Dictyobacter aurantiacus gen. nov., sp. nov., a member of the family Ktedonobacteraceae, isolated from soil, and emended description of the genus Thermosporothrix

Abstract

A mesophilic, Gram-stain-positive, spore-forming bacterium that formed branched mycelia was isolated from paddy soil in Gunung Salak (Mount Salak), West Java, Indonesia. This strain, designated S-27T, grew at temperatures between 20 and 37 °C; the optimum growth temperature was 25 to 30 °C, and no growth was observed at 15 or 45 °C. The pH range for growth was pH 3.5 to 8.6; the optimum pH was 6.0, and no growth was observed at pH 3.0 or 9.2. Strain S-27T was able to hydrolyse polysaccharides such as starch, cellulose and xylan. The G+C content of the DNA of strain S-27T was 55.7 mol%. The major fatty acids were iso-C17 : 0 and C16 : 1 2-OH, and the major menaquinone was MK-9 (H2). The cell wall of strain S-27T contained d-glutamic acid, glycine, l-alanine, d-alanine, l-ornithine and β-alanine in a molar ratio of 1.0 : 1.6 : 1.4 : 0.6 : 0.9 : 1.1. The polar lipids consisted of phosphatidylglycerol, phosphatidylinositol and two glycolipids. The major cell-wall sugar was arabinose. Detailed phylogenetic analysis based on 16S rRNA gene sequences indicated that strain S-27T belongs to the order Ktedonobacterales and is most closely related to Ktedonobacter racemifer SOSP1-21T (89.6 % sequence identity). On the basis of its chemotaxonomic and phenotypic features and phylogenetic position, we concluded that strain S-27T represents a novel genus and species, for which we propose the name Dictyobacter aurantiacus gen. nov., sp. nov. The type strain of Dictyobacter aurantiacus is strain S-27T (=NBRC 109595T=InaCC B312T). Emendation of the description of the genus Thermosporothrix is also provided.

Dictyobacter vulcani sp. nov., belonging to the class Ktedonobacteria, isolated from soil of the Mt Zao volcano

“…The class Ktedonobacteria was initially established in 2006 for the Gram-positive, aerobic, mycelia-and spore-forming branching lineage in the phylum Chloroflexi [1] and, at the time or writing, contains six genera and 13 formally proposed mesophilic and thermophilic species [1][2][3][4][5][6][7][8][9]. Strains belonging to this class were characterized with actinomycete-like morphologies [1][2][3][4][5][6][7][8][9], relatively large genomes (5.54-13.66 Mb) [10][11][12], ubiquity in various terrestrial environments [13][14][15][16][17][18] and having potential for secondary metabolism [12,[19][20][21].…”

“…The genus Dictyobacter was proposed by Yabe et al in 2017 for a mesophilic clade in the class Ktedonobacteria that now contains three formally proposed species [3,6]. Dictyobacter aurantiacus grows optimally at 25-30 °C and pH 6.0 [6], while D. alpinus and D. kobayashii grow optimally at 20-30 °C and pH 6.0-7.0 [3].…”

“…The genus Dictyobacter was proposed by Yabe et al in 2017 for a mesophilic clade in the class Ktedonobacteria that now contains three formally proposed species [3,6]. Dictyobacter aurantiacus grows optimally at 25-30 °C and pH 6.0 [6], while D. alpinus and D. kobayashii grow optimally at 20-30 °C and pH 6.0-7.0 [3]. Unlike other spore-forming Ktedonobacteria species, D. aurantiacus forms sporangia on branched vegetative mycelia in prolonged culture [22]; D. alpinus and D. kobayashii also form spore-or sporangium-like structures [3].…”

Prokaryotic community shifts during soil formation on sands in the tundra zone

“…Family Ktedonobacteraceae belonging to phylum Chloroflexi that were predominate in unfixed sands are known to be negatively correlated with organic matter content in deforested soil [50]. This family is mostly represented by uncultivable genera; its cultivable representatives are filamentous, aerobic and mesophilic [51]. Ktedonobacteraceae was previously found in young soils [20,52,53]; thus, we suggest that representatives of this family are important at initial successional stages.…”

Cellulolytic enzyme-producing thermophilic Actinobacteria isolated from the soil of Cisolok Geysers, West Java, Indonesia

“…Seven isolates (SL1-1-R-2, SL1-1-R-4, SL1-1-R-7, SL1-1-R-8, SL1-2-R-2, SL1-2-R-3, and SL1-2-R-4) were obtained from soil around a big geyser (6 o 57'221"S, 106 o 27'507"E), three isolates (SL2-2-R-1, SL2-2-R-12, and SL2-2-R-15) were obtained from soil around a small geyser (6 o 57'189"S, 106 o 27'365"E), and seven isolates (SL3-1-R-14, SL3-1-R-16, SL3-2-R-5, SL3-2-R-17, SL3-2-R-18, SL3-2-R-33, and SL3-2-R-37) were obtained from forest soil near a geyser (6 o 57'482"S, 106 o 28'655"E). Thermophilic Actinobacteria were isolated according to Yabe et al (2017) and with some modifications. The isolation was performed using 1% International Streptomyces Project (ISP) 1 agar medium incubated at 45°C for 3 to 4 weeks.…”