Diversity and distribution in hypersaline microbial mats of bacteria related to Chloroflexus spp.

Filamentous bacteria containing bacteriochlorophylls c and a were enriched from hypersaline microbial mats. Based on phylogenetic analyses of 16S rRNA gene sequences, these organisms form a previously undescribed lineage dist antly related to Chloroflexus spp. We developed and tested a set of PCR pri mers for the specific amplification of 16S rRNA genes from filamentous phot otrophic bacteria within the kingdom of "green nonsulfur bacteria." PCR pro ducts recovered from microbial mats in a saltern in Guerrero Negro, Mexico, were subjected to cloning or denaturing gradient gel electrophoresis and t hen sequenced. We found evidence of a high diversity of bacteria related to Chloroflexus which exhibit different distributions along a gradient of sal inity from 5.5 to 16%.