Anoxygenic phototrophy across the phylogenetic spectrum: current understanding and future perspectives |
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Authors: | E Stackebrandt Frederick A Rainey Naomi Ward-Rainey |
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Institution: | (1) DSMZ-Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH, Mascheroder Weg 1B, D-38124 Braunschweig, Germany Tel. +49-531-2616-352; Fax +49-531-2616-418 e-mail: erko@gbf-braunschweig.de, DE |
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Abstract: | The phylogenetic heterogeneity of anoxygenic phototrophic bacteria has been revealed by 16S rRNA sequence analysis, the results
of which have led to extensive taxonomic rearrangements within previously defined taxa of phototrophs and stimulated interest
in this group of organisms. Anoxygenic photosynthetic bacteria can be found within 4 of the 12 phylogenetic lineages, and
in some cases are highly related to non-photosynthetic members of these groups. The largest number of phototrophs are found
in the class Proteobacteria. Comparative phylogenetic analysis using 23S rDNA sequences generally supports the topology obtained
from 16S rDNA sequences. The photosynthetic reaction centers are conserved in all photosynthetic bacteria, and are of two
types. One is shared by the Proteobacteria and Chloroflexus aurantiacus and is similar to Photosystem II of cyanobacteria, while heliobacteria and Chlorobium and relatives possess a reaction center similar to the cyanobacterial Photosystem I. These similarities are supported by
sequence analysis of core reaction center peptides, but contradict phylogenies reconstructed from rRNA sequence analysis.
Genome analysis by means of physical mapping has been performed for only three species of anoxygenic phototrophs. Some conservation
of operon structure and gene sequence has been found within the Proteobacteria, but does not extend to other phototrophs.
Received: 29 December 1995 / Accepted: 19 July 1996 |
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Keywords: | Anoxygenic phototrophs rRNA rDNA Phylogenetic relationships Reaction center Gene transfer Genome analysis |
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