Roseisolibacter agri gen. nov., sp. nov., a novel slow-growing member of the under-represented phylum Gemmatimonadetes

A novel slow-growing bacterium, designated strain AW1220 T , was isolated from agricultural floodplain soil sampled at Mashare (Kavango region, Namibia) by using a high-throughput cultivation approach. Strain AW1220 T was characterized as a Gram-negative, non-motile, rod-shaped bacterium. Occasionally, some cells attained an unusual length of up to 35 µm. The strain showed positive responses for catalase and cytochrome-c oxidase and divided by binary fission and/or budding. The strain had an aerobic chemoorganoheterotrophic metabolism and was also able to grow under micro-oxic conditions. Colonies were small and pink pigmented. Strain AW1220 T was found to be a mesophilic, neutrophilic and non-halophilic bacterium. Cells accumulated polyphosphate intracellularly and mainly utilized complex protein substrates for growth. 16S rRNA gene sequence comparisons revealed that strain AW1220 T belonged to the class Gemmatimonadetes (=group 1). Its closest relatives were found to be Gemmatimonas aurantiaca T-27 T (90.9 % gene sequence similarity), Gemmatimonas phototrophica AP64 T (90.8 %) and Longimicrobiumterrae CB-286315 T (84.2 %). The genomic G+C content was 73.3 mol%. The major fatty acids were iso-C15 : 0, C16 : 1ω7c and/or iso-C15 : 0 2-OH, iso-C17 : 1ω9c, iso-C15 : 0 3-OH and C16 : 0. The predominant respiratory quinone was MK-9, albeit minor amounts of MK-8 and MK-10 are also present. The polar lipids comprised major amounts of phosphatidylethanolamine, phosphatidylcholine, diphosphatidylglycerol and one unidentified phosphoglycolipid. On the basis of its polyphasic characterization, strain AW1220 T represents a novel genus and species of the class Gemmatimonadetes for which the name Roseisolibacter agri gen. nov., sp. nov. is proposed, with the type strain AW1220 T (=DSM 104292 T =LMG 29977 T ).