Sandarakinorhabdus limnophila gen. nov., sp. nov., a novel bacteriochlorophyll a-containing, obligately aerobic bacterium isolated from freshwater lakes

Abstract

Three strains (so36, so42T and wo26) representing a novel Gram-negative, obligately aerobic, bacteriochlorophyll a-containing species of the α-4 subgroup of the Proteobacteria were isolated from freshwater lakes using a high-throughput cultivation technique. The non-motile and slender rod-shaped cells formed orange–red-pigmented colonies. The main carotenoids were nostoxanthin and keto-nostoxanthin. According to the absorption spectrum, two different photosynthetic light-harvesting complexes, an LHI complex and a B800-830-type peripheral LHII complex, were present in the cells. The predominant fatty acids of strain so42T were hexadecenoic acid (16 : 1ω7c) and octadecenoic acid (18 : 1ω7c), whereas 17 : 1ω6c and 14 : 0 iso 2-OH were present in smaller amounts. The main polar lipids were phosphatidylethanolamine, phosphatidylglycerol, phosphatidylcholine, diphosphatidylglycerol, glycolipid and sphingoglycolipids. The major respiratory lipoquinone was ubiquinone-10, whereas ubiquinone-9 was present in smaller amounts. The three strains were cytochrome oxidase-negative and catalase-positive and formed alkaline and acid phosphatases. The strains grew chemoorganoheterotrophically in mineral media supplemented with various organic acids, amino acids or complex substrates such as peptone and yeast extract. The G+C content of the genomic DNA of strain so42T was 64·3 mol%. The three novel isolates contained the same 16S rRNA gene sequence. The 16S rRNA gene sequence similarity to the closest phylogenetic relative Sandaracinobacter sibiricus was only 92·8 %. Accordingly, the three strains represent a new genus and species, for which the name Sandarakinorhabdus limnophila gen. nov., sp. nov., is proposed, with strain so42T (=DSM 17366T=CECT 7086T) as the designated type strain.