Williamsia herbipolensis sp. nov., isolated from the phyllosphere of Arabidopsis thaliana

A Gram-stain-positive, non-endospore-forming actinobacterium (ARP1T) was isolated from the phyllosphere of Arabidopsis thaliana. On the basis of 16S rRNA gene sequence phylogeny strain ARP1T was placed into the genus Williamsia and the closest related species were Williamsia phyllosphaerae (98.5 % 16S rRNA gene sequence similarity), Williamsia deligens (98.5 %), Williamsia maris (98.3 %) and Williamsia serinedens (98.2 %). Genome-based comparison indicated a clear distinction to the type strains of those species with pairwise average nucleotide identities (ANI) between 76.4-78.4 %. The quinone system of strain ARP1T consisted predominantly of menaquinones MK-9(H2), MK-7(H2) and MK-8(H2), and the polar lipid profile contained the major compound diphosphatidylglycerol, and moderate amounts of phosphatidylethanolamine, phosphatidylglycerol and numerous unidentified lipids. Mycolic acids were present. These chemotaxonomic traits and the major fatty acids, which were C16 : 1ω7c, C16 : 0, C18 : 0, C18 : 1ω9c and tuberculostearic acid supported the affiliation of strain ARP1T to the genus Williamsia. Genotypic, physiological and biochemical testing revealed clear differences of strain ARP1T to the most closely related species of the genus Williamsia. Therefore strain ARP1T represents a novel species of this genus, for which the name Williamsia herbipolensis sp. nov. is proposed. The type strain is ARP1T (=DSM 46872T=LMG 28679T).