Dictyobacter halimunensis sp. nov., a new member of the phylum Chloroflexota, from forest soil in a geothermal area

Abstract

Three Gram-stain-positive aerobic bacteria, characterized by branched mycelia with putative sporangia, were isolated from forest soil inside a decayed bamboo stem from a geothermal area in West Java, Indonesia. The strain S3.2.2.5T grew at 15–37 °C (optimum 30 °C), at pH 5.0–7.0 (optimum 7.0) and in the presence of 0–1% NaCl (optimum 0%). Strain S3.2.2.5T was able to hydrolyse cellulose, xylan, starch and skim milk. The cell-wall sugars were composed of xylose and mannose, and the peptidoglycan hydrolysates contained d-glutamic acid, glycine, d-alanine, l-alanine, β-alanine and l-ornithine. The major fatty acids (>10%) were anteiso-C17:0, iso-C17:0, C16:1 2-OH and iso-C16:1. The major polar lipids were phosphatidylinositol, phosphatidylglycerol, diphosphatidylglycerol, unidentified glycolipids and unidentified phospholipids. The major menaquinone was MK-9 (H2). The results of the analysis of the phylogenetic tree based on the 16S rRNA gene indicated that these three isolates belong to the genus Dictyobacter and they were most closely related to the type strain of species Dictyobacter aurantiacus S-27T (97.41–98.00%). The strain S3.2.2.5T exhibited a genome size of 9.41 Mbp, which was significantly larger than the known Dictyobacter species. The G+C content was 54.3 mol%. The average nucleotide identity (90.77%) and the digital DNA–DNA hybridization values (42.6%) between strain S3.2.2.5T and D. aurantiacus S-27T were below the threshold value for species delineation. Based on the phenotypic, chemotaxonomic and molecular characteristics of strain S3.2.2.5T, a novel species of the genus Dictyobacter, for which the name Dictyobacter halimunensis sp. nov., is proposed. The type strain is S3.2.2.5T (= UICC B-128T = CGMCC 1.61913T = KCTC 43728T).