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

A strictly aerobic, bacteriochlorophyll a -containing betaproteobacterium , designated strain W35 ^T , 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 W35 ^T was closely related to species in the genus Aquabacterium . The closest phylogenetic relatives of strain W35 ^T were Aquabacterium commune B8 ^T (97.9 % sequence similarity), Aquabacterium citratiphilum B4 ^T (97.2 %) and Aquabacterium limnoticum ABP-4 ^T (97.0 %). The major cellular fatty acids were C _{16  :  1} ω7 c (50.4 %), C _{16  :  0} (22.7 %), summed feature 8 (C _{18  :  1} ω7 c /C _{18  :  1} ω6 c ; 9.7 %), C _{18  :  3} ω6 c (5.5 %), C _{12  :  0} (5.3 %) and C _{10  :  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 W35 ^T is 6.1 Mbp and average nucleotide identity analysis indicated genome similarities of strain W35 ^T and related Aquabacterium type strains to be 78-79 %. The results of polyphasic comparisons showed that strain W35 ^T 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 W35 ^T (=DSM 106757 ^T =NBRC 111963 ^T ). The description of the genus Aquabacterium is also emended.