Comparative genomics of Mycoplasma: Insights on genome reduction and identification of potential antibacterial targets

Background: Mycoplasmas are cell wall-deficient bacteria which cause respiratory and urogenital infections in human. Mycoplasmas are resistant to many of the available antibiotics because of their high mutation rates and lack of cell wall. Various studies have identified the emergence of treatment-resistant Mycoplasma isolates. Novel drug target identification has become significant for the development of successful antibacterial treatments. Computational genomic analysis plays a significant role in facilitating the identification of potential drug targets in many bacterial pathogens. Methods: In the present study, 12 Mycoplasma genomes were subjected to comparative genomic analysis to reinforce the understanding of their genomic organization and to identify potential drug targets. The distributions of genes under the Clusters of Orthologous Groups of proteins (COG) functional categories were analyzed for all the 12 Mycoplasma genomes. Genes from each functional category that are conserved across all the Mycoplasma genomes were extracted to identify the backbone genome of Mycoplasma species. The genes in the backbone genome were subjected to similarity search against a database of essential genes to validate their essentiality. Essentiality of these genes was further analyzed based on their function and subcellular localization. Results: The 12 Mycoplasma genomes under study were found to exhibit marked similarities in COG functional category distributions. An overall loss of genes in various functional categories has been observed in all the 12 Mycoplasma genomes. In all the 12 Mycoplasma genomes under study, a maximum reduction in the genes involved in the secondary metabolites biosynthesis, transport, and catabolism (Q) is observed. Conclusion: Comparative genomic studies have identified a set of 170 genes which are commonly present all the 12 Mycoplasma genomes. Further analysis of these genes has identified a set of 158 core essential genes which serve as a promising cluster of novel antibacterial targets.