Limnohabitans planktonicus sp. nov. and Limnohabitans parvus sp. nov. two novel planktonic Betaproteobacteria isolated from a freshwater reservoir

摘要

Two strains II-B4^T and II-D5^T, isolated from the meso-eutrophic freshwater Římov Reservoir (Czech Republic) were phenotypic ally, phylogenetically and chemotaxonomically characterized. Both strains are chemoorganotrophic, facultatively anaerobic, rod-shaped, non-motiles with identical G+C contents of their DNA of 59.9 mol%. Their major polar lipids were diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine, and their major fatty acids were C16:1ω7c/C16:1ω6c, C16:0, C18:1ω7c/C18:1ω6c and C12:0. Both strains contained Q-8 as the only respiratory quinone component. The 16S rRNA sequences of the two strains posses a similarity of 99.0%, however the DNA-DNA reassociation value was only 26.7%, and the strains can be discriminated from each other by several chemotaxonomic and biochemical traits. The phylogenetic analysis of the 16S rRNA gene sequences revealed the affiliation of both strains with the genus Limnohabitans within the family Comamonadaceae. The two investigated strains represent a narrow phylogenetic cluster (so-called R-BT065 cluster) formed by a large number of environmental sequences obtained from the pelagic zones of various freshwater habitats. We propose to place the two strains in separate new species within the genus Limnohabitans. The two proposed species are Limnohabitans planktonicus sp. nov. with the type strain II-D5^T (= DSM 21594^T = CIP 109844^T), and Limnohabitans parvus sp. nov. with the type strain II-B4^T (= DSM 21592^T = CIP 109845^T).