Roseiflexus castenholzii explained

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] R. castenholzii was first isolated from red-colored bacterial mats located Nakabusa hot springs in Japan. Because this organism is a phototroph, it utilizes photosynthesis to fix carbon dioxide and build biomolecules. R. castenholzii has three photosynthetic complexes: light-harvesting only, reaction center only, and light-harvesting with reaction center.

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.^[3] R. castenholzii lacks internal vesicles, internal membranes, and complex structures. This species has gliding motility.

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. 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. 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. 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.

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).

Photosynthesis

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

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. The majority of these pigments are bacteriochlorophyll (BChl). 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. The RC also contains BChl and bacteriopheophytin (BPhe) pigments.^[6]

Further reading

• Tsukatani Y, Nakayama N, Shimada K, Mino H, Itoh S, Matsuura K, Hanada S, Nagashima KV . 6 . Characterization of a blue-copper protein, auracyanin, of the filamentous anoxygenic phototrophic bacterium Roseiflexus castenholzii . Archives of Biochemistry and Biophysics . 490 . 1 . 57–62 . October 2009 . 19683508 . 10.1016/j.abb.2009.08.003 .
• van ver Meer MT, Schouten S, Hanada S, Hopmans EC, Damsté JS, Ward DM . 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 . September 2002 . 12189424 . 10.1007/s00203-002-0449-8 . 20209263 .
• Xin Y, Pan J, Collins AM, Lin S, Blankenship RE . Excitation energy transfer and trapping dynamics in the core complex of the filamentous photosynthetic bacterium Roseiflexus castenholzii . Photosynthesis Research . 111 . 1–2 . 149–156 . March 2012 . 21792612 . 10.1007/s11120-011-9669-6 . 17430575 .

External links

• Propagation of LexA regulog to Roseiflexus castenholzii DSM 13941
• Type strain of Roseiflexus castenholzii at BacDive - the Bacterial Diversity Metadatabase

Notes and References

1. Hanada S, Takaichi S, Matsuura K, Nakamura K . 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 . January 2002 . 11837302 . 10.1099/00207713-52-1-187 . free .
2. Book: Hanada S, Pierson BK . The Family Chloroflexaceae . 2006 . The Prokaryotes . 815–842 . Dworkin M, Falkow S, Rosenberg E, Schleifer KH . New York, NY . Springer New York . en . 10.1007/0-387-30747-8_33 . 978-0-387-25497-5 .
3. Book: The prokaryotes. Vol. 7. Proteobacteria : delta and epsilon subclasses, deeply rooting bacteria : a handbook on the biology of bacteria . 2006 . Springer . Dworkin M, Falkow S . 978-0-387-30747-3 . 3rd . New York . 262687432.
4. Collins AM, Qian P, Tang Q, Bocian DF, Hunter CN, Blankenship RE . Light-harvesting antenna system from the phototrophic bacterium Roseiflexus castenholzii . Biochemistry . 49 . 35 . 7524–7531 . September 2010 . 20672862 . 10.1021/bi101036t .
5. Collins AM, Xin Y, Blankenship RE . Pigment organization in the photosynthetic apparatus of Roseiflexus castenholzii . Biochimica et Biophysica Acta (BBA) - Bioenergetics . 1787 . 8 . 1050–1056 . August 2009 . 19272352 . 10.1016/j.bbabio.2009.02.027 .
6. Yamada M, Zhang H, Hanada S, Nagashima KV, Shimada K, Matsuura K . 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 . March 2005 . 15716441 . 1063993 . 10.1128/JB.187.5.1702-1709.2005 .