photosystem (PS I) to generate ATP in "Cyclic manner)
Purple and green sulfur bacteria are commonly found in microbial mats and stratified water columns. Anoxygenic CO2 fixation impacts the pH in a similar manner as the oxygenic counterpart, with the difference being that HS− oxidation decreases alkalinity:
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-The overall effect is that during anoxygenic photosynthesis, 0.5 mol of CaCO3 precipitates per mole of CO2 fixed.
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Habitat
habitat
-Green sulfur bacteria have been found in depths of up to 145m in the Black Sea, with low light availability.
-sulfur-rich environments
They employ a unique antenna complex termed the chlorosome, which comprises BChl c, BChl d, and BChl e. It is the largest known antenna structure in biology, with each chlorosome containing ∼200 000 BChl molecules. The habitats of green sulfur bacteria necessitate such an extensive antenna system, requiring a very large optical cross section to capture the few available photons. The light energy is transferred to a homodimeric Type I reaction center via the BChl a containing the Fenna–Matthews–Olsen (FMO) protein.
Reproduction
Reproduction
Green sulfur bacteria do not reproduce because they are photoautotrophs. This means they don't need other organisms and use the sun and photosynthesis and essentially form into glucose. This glucose is what gives them energy and allows them to stay alive.
Photosynthesis
Photosynthesis
This bacteria is anaerobic photoautotrophs. They are said to be "NADH" generated and live in "low intensities". On their own they are able to produce carbon fixation
Natural Enemies
Green sulfur bacteria does not have a specific enemy besides certain places where its conditions grow. Because they are photoautotrophs, they need "terrestrial enviornments" which will allow them to grow and further more their photosynthesis.
Natural enemies
Charts
chart
photosynthetic apparatus
The photosynthetic unit comprises of the chlorosome containing the BChls encased in a monolipid-protein envelope, the Fenna–Matthews–Olson (FMO) protein and a reaction center (RC) complex. Proteins involved in chlorosome and envelop formation include CsmA, B, C, D, E, F, H, I, J and X. The BChls c, d or e are represented as rodlike structures absorbing light energy that gets funneled to the RC via the baseplate and FMO. The FMO protein is part of the photosynthetic apparatus and is organized as trimers and binds to BChl a in the baseplate. The FMO and baseplate mediates the transfer of energy between the chlorosome and RC, which is found in the inner membrane. The core RC of the complex is composed of two copies of integral membrane proteins, PscA and one copy of the peripheral protein PscB, which carries the FeS centers. Two copies of PscC cytochrome c proteins and one copy of PscD make up the rest of the RC complex. Proteins identified in the metaproteome are shown in bold.
-Tricarboxylic acid (TCA) cycle. Partial oxidative and complete reductive TCA cycles in C-Ace.
TCA
-TCA cycle is operating in both the reductive and the oxidative directions, for carbon fixation and ammonia assimilation
Sulfur cycle for C-Ace and sulfate-reducing bacteria (SRB) within Ace Lake. Sulfide in the form of H2S is generated by the community of SRB residing in the anoxic zone of the lake (below 12.7 m). The exchange of sulfur between the green sulfur bacteria (GSB) and SRB is shown in the inset. During summer, the thick zone of C-Ace just below the chemocline (12 m) oxidizes the sulfide produced from the SRB to sulfate. Sulfate then diffuses to neighboring SRB in the zone and down the water column, whereupon it is reduced back to sulfide. The extent of light penetration in summer versus winter is shown, with phototrophic energy generation and cell growth occurring during the summer months. Enzymes identified in the metaproteome are shown in the inset.
SULFUR
CYCLING
Description
Description Of Green Sulfur Bacteria
- This bacteria in particular depends on light for life due to their phototrophic metabolism.
- It produces a highly efficient photosynthesis due to presence of light harvesting organelles and chlorosomes, which are filled with bacteriochlorophyll molecules.
- They inhabit the lowest part of the photic environments due to their constant light capture.
- Green sulfur bacteria inhabit the lowermost part of the chemocline in the stratified environment due to sensitivity to oxygen and have high sulfide tolerance depending on the light.
Ecological Importance
Ecological Importance
The ecological importance of green sulfur bacteria is their potential to oxidize H2S to sulfate under anaerobic conditions. They assimilate carbon dioxide into cell materias and is the electron acceptor of the oxidation process. While its under H2S the anaerobic conditions reduce bacteria and is achieved without the consumption of molecular oxygen.
uniqueness
Green sulfur bacteria have gained much attention because of a number of highly interesting features including unique structures of the photosynthetic apparatus and the presence of chlorosomes as very powerful light antenna that can capture minute amounts of light.This has important ecological consequences, because the efficient light‐harvesting determines the ecological niche of these bacteria at the lowermost part of stratified environments where the least of light is available. Furthermore, the strict dependency on photosynthesis to provide energy for growth and the obligate phototrophy of green sulfur bacteria together with their characteristic sulfur metabolism have provoked much interest in their physiology, ecology and genomics. The oxidation of sulfide as their outmost important photosynthetic electron donor involves the deposition of elemental sulfur globules outside the cells and separates the process of sulfide oxidation to sulfate into two parts. This is the basis for stable syntrophic associations between green sulfur bacteria and sulfur‐ and sulfate‐reducing bacteria in which the sulfur compounds are recycled. The green sulfur bacteria are distantly related to other bacteria and represent the phylum Chlorobi, though the known representatives are taxonomically treated as Chlorobiaceae with the genera Chlorobium, Chlorobaculum, Prosthecochloris and Chloroherpeton.
CITATIONS
- https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/green-sulfur-bacteria#:~:text=They%20are%20found%20mostly%20in,lakes%20and%20in%20marine%20habitats.
CITATIONS
- https://www.sciencedirect.com/topics/medicine-and-dentistry/green-sulfur-bacteria
- https://biologydictionary.net/photoautotroph/
-https://www.nature.com/articles/ismej201028
-https://onlinelibrary.wiley.com/doi/abs/10.1002/9780470015902.a0000458.pub2#:~:text=Green%20sulfur%20bacteria%20have%20gained,capture%20minute%20amounts%20of%20light.