Phylogeny and molecular fingerprinting of green sulfur bacteria
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© Springer-Verlag 1997
O R I G I N A L PA P E R
Jörg Overmann · Christian Tuschak
Phylogeny and molecular fingerprinting of green sulfur bacteria
Received: 26 August 1996 / Accepted: 8 January 1997
Abstract The 16S rDNA sequences of nine strains of green sulfur bacteria (Chlorobiaceae) were determined and compared to the four known sequences of Chlorobiaceae and to sequences representative for all eubacterial phyla. The sequences of the Chlorobiaceae strains were consistent with the secondary structure model proposed earlier for Chlorobium vibrioforme strain 6030. Similarity values > 90.1% and Knuc values < 0.11 indicate a close phylogenetic relatedness among the green sulfur bacteria. As a group, these bacteria represent an isolated branch within the eubacterial radiation. In Chlorobiaceae, a similar morphology does not always reflect a close phylogenetic relatedness. While ternary fission is a morphological trait of phylogenetic significance, gas vesicle formation occurs also in distantly related species. Pigment composition is not an indicator of phylogenetic relatedness since very closely related species contain different bacteriochlorophylls and carotenoids. Two different molecular fingerprinting techniques for the rapid differentiation of Chlorobiaceae species were investigated. The 16S rDNA fragments of several species could not be separated by denaturing gradient gel electrophoresis. In contrast, all strains investigated during the present work gave distinct banding patterns when dispersed repetitive DNA sequences were used as targets in PCR. The latter technique is, therefore, well suited for the rapid screening of isolated pure cultures of green sulfur bacteria. Key words Green sulfur bacteria · Chlorobiaceae · DNA sequences · Ribosomal RNA · Phylogeny · Taxonomy Abbreviations Bac Bacteroides, Cfl Chloroflexus, Chl Chlorobium, Chp Chloroherpeton, Chr Chromatium,
J. Overmann (Y) · C. Tuschak Paläomikrobiologie, Institut für Chemie und Biologie des Meeres, Postfach 2503, D-26111 Oldenburg, Germany Tel. +49-441-970-6376; Fax +49-441-798-3583 e-mail [email protected]
Clt Clathrochloris, Cyt Cytophaga, Dei Deinococcus, Pld Pelodictyon, Ptc Prosthecochloris, Rsp Rhodospirillum, Spi Spirochaeta, Bchl bacteriochlorophyll, DGGE Denaturing gradient gel electrophoresis, ERIC Enterobacterial repetitive intergenic consensus, Env. Environmental 16S rRNA gene
Introduction Green sulfur bacteria are anoxygenic, photosynthetic eubacteria that grow only under strictly anoxic conditions. They form characteristic light-harvesting structures (called chlorosomes) and specific antenna pigments (bacteriochlorophylls c, d, or e). These features distinguish them from all other groups of phototrophic bacteria. Currently, green sulfur bacteria are divided into six genera and 15 species (Witt et al. 1989; Imhoff 1995). The physiological capacities of green sulfur bacteria are too similar to permit a differentiation between the taxa since only a few organic carbon substrates (mainly acetate, pyruvate, and
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