Putative evolution of <i>Myxococcus fulvus</i> 124B02 plasmid pMF1 from a chromosomal segment in another <i>Myxococcus</i> species

Myxobacteria or order Myxococcales (old nomenclature) or phylum Myxococcota (new terminology) are fascinating organisms well known for their diverse peculiar physiological, taxonomic, and genomic properties. Researchers have long sought to identify plasmids within these organisms, yet thus far, only two organisms from different families have been found to harbor a plasmid. This study delves into the putative evolution of one of these plasmids, i.e., pMF1 present in <i>Myxococcus fulvus</i> 124B02 in the suborder Cystobacterineae and family Myxococcaceae. Here, we first reannotated the pMF1 plasmid genome sequence and identified two additional open reading frames or putative genes which were not annotated until now. We further reported that all pMF1 plasmid genes depict homology with <i>Myxococcus stipitatus</i> CYD1 draft genome (contig 28) and a chromosomal segment of <i>M. stipitatus</i> DSM14675 in a syntenic manner, implying the presence of plasmid-like structure in <i>M. stipitatus</i> CYD1, integrated into its chromosome. To comprehend the relationship among these three species, we conducted phylogenetic analyses using 16S and concatenated housekeeping genes and genome-to-genome distance calculator (GGDC) analysis, which confirmed that <i>M. stipitatus</i> CYD1 is a distinct and novel species within the genus <i>Myxococcus</i>. Overall, this comparative genomic study sheds light on the putative emergence of the pMF1 plasmid from a common ancestor of closely related yet distinct species, <i>M. stipitatus</i> CYD1, possibly through the partition from its chromosome as a segment.IMPORTANCEMyxobacteria are not well known to have plasmids. Until now, only two organisms have been shown to have plasmids, raising a pertinent question about how these plasmids evolved randomly within the phylum Myxococcota. The study presented in this manuscript delves into the emergence of the pMF1 plasmid found in <i>Myxococcus fulvus</i> 124B02, a member of the suborder Cystobacterineae and family Myxococcaceae. Our research addresses this intriguing topic of plasmid identification and evolution within myxobacteria, which are a group of fascinating organisms that have garnered significant interest due to their diverse physiological, taxonomic, and genomic properties.