Chlorobaculum tepidum

Chlorobaculum tepidum, previously known as Chlorobium tepidum,[1] is an anaerobic, thermophilic green sulfur bacteria first isolated from New Zealand.[2] Its cells are gram-negative and non-motile rods of variable length. They contain chlorosomes [3] and bacteriochlorophyll a and c.[4]

Chlorobaculum tepidum
Scientific classification
Domain:
Bacteria
Phylum:
Chlorobiota
Class:
"Chlorobia"
Order:
Chlorobiales
Family:
Chlorobiaceae
Genus:
Chlorobaculum
Species:
C. tepidum
Binomial name
Chlorobaculum tepidum
(Wahlund et al. 1996) Imhoff 2003
Synonyms

Chlorobium tepidum Wahlund et al. 1996

Natural habitat and environmental requirements

Like other green sulfur bacteria C. tepidum requires light and specific compounds to perform anoxygenic photosynthesis.[3] The compounds that C. tepidum requires reduced sulfur compounds (H2S, S0, thiosulfate), hydrogen gas (H2,) or ferrous iron (Fe2+).[5] To fulfill their metabolic requirements, they reside primarily in anaerobic sulfur rich environments such as anaerobic levels of stratified lakes and lagoons, anaerobic levels of layered organic bacterial mats, and in hot springs where there is abundant sulfur.[5] C. tepidum and other green sulfur bacteria also play a large role within the carbon and sulfur cycles.[5] Within the sulfur cycle, they contribute to the oxidative branch by oxidizing reduced sulfur compounds.[6] Within anaerobic sediment layers C. tepidum is able to couple carbon and sulfur cycling in a metabolically favorable way.[6]

Photosynthetic mechanism

As it was mentioned before, C. tepidum performs anoxygenic photosynthesis. Within each cell there are 200-250 chlorosomes[3] that are attached to the cytoplasmic side of reaction centers inserted within the inner cell membrane.[3] The ellipsoidal shaped complexes act as light harvesting antenna to capture energy.[3] Within each chlorosome are 215,000 ± 80,000 bacteriochlorophyll C[4] that act as pigment molecules and absorb unique wavelengths of light relative to their color.[4] Light energy is harvested by the chlorosomes and used in conjunction with H2, reduced sulfur compounds, or ferrous iron to preform redox reactions and provide energy to fix CO2 via the reverse tricarboxcylic acid cycle.[7]

Genome structure

C. tepidum contains a genome that contains 2.15 Mbp, within there are a total of 2,337 genes (of these genes, there are 2,245 protein coding genes and 56 tRNA and rRNA coding genes).[8] It's synthesis of chlorophyll a and bacteriochlorophylls a and c make it a model organism used to elucidate the biosynthesis of bacteriochlorophylls c.[9] Several of its carotenoid metabolic pathways (including a novel lycopene cyclase) have similar counterparts in cyanobacteria.[10][11]

See also

References
  1. Imhoff, Johannes (2003). "Phylogenetic taxonomy of the family Chlorobiaceae on the basis of 16S rRNA and fmo (Fenna– Matthews–Olson protein) gene sequences" (PDF). International Journal of Systematic and Evolutionary Microbiology. 53 (Pt 4): 941–951. doi:10.1099/ijs.0.02403-0. PMID 12892110.
  2. Wahlund, Thomas M.; Woese, Carl R.; Castenholz, Richard W.; Madigan, Michael T. (1991). "A thermophilic green sulfur bacterium from New Zealand hot springs, Chlorobium tepidum sp. nov". Archives of Microbiology. 156 (2): 81–90. doi:10.1007/BF00290978. ISSN 0302-8933. S2CID 22133132.
  3. Frigaard, Niels-Ulrik; Chew, Aline Gomez Maqueo; Li, Hui; Maresca, Julia A.; Bryant, Donald A. (2003). "Chlorobium Tepidum : Insights into the Structure, Physiology, and Metabolism of a Green Sulfur Bacterium Derived from the Complete Genome Sequence". Photosynthesis Research. 78 (2): 93–117. doi:10.1023/B:PRES.0000004310.96189.b4. ISSN 0166-8595. PMID 16245042. S2CID 30218833.
  4. Montano, Gabriel A.; Bowen, Benjamin P.; LaBelle, Jeffrey T.; Woodbury, Neal W.; al, et (October 2003). "Characterization of Chlorobium tepidum chlorosomes: A calculation of bacteriochlorophyll c per chlorosome and oligomer modeling". Biophysical Journal. 85 (4): 2560–2565. doi:10.1016/S0006-3495(03)74678-5. PMC 1303479. PMID 14507718. ProQuest 215720771.
  5. Li, Hui; Jubelirer, Sara; Garcia Costas, Amaya M.; Frigaard, Niels-Ulrik; Bryant, Donald A. (2009). "Multiple antioxidant proteins protect Chlorobaculum tepidum against oxygen and reactive oxygen species". Archives of Microbiology. 191 (11): 853–867. doi:10.1007/s00203-009-0514-7. ISSN 0302-8933. PMID 19784828. S2CID 8881227.
  6. Rodriguez, Jesse; Hiras, Jennifer; Hanson, Thomas E. (2011). "Sulfite Oxidation in Chlorobaculum Tepidum". Frontiers in Microbiology. 2: 112. doi:10.3389/fmicb.2011.00112. ISSN 1664-302X. PMC 3119408. PMID 21747809.
  7. Frigaard, Niels-Ulrik; Chew, Aline Gomez Maqueo; Li, Hui; Maresca, Julia A.; Bryant, Donald A. (2003). "Chlorobium Tepidum : Insights into the Structure, Physiology, and Metabolism of a Green Sulfur Bacterium Derived from the Complete Genome Sequence". Photosynthesis Research. 78 (2): 93–117. doi:10.1023/B:PRES.0000004310.96189.b4. ISSN 0166-8595. PMID 16245042. S2CID 30218833.
  8. Eisen JA, Nelson KE, Paulsen IT, et al. (July 2002). "The complete genome sequence of Chlorobium tepidum TLS, a photosynthetic, anaerobic, green-sulfur bacterium". Proceedings of the National Academy of Sciences of the United States of America. 99 (14): 9509–14. Bibcode:2002PNAS...99.9509E. doi:10.1073/pnas.132181499. PMC 123171. PMID 12093901.
  9. N.-U. Frigaard; et al. (2006). B. Grimm; et al. (eds.). Chlorophylls and Bacteriochlorophylls: Biochemistry, Biophysics, Functions and Applications. Vol. 25. Springer. 201–221.
  10. N.-U. Frigaard; et al. (2004). "Genetic manipulation of carotenoid biosynthesis in the green sulfur bacterium Chlorobium tepidum". Journal of Bacteriology. 186 (16): 5210–5220. doi:10.1128/jb.186.16.5210-5220.2004. PMC 490927. PMID 15292122.
  11. J.A. Maresca; et al. (2005). A. van der Est; D. Bruce (eds.). Photosynthesis: Fundamental Aspects to Global Perspectives. Allen Press. pp. 884–886.

Further reading
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