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 RXD178(T), RXD172-2 and RLT1W51(T), 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 RXD178(T), RXD172-2 and RLT1W51(T) 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 RLT1W51(T) were 98.27 and 83.50 %, respectively. The three novel strains contained C-16:0, C-17:0 cyclo and summed feature 3 (C-16:1 omega 6c and/or C-16:1 omega 7c) as the major fatty acids, and summed feature 8 (C-18:1 omega 6c and/or C-18:1 omega 7c) comprised a relative higher proportion in strain RXD178(T) than in other strains. Both strains RXD172-2 and RLT1W51(T) 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 RXD178(T). Ubiquinone 8 was the predominant quinone. Based on the phenotypic, chemotaxonomic, phylogenetic and genomic analyses, strain RXD178(T) should be considered as representing one novel species within the genus Collimonas and strains RXD172-2 and RLT1W51(T) as another one, for which the names Collimonas silvisoli sp. nov. and Collimonas humicola sp. nov. are proposed, with RXD178(T) (=GDMCC 1.1925(T)=KACC 21987(T)) and RLT1W51(T) (=GDMCC 1.1923(T)=KACC 21985(T)) as the type strains, respectively.

Automated summary

Three novel aerobic, Gram-negative, non-motile, rod-shaped bacteria isolated from Nanling National Nature Reserve in Guangdong Province belonged to the genus Collimonas. Detailed analyses led to the proposal of two new species within this genus, with distinct genetic and phenotypic characteristics.