Characterisation of Exiguobacterium abrahamii sp. nov., a novel strain isolated from mangrove soil with lanthipeptide biosynthetic genes

Abstract

Exiguobacterium species are known for their adaptability to extreme environments, making them valuable candidates for biotechnological applications. This study aimed to characterise a novel Exiguobacterium isolate, designated TBG-PICH-001^T, isolated from the Pichavaram estuaries in Tamil Nadu, India, and to determine its taxonomic position within the genus. A polyphasic approach combining phenotypic, genotypic and chemotaxonomic was employed to characterise the isolate TBG-PICH-001. Morphological and biochemical characterisation revealed that the strain is a Gram-positive, motile, rod-shaped, non-spore-forming bacterium that exhibited a characteristic yellow pigmentation. Whole genome sequencing and annotation determined the G + C content to be 47%. Phylogenetic analysis based on 16S rRNA gene positioned that strain TBG-PICH-001^T is closely related to E. acetylicum strain DSM 20416 (NR_043479.1:1–1550), E. indicum strain HHS31 (NR_042347.1:1–1502), and E. enclense strain NIO-1109 (NR_178487.1:1–1415), while the digital DNA-DNA hybridisation (dDDH) confirmed that the organism belongs to the Exiguobacterium genus. Fatty acid analysis showed that the major fatty acid was C16.0 (30.95%), followed by iso-C15.0 (12.87%), iso-C13.0 (11.91%), C18.0 (11.06%), anteiso-C13.0 (10.39%), iso-C17.0 (8.55%), anteiso-C15.0 (3.22%), and C14.0 (2.49%). The strain shows resistance to cold temperatures and high salt concentrations. Genomic analysis revealed the presence of stress response genes and transporters, suggesting that the strain is well adapted to survive in harsh environments. AntiSMASH analysis of the genome showed the presence of lantipeptide biosynthetic genes, suggesting the strain's potential to produce antimicrobial compounds. Biochemical, genotypic, and chemotaxonomic characterisation strongly supports the strain TBG-PICH-001^T as a novel species within the Exiguobacterium genus and named Exiguobacterium abrahamii sp. nov. This study enhances the understanding of Exiguobacterium diversity and its adaptability to diverse environments, opening a new avenue for biotechnology exploration.