Microbial diversity of the brine-seawater interface of the Kebrit Deep, Red Sea, studied via 16S rRNA gene sequences and cultivation methods

The brine-seawater interface of the Kebrit Deep, northern Red Sea, was inve stigated for the presence of microorganisms using phylogenetic analysis com bined with cultivation methods. Under strictly anaerobic culture conditions , novel halophiles were isolated. The ne,v rod-shaped isolates belong to th e halophilic genus Halanaerobium and are the first representatives of the g enus obtained from deep-sea, anaerobic brine pools. Within the genus Halana erobium, they represent new species which grow chemoorganotrophically at Na Cl concentrations ranging from 5 to 34%. The cellular fatty acid compositio ns are consistent with those of other Halanaerobium representatives, showin g unusually large amounts of Delta7 and Delta 11 16:1 fatty acids. Phylogen etic analysis of the brine-seawater interface sample revealed the presence of various bacterial 16S rRNA gene sequences dominated by cultivated member s of the bacterial domain, with the majority affiliated with the genus Hala naerobium. The new Halanaerobium 16S rRNA clone sequences showed the highes t similarity (99.9%) to the sequence of isolate KT-8-13 from the Kebrit Dee p brine. In this initial survey, our polyphasic approach demonstrates that novel halophiles thrive in the anaerobic, deep-sea brine pool of the Kebrit Deep, Red Sea. They may contribute significantly to the anaerobic degradat ion of organic matter enriched at the brine-seawater interface.