The phylogenetic relationships of Chlorobium tepidum and Chloroflexus aurantiacus based upon their RecA sequences

Tanja M. Gruber, Jonathan A. Eisen, Kurt Gish, Donald A. Bryant

Abstract: Using RecA as the phylogenetic marker, the relationships of the green sulfur bacterium Chlorobium tepidum and the green gliding bacterium Chloroflexus aurantiacus to other eubacteria were investigated. The recA genes of the two organisms were cloned, and the resulting protein sequences aligned with 86 other eubacterial RecA sequences. Cb. tepidum was placed as the nearest relative to the Cytophaga/ Flexibacter/Bacteroides group, a relationship supported by results obtained with several phylogenetic markers. Cf. aurantiacus was placed near Chlamydia trachomatis and the high-GC gram-positives; however, this placement was not strongly supported statistically. Possible reasons for this ambiguity are discussed.

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