Pseudomonas composti sp. nov., isolated from compost samples

Abstract

Two unusual, Gram-negative, catalase- and oxidase-positive rods, designated C2T and C5, were isolated from compost samples. Comparative 16S rRNA gene sequencing studies demonstrated that both isolates were members of the genus Pseudomonas and belonged to the Pseudomonas aeruginosa group. Strain C2T was most closely related to Pseudomonas cuatrocienegasensis 1NT and Pseudomonas borbori R-20821T (97.9 and 97.8 % 16S rRNA gene sequence similarity, respectively). However, phylogenetic analysis based on rpoD gene sequences revealed that both isolates could be discriminated from members of the P. aeruginosa group that exhibited >97 % 16S rRNA gene sequence similarity. The DNA G+C content of strain C2T was 61.5 mol%. The major fatty acids of strain C2T were a summed feature (C16 : 1ω7c and/or iso-C15 : 0 2-OH), C18 : 1ω7c/12t/9t, C16 : 0 and C12 : 0, which supported the isolates’ affiliation with the genus Pseudomonas. Moreover, strain C2T could be distinguished from its closest phylogenetic neighbours of the genus Pseudomonas by DNA–DNA hybridization studies and biochemical tests. On the basis of both phenotypic and phylogenetic findings, it is proposed that the isolates be classified as a novel species, with the name Pseudomonas composti sp. nov. The type strain is C2T ( = CECT 7516T = CCUG 59231T).