Isolation and Genomic Characterization of Myxococcus faecalis Strains from Mangroves in Southeastern Brazil

Abstract Myxococcus faecalis was recently described from human fecal isolates, although subsequent evidence indicates an environmental distribution for this lineage. Here, we report the isolation and genomic characterization of two M. faecalis strains (BRX-014 and BRX-032) recovered from mangrove ecosystems along the southeastern coast of Brazil, representing the first record of the species in a marine-coastal biome. Phylogenomic reconstruction based on 120 conserved bacterial marker genes, together with Average Nucleotide Identity (ANI >97.6%) and digital DNA–DNA hybridization (dDDH 77.7–90.4%) analyses, confirmed their assignment to M. faecalis and demonstrated high genomic relatedness to strains previously recovered from soil and human feces samples. Pangenome analysis of five available genomes revealed a total repertoire of 9,827 genes, with a large core genome comprising 7,499 genes (76.3%), consistent with a highly conserved and nearly closed pangenome structure. Functional classification based on COG categories showed uniform distributions across all isolates. Comparative analysis of the degradome further revealed strong conservation of proteolytic and carbohydrate-active enzyme repertoires, dominated by serine and metallopeptidases and diverse glycoside hydrolases. The extensive genomic and functional similarity among isolates from geographically distant and ecologically distinct environments supports a broad ecological distribution of M. faecalis and suggests that its large and conserved genomic repertoire underpins its persistence across contrasting habitats. These findings expand the known ecological range of the species and provide a comparative genomic framework for future investigations into its distribution and functional potential across different habitats. Competing Interest Statement The authors have declared no competing interest.