, Volume 181, Issue 1, pp 17-25
Date: 04 Dec 2003

Phylogenetic and physiological characterization of a filamentous anoxygenic photoautotrophic bacterium ‘Candidatus Chlorothrix halophila’ gen. nov., sp. nov., recovered from hypersaline microbial mats

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Abstract

We report the phylogenetic and physiological characterization of a mesophilic and halophilic member of the filamentous anoxygenic phototrophic (FAP) bacteria, provisionally named ‘Candidatus Chorothrix halophila’ gen. nov. sp. nov., that has been maintained in a highly enriched culture in our laboratory for over a decade. Phylogenetic analysis of small-subunit RNA-encoding sequences places ‘Candidatus Chlorothrix halophila’ in a clade that includes cultivated members of the genera Chloroflexus and Oscillochloris. Physiological studies demonstrated sulfide-dependent photosynthetic uptake of 14C-labeled bicarbonate. Enzymatic assays for the activity of propionyl-coenzyme A synthase indicated that ‘Candidatus Chlorothrix halophila’ does not use the 3-hydroxypropionate cycle of Chloroflexus aurantiacus OK-70-fl for autotrophic carbon assimilation. New concepts regarding the taxonomy and phylogeny of FAP bacteria have emerged from this work.