Proposal of Bacillus altaicus sp. nov. Isolated from Soil in the Altai Region, Russia

TL;DR

A new Bacillus species, B. altaicus, is proposed based on a soil isolate from the Altai region with distinct genomic and morphological traits.

Contribution

The paper introduces Bacillus altaicus sp. nov., a novel bacterial species with unique genomic and phenotypic characteristics.

Findings

Strain al37.1T has 61.6% DDH with B. mycoides, meeting species delineation criteria.

The isolate has distinct fatty acid profiles and carbon source utilization compared to B. mycoides.

The strain contains BGCs for antimicrobial and insecticidal compounds and shows cytotoxicity to PANC-1 cells.

Abstract

The Altai Republic remains a geographic region with an uncovered microbial diversity hiding yet undescribed potential species. Here, we describe the strain al37.1T from the Altai soil. It showed genomic similarity with the Bacillus mycoides strain DSM 2048T. However, the in silico DNA–DNA hybridization (DDH) was 61.6%, which satisfies the accepted threshold for delineating species. The isolate formed circular, smooth colonies, in contrast to the rhizoidal morphology typical of B. mycoides. The strain showed optimal growth under the following conditions: pH 6.5, NaCl concentration 0.5% w/v, and +30 °C. The major fraction of fatty acids was composed of C16:0 (34.77%), C18:1 (15.20%), C14:0 (9.06%), and C18:0 (7.88%), which were sufficiently lower in DSM 2048T (C16:0–15.6%, C14:0–3.7%). In contrast to DSM 2048T, al37.1T utilized glycerol, D-mannose, and D-galactose, while being unable to assimilate D-sorbitol, D-melibiose, and D-raffinose. The strain contains biosynthetic gene clusters (BGCs) associated with the production of fengycin, bacillibactin, petrobactin, and paeninodin, as well as loci coding for insecticidal factors, such as Spp1Aa, chitinases, Bmp1, and InhA1/InhA2. The comparative analysis with the 300 closest genomes demonstrated that these BGCs and Spp1Aa could be considered core for the whole group. Most of the strains, coupled with al37.1T, contained full nheABC and hblABC operons orchestrating the synthesis of enteric toxins. We observed a cytotoxic effect (≈19 and 22% reduction in viability) of the strain on the PANC-1 cell line. Given the unique morphological features and genome-derived data, we propose a new species, B. altaicus, represented by the type strain al37.1T.

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