Roseiflexus castenholzii

Roseiflexus castenholzii is a heterotrophic, thermophilic, filamentous anoxygenetic phototroph (FAP) bacterium.[1] This species is in one of two genera of FAPs that lack chlorosomes.[2][3] R. castenholzii was first isolated from red-colored bacterial mats located Nakabusa hot springs in Japan.[1] Because this organism is a phototroph, it utilizes photosynthesis to fix carbon dioxide and build biomolecules. R. castenholzii has three photosynthetic complexes: light-harvesting, reaction center, and light-harvesting - reaction center.[4]

Roseiflexus castenholzii
Scientific classification Edit this classification
Domain: Bacteria
Phylum: Chloroflexota
Class: Chloroflexia
Order: Chloroflexales
Family: Roseiflexaceae
Genus: Roseiflexus
Species:
R. castenholzii
Binomial name
Roseiflexus castenholzii
Hanada et al., 2002

Morphology

This bacterium has a cell diameter is of 0.8-1.0 micrometers but does not have a definite length because of its multicelluar filamentous structure. The bacterium is red to reddish-brown forms distinct red bacterial mats in the natural environment.[2] R. castenholzii lacks internal vesicles, internal membranes, and complex structures. This species has gliding motility.[1]

Phylogeny

The five currently known genera of FAP organisms are Chlorofelxus, Choronema, Oscillochloris, Roseiflexus, and Heliothrix. Of these five, only two do not contain chlorosomes: Roseiflexus and Heliothrix.[3] Roseiflexus and Heliothrix are both red due to only having Bchl a as a photosyntheic pigment. In most other aspects, both phenotypically and genetically, the genera Roseiflexus and Heliothrix are different from each other.[3] Little is known about the taxonomy of the Roseiflexus genus due to it only containing one known species: Roseiflexus casternholzii.

Habitat

When first discovered, Roseiflexus castenholzii was isolated from the lowest layer of a three layered bacterial mat; the top two layers contained cyanobacteria and Chloroflexus spp.[3] These mats were found in multiple Japanese hot springs ranging in temperature from 45.5 °C to 68.5 °C and with a neutral to alkaline pH range.[1][3]

This bacterium is able to grow photoheterotrophically under anaerobic light conditions and chemoheterotrophically under aerobic dark conditions. Optimal growth conditions for this organism are 50 °C and pH 7.5-8.0. The first isolated type strain was HLO8T (= DSM 13941T = JCM 11240T).[1][2]

Photosynthesis

In order to conduct photosynthesis, Roseiflexus castenholzii contains light-harvesting - reaction center (LHRC), light-harvesting (LH) only, and reaction center (RC) only complexes.[4] In contrast to most other FAPs, R. castenholzii does not have chlorosomes, which contain great amounts of photosynthetic pigments.[4] Because chlorosomes can obstruct observations of photosynthetic complexes, Roseiflexus castenholzii is considered a model organism to study the reaction centers FAPs have.[4]

The LHRC contains both light harvesting and reaction center peptides that allow for absorbing light and exciting electrons in one complex.[5] The light-harvesting complex contains antenna pigments that allow the bacterium to absorb light around 800 nanometers.[5] The majority of these pigments are bacteriochlorophyll (BChl).[4] The reaction center in Roseiflexus castenholzii is closely related to the RC of Chloroflexus aurantiacus. R. castenholzii's RC complex contains three subunits: L, M, and a c-type cytochrome. It lacks the H subunit common in purple bacteria.[5] The RC also contains BChl and bacteriopheophytin (BPhe) pigments.[6][4]

References
  1. Hanada S, Takaichi S, Matsuura K, Nakamura K (January 2002). "Roseiflexus castenholzii gen. nov., sp. nov., a thermophilic, filamentous, photosynthetic bacterium that lacks chlorosomes". International Journal of Systematic and Evolutionary Microbiology. 52 (Pt 1): 187–193. doi:10.1099/00207713-52-1-187. PMID 11837302.
  2. Dworkin M, Falkow S (2006). The prokaryotes. Vol. 7. Proteobacteria : delta and epsilon subclasses, deeply rooting bacteria : a handbook on the biology of bacteria (3rd ed.). New York: Springer. ISBN 978-0-387-30747-3. OCLC 262687432.
  3. Hanada S, Pierson BK (2006). "The Family Chloroflexaceae". In Dworkin M, Falkow S, Rosenberg E, Schleifer KH (eds.). The Prokaryotes. New York, NY: Springer New York. pp. 815–842. doi:10.1007/0-387-30747-8_33. ISBN 978-0-387-25497-5.
  4. Collins AM, Qian P, Tang Q, Bocian DF, Hunter CN, Blankenship RE (September 2010). "Light-harvesting antenna system from the phototrophic bacterium Roseiflexus castenholzii". Biochemistry. 49 (35): 7524–7531. doi:10.1021/bi101036t. PMID 20672862.
  5. Collins AM, Xin Y, Blankenship RE (August 2009). "Pigment organization in the photosynthetic apparatus of Roseiflexus castenholzii". Biochimica et Biophysica Acta (BBA) - Bioenergetics. 1787 (8): 1050–1056. doi:10.1016/j.bbabio.2009.02.027. PMID 19272352.
  6. Yamada M, Zhang H, Hanada S, Nagashima KV, Shimada K, Matsuura K (March 2005). "Structural and spectroscopic properties of a reaction center complex from the chlorosome-lacking filamentous anoxygenic phototrophic bacterium Roseiflexus castenholzii". Journal of Bacteriology. 187 (5): 1702–1709. doi:10.1128/JB.187.5.1702-1709.2005. PMC 1063993. PMID 15716441.

Further reading
  • Tsukatani Y, Nakayama N, Shimada K, Mino H, Itoh S, Matsuura K, et al. (October 2009). "Characterization of a blue-copper protein, auracyanin, of the filamentous anoxygenic phototrophic bacterium Roseiflexus castenholzii". Archives of Biochemistry and Biophysics. 490 (1): 57–62. doi:10.1016/j.abb.2009.08.003. PMID 19683508.
  • van ver Meer MT, Schouten S, Hanada S, Hopmans EC, Damsté JS, Ward DM (September 2002). "Alkane-1,2-diol-based glycosides and fatty glycosides and wax esters in Roseiflexus castenholzii and hot spring microbial mats". Archives of Microbiology. 178 (3): 229–237. doi:10.1007/s00203-002-0449-8. PMID 12189424. S2CID 20209263.
  • Xin Y, Pan J, Collins AM, Lin S, Blankenship RE (March 2012). "Excitation energy transfer and trapping dynamics in the core complex of the filamentous photosynthetic bacterium Roseiflexus castenholzii". Photosynthesis Research. 111 (1–2): 149–156. doi:10.1007/s11120-011-9669-6. PMID 21792612. S2CID 17430575.
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