Unraveling the Genomic Potential of the Thermophilic Bacterium Anoxybacillus flavithermus from an Antarctic Geothermal Environment

Abstract

Antarctica is a mosaic of extremes. It harbors active polar volcanoes, such as Deception Island, a marine stratovolcano having notable temperature gradients over very short distances, with the temperature reaching up to 100 °C near the fumaroles and subzero temperatures being noted in the glaciers. From the sediments of Deception Island, we isolated representatives of the genus Anoxybacillus, a widely spread genus that is mainly encountered in thermophilic environments. However, the phylogeny of this genus and its adaptive mechanisms in the geothermal sites of cold environments remain unknown. To the best of our knowledge, this is the first study to unravel the genomic features and provide insights into the phylogenomics and metabolic potential of members of the genus Anoxybacillus inhabiting the Antarctic thermophilic ecosystem. Here, we report the genome sequencing data of seven A. flavithermus strains isolated from two geothermal sites on Deception Island, Antarctic Peninsula. Their genomes were approximately 3.0 Mb in size, had a G + C ratio of 42%, and were predicted to encode 3500 proteins on average. We observed that the strains were phylogenomically closest to each other (Average Nucleotide Identity (ANI) > 98%) and to A. flavithermus (ANI 95%). In silico genomic analysis revealed 15 resistance and metabolic islands, as well as genes related to genome stabilization, DNA repair systems against UV radiation threats, temperature adaptation, heat- and cold-shock proteins (Csps), and resistance to alkaline conditions. Remarkably, glycosyl hydrolase enzyme-encoding genes, secondary metabolites, and prophage sequences were predicted, revealing metabolic and cellular capabilities for potential biotechnological applications.

Keywords: Anoxybacillus; antarctica; comparative genomics; phylogeny; polar volcano; potential metabolic functions.

Figure 1

Genomic and metagenomic data on Anoxybacillus available in public databases. (a) Geographical distribution of Anoxybacillus strains. (b) Described species belonging to Anoxybacillus (n = 18) and the number of sequenced genomes in each species (draft and complete genomes, n = 34). Data were generated by PATRIC.

Figure 2

(a) Global similarity phylogenomic tree (based on ANIb and TETRA results) consisting of Brevibacillus (B_), Geobacillus (G_), Anoxybacillus (A_), and our genomes (LAT_11, LAT_26, LAT_27, LAT_31, LAT_33, LAT_35, and LAT_38). The colors distinguish the two main clades. (b) Phylogenomic tree (maximum likelihood estimation); the tree is colored by genus: yellow represents the genus Geobacillus, blue represents Brevibacillus, and green represents Anoxybacillus. Clusters with dotted lines correspond to the Antarctic Anoxybacillus strains isolated in the present study.

Figure 3

Circular visualization of the genome comparisons of Anoxybacillus strains and Geobacillus stearothermophilus DSM 458 (reference), created by BRIG. The inner black circle contains the complete reference genome (strain DSM 458), and the intensity of each color indicates the similarity of that strain with the reference genome.

Figure 4

Functional analysis of Anoxybacillus strains described in the present study. (a) Number of genes related to metabolic functions in Anoxybacillus strains. (b) PCA plot of the annotated functional categories in Anoxybacillus strains; the Anoxybacillus strains are represented by dots, and the functional categories are represented by numbered green vectors. The angles and lengths of radiating vectors indicate the direction and strength of the relationships between the function and strain, respectively.