Aquabacterium pictum sp. nov., the first aerobic bacteriochlorophyll a-containing fresh water bacterium in the genus Aquabacterium of the class Betaproteobacteria

Abstract

A strictly aerobic, bacteriochlorophyll a-containing betaproteobacterium, designated strain W35T, was isolated from a biofilm sampled at Tama River in Japan. The non-motile and rod-shaped cells formed pink-beige pigmented colonies on agar plates containing organic compounds, and showed an in vivo absorption maximum at 871 nm in the near-infrared region, typical for the presence of bacteriochlorophyll a. The new bacterial strain is Gram-negative, and oxidase- and catalase-positive. Phylogenetic analysis based on 16S rRNA gene sequence showed that strain W35T was closely related to species in the genus Aquabacterium . The closest phylogenetic relatives of strain W35T were Aquabacterium commune B8T (97.9 % sequence similarity), Aquabacterium citratiphilum B4T (97.2 %) and Aquabacterium limnoticum ABP-4T (97.0 %). The major cellular fatty acids were C16 : 1ω7c (50.4 %), C16 : 0 (22.7 %), summed feature 8 (C18 : 1ω7c/C18 : 1ω6c; 9.7 %), C18 : 3ω6c (5.5 %), C12 : 0 (5.3 %) and C10 : 0 3OH (2.7 %). The respiratory quinone was ubiquinone-8. Predominant polar lipids were phosphatidylethanolamine, phosphatidylglycerol and diphosphatidylglycerol. The G+C content of the genomic DNA was 70.4 mol% (genome data) and 71.4 mol% (HPLC). The genome size of strain W35T is 6.1 Mbp and average nucleotide identity analysis indicated genome similarities of strain W35T and related Aquabacterium type strains to be 78–79 %. The results of polyphasic comparisons showed that strain W35T was clearly distinguishable from other members of the genus Aquabacterium . Therefore, we propose a new species in the genus Aquabacterium , namely, Aquabacterium pictum sp. nov. The type strain is W35T (=DSM 106757T=NBRC 111963T). The description of the genus Aquabacterium is also emended.