RT Journal Article SR Electronic(1) A1 Hahn, Martin W. A1 Minasyan, Arevik A1 Lang, Elke A1 Koll, Ulrike A1 Spröer, CatrinYR 2012 T1 Polynucleobacter difficilis sp. nov., a planktonic freshwater bacterium affiliated with subcluster B1 of the genus Polynucleobacter JF International Journal of Systematic and Evolutionary Microbiology, VO 62 IS 2 SP 376 OP 383 DO https://doi.org/10.1099/ijs.0.031393-0 PB Microbiology Society, SN 1466-5034, AB Strain AM-8B5T, isolated from Lake Sevan in Armenia, was characterized phenotypically, chemotaxonomically and phylogenetically. This chemo-organoheterotrophic, aerobic, facultatively anaerobic, catalase- and oxidase-positive, non-motile strain grew on NSY medium at NaCl concentrations of 0.0–0.2 % (w/v) and at 4–30 °C. Whole-cell fatty acids were dominated by summed feature 3 (including C16 : 1ω7c and iso-C15 : 0 2-OH), C16 : 0 and C18 : 1ω7c. C12 : 0 2-OH and C16 : 1 2-OH were the only hydroxylated fatty acids detected. Phylogenetic analysis as well as phenotypic and chemotaxonomic similarities indicated that the novel isolate was affiliated with the genus Polynucleobacter. 16S rRNA gene similarity values with the four previously described Polynucleobacter species ranged from 96.2 to 98.7 %. DNA–DNA hybridization experiments showed that the isolate did not belong to any of the previously described Polynucleobacter species. The isolate could be distinguished from all previously established Polynucleobacter species based on chemotaxonomic and phenotypic traits. The bacterium possessed a free-living lifestyle and represents a group of bacteria inhabiting the water column of many freshwater lakes. Based on the revealed phylogeny, and chemotaxonomic and phenotypic differences to previously described Polynucleobacter species, it is proposed that the isolate represents a novel species, Polynucleobacter difficilis sp. nov.; the type strain is AM-8B5T ( = DSM 22349T = CIP 110078T)., UL https://www.microbiologyresearch.org/content/journal/ijsem/10.1099/ijs.0.031393-0