Collimonas silvisoli sp. nov. and Collimonas humicola sp. nov., two novel species isolated from forest soil.

Three aerobic, Gram-stain-negative, non-motile and rod-shaped bacteria, designated strains RXD178T, RXD172-2 and RLT1W51T, were isolated from two forest soil samples of Nanling National Nature Reserve in Guangdong Province, PR China. Phylogenetic analyses based on 16S rRNA gene sequences and 92 core genes showed that they belonged to the genus Collimonas, and were most closely related to four validly published species with similarities ranging from 99.4 to 98.2 %. The genomic DNA G+C contents of strains RXD178T, RXD172-2 and RLT1W51T were 57.1, 59.5 and 59.4 mol%, respectively. The genome-derived average nucleotide identity (ANI) and digital DNA-DNA hybridization (dDDH) values between the novel strains and closely related type species were below 37.90 and 89.34 %, respectively. Meanwhile, the ANI and dDDH values between strains RXD172-2 and RLT1W51T were 98.27 and 83.50 %, respectively. The three novel strains contained C16 : 0, C17 : 0 cyclo and summed feature 3 (C16 : 1 ω6c and/or C16 : 1 ω7c) as the major fatty acids, and summed feature 8 (C18 : 1 ω6c and/or C18 : 1 ω7c) comprised a relative higher proportion in strain RXD178T than in other strains. Both strains RXD172-2 and RLT1W51T had phosphatidylglycerol (PG), phosphatidylethanolamine (PE), diphosphatidylglycerol (DPG) and an unidentified aminophospholipid (APL) as the main polar lipids while only PE and APL were detected in strain RXD178T. Ubiquinone 8 was the predominant quinone. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic analyses, strain RXD178T should be considered as representing one novel species within the genus Collimonas and strains RXD172-2 and RLT1W51T as another one, for which the names Collimonas silvisoli sp. nov. and Collimonas humicola sp. nov. are proposed, with RXD178T (=GDMCC 1.1925T=KACC 21987T) and RLT1W51T (=GDMCC 1.1923T=KACC 21985T) as the type strains, respectively.