High phylogenetic diversity of Flavobacterium spp. isolated from a hardwater creek, Harz Mountains, Germany

Abstract Of 930 strains isolated on nutrient-poor media from water samples taken at four sites along a 370-m-long stretch of a hardwater creek, Westerhofer Bach, Harz Mountains, Germany, more than half had swarming capacity, many of which with slimy appearance. MALDI-TOF spectroscopic analysis of 60 randomly picked isolates grouped about 45% of them in different orders of Proteobacteria , while about 55% clustered with a representative of the genus Flavobacterium. The latter affiliation was supported by positive flexirubin reaction and fatty acid profiles performed on a subset of these isolates. Partial 16S rRNA gene sequence analysis of more than 100 swarming strains also supported the protein-based analysis, and suggested high phylogenetic diversity of the flavobacterial isolates at the intrageneric level. Phylogenetic analysis of almost complete gene sequences obtained for 41 strains and type strains of Flavobacterium species refined the phylogeny, allowing the conclusions that only some isolates are members of described species, and that the phylogenetic depth of the other lineages is indicative of the presence of about 20 novel Flavobacterium species, providing support by the polyphasic approach to systematics. The phylogenetic breadth and depth of diversity of Flavobacterium spp. in this creek are very similar to those in epilithon samples from the nutrient-rich River Taff in Cardiff (O’Sullivan, L.A., Rinna, J., Humphreys, G., Weightman, A.J., Fry, J.C., 2006. 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. Int. J. Syst. Evol. Microbiol. 56, 169–180.), prompting speculation about the rationale for this finding.