Culturable phylogenetic diversity of the phylum 'Bacteroidetes' from river epilithon and coastal water and description of novel members of the family Flavobacteriaceae: Epilithonimonas tenax gen. nov., sp. nov. and Persicivirga xylanidelens gen. nov., sp. nov.

Members of the phylum 'Bacteroidetes' are important heterotrophs involved in cycling organic carbon in aquatic habitats. Their diversity has been studied by molecular methods in both freshwater and marine habitats and many novel genera and species within this phylum have been characterized in recent years. In this study, we examined the diversity of members of the 'Bacteroidetes' that could be readily isolated on solid media from river epilithon and coastal sea water. Most (93 %) of the 55 isolates confirmed as members of the 'Bacteroidetes' and examined by phylogenetic analysis of 16S rRNA gene sequences belonged to the Flavobacteriaceae. Furthermore, most (62 %) of these were almost certainly members of the genus Flavobacterium and all but one were from river epilithon. Conversely, the sea-water isolates were more widely distributed in clades containing other genera. Some of the isolates were deep-branching within phylogenetic trees and so could not be assigned to putative genera. Two of these deep-branching isolates were characterized by polyphasic taxonomy and are proposed as novel species within two new genera of the family Flavobacteriaceae. These are Epilithonimonas tenax gen. nov., sp. nov. (type strain EP105T = NCIMB 14026T = DSM 16811T) and Persicivirga xylanidelens gen. nov., sp. nov. (type strain SW256T = NCIMB 14027T = DSM 16809T).