Methylibium aquaticum sp. nov., a betaproteobacterium isolated from a eutrophic freshwater pond

Abstract

A freshwater bacterium, designated IMCC1728T, was isolated from a eutrophic pond. The strain was Gram-negative, chemoheterotrophic and facultatively aerobic, forming non-motile rods that contained poly-β-hydroxybutyrate granules. Based on 16S rRNA gene sequence comparisons, the most closely related species to strain IMCC1728T was Methylibium petroleiphilum (97.0 % similarity). Phylogenetic trees generated using 16S rRNA gene sequences showed that this isolate formed an independent phyletic line of the genus Methylibium clade of the class Betaproteobacteria. The DNA G+C content of the strain was 66.2±0.4 mol%. The predominant cellular fatty acid constituents were C16 : 1 ω7c and/or iso-C15 : 0 2-OH (43.1 %), C16 : 0 (20.3 %), C12 : 0 (13.4 %) and C10 : 0 3-OH (7.3 %). The strain contained Q-8 as the predominant ubiquinone. Several phenotypic characteristics, including flagellation, temperature range for growth and carbon source utilization patterns, differentiated strain IMCC1728T from species of the genus Methylibium. Therefore, it is proposed that strain IMCC1728T represents a novel species, Methylibium aquaticum sp. nov. The type strain is IMCC1728T (=KCCM 42364T=NBRC 102349T).