Shewanella arctica sp. nov., an iron-reducing bacterium isolated from Arctic marine sediment.

Two strains of dissimilatory iron-reducing bacteria, which could couple lactate oxidation to iron reduction for energy conservation, were isolated from Arctic marine sediment. The strains, IR12(T) and IR26, were both Gram-staining-negative, catalase- and oxidase-positive and facultative anaerobes. Their cells were rod-shaped and motile by means of a polar flagellum. Both strains grew in the presence of 0.5-3.5 % (w/v) NaCl, with an absolute requirement for Na(+). Both were psychrotolerant since they could grow at 4-28 °C but had an optimum growth temperature of 20 °C. Both grew at pH 4.5-9.0 (optimum, pH 7.5). The major fatty acids of strains IR12(T) and IR26 were summed feature 3 (C(16 : 1)ω6c and/or C(16 : 1)ω7c) and C(16 : 0). Phylogenetic analyses based on 16S rRNA gene sequences indicated that strains IR12(T) and IR26 belonged to the class Gammaproteobacteria and were most closely related to Shewanella vesiculosa M7(T), Shewanella livingstonensis NF22(T) and Shewanella frigidimarina ACAM 591(T) (with 98.5 and 98.8 %, 98.5 and 98.8 %, and 98.5 and 98.8 % sequence similarities, respectively). The genomic DNA G+C contents of strains IR12(T) and IR26 were 40.0 and 40.3 mol%, respectively. DNA-DNA relatedness data indicated that the two novel strains represented a single species that was distinct from S. vesiculosa M7(T), S. livingstonensis NF22(T) and S. frigidimarina ACAM 591(T). Based on the phylogenetic, phenotypic and DNA-DNA relatedness data, the two new strains represent a single novel species of the genus Shewanella, for which the name Shewanella arctica sp. nov. is proposed. The type strain is IR12(T) ( = KCTC 23109(T) = JCM 16723(T)).

Phenylobacterium muchangponense sp. nov., isolated from beach soil, and emended description of the genus Phenylobacterium.

A Gram-staining-negative, non-motile, aerobic bacterium, designated strain A8T, was isolated from the beach soil of Muchangpo, Korea. Cells were rod-shaped (0.5-0.6×0.7-1.3 µm) and colonies were colourless, circular with entire edges and had a glistening surface. The isolate grew optimally at 25-35 °C and did not require NaCl for growth. Strain A8T could not assimilate acetate, DL-lactate, succinate, antipyrine or chloridazon, but weakly assimilated L-phenylalanine. Major fatty acids were summed feature 7 (comprising C18:1ω7c/ω9t/ω12t), C16:0 and summed feature 4 (comprising C16:1ω7c/ iso-C15:0 2-OH). The major isoprenoid quinone was ubiquinone-10 and the DNA G+C content was 72.3 mol%. Comparative 16S rRNA gene sequence studies showed that strain A8T belonged to the family Caulobacteraceae, class Alphaproteobacteria and was most closely related to type strains of members of the genus Phenylobacterium (95.7-97.1 % similarity). Signature nucleotides and phylogenetic analysis of the 16S rRNA gene sequence also suggested that strain A8T was affiliated with the genus Phenylobacterium. Low DNA-DNA relatedness values (3.0±1.8-11.5±3.2 %) indicated that strain A8T represented a distinct species that was separated from other type strains in the genus Phenylobacterium. On the basis of evidence from a polyphasic study, it is proposed that strain A8T (=KACC 15042T=LMG 25973T) represents the type strain of a novel species, Phenylobacterium muchangponense sp. nov. An emended description of the genus Phenylobacterium is also presented.