Streptomyces castrisilvae sp. nov. and Streptomyces glycanivorans sp. nov., novel soil streptomycetes metabolizing mutan and alternan.

Abstract

Six bacterial strains, Mut1^T, Mut2, Alt1, Alt2, Alt3^T, and Alt4, were isolated from soil samples collected in parks in Gothenburg, Sweden, based on their ability to utilize the insoluble polysaccharides α-1,3-glucan (mutan; Mut strains) or the mixed-linkage α-1,3/α-1,6-glucan (alternan; Alt strains). Analysis of 16S rRNA gene sequences identified all strains as members of the genus Streptomyces. The genomes of the strains were sequenced and subsequent phylogenetic analyses identified Mut2 as a strain of Streptomyces laculatispora and Alt1, Alt2 and Alt4 as strains of Streptomyces poriferorum, while Mut1^T and Alt3^T were most closely related to the type strains Streptomyces drozdowiczii NBRC 101007^T and Streptomyces atroolivaceus NRRL ISP-5137^T, respectively. Comprehensive genomic and biochemical characterizations were conducted, highlighting typical features of Streptomyces, such as large genomes (8.0-9.6 Mb) with high G+C content (70.5-72.0%). All six strains also encode a wide repertoire of putative carbohydrate-active enzymes, indicating a capability to utilize various complex polysaccharides as carbon sources such as starch, mutan, and cellulose, which was confirmed experimentally. Based on phylogenetic and phenotypic characterization, our study suggests that strains Mut1^T and Alt3^T represent novel species in the genus Streptomyces for which the names Streptomyces castrisilvae sp. nov. and Streptomyces glycanivorans sp. nov. are proposed, with strains Mut1^T (=DSM 117248^T=CCUG 77596^T) and Alt3^T (=DSM 117252^T=CCUG 77600^T) representing the respective type strains.