Post-translational modifications in bacteria: From identification to function

Post-translational modifications (PTMs) provide molecular variety beyond the gene or amino acid codes. Diversity stems from a vast number of chemical species or physical changes that are regulated either enzymatically or non-enzymatically to provide transient or prolonged alterations to protein structure and function. Bacteria are wrongly considered "simple" due to their relatively small genomes; however, application of high-resolution methods in enrichment, identification, and quantitation by mass spectrometry (MS) has unleashed a plethora of site-specific PTM data unequivocally demonstrating that bacteria can undertake almost all modifications seen in eukaryotes, while also maintaining novel PTMs that occur specifically in these organisms. Despite this, our ability to exploit omics-level PTM data has not been comparable; determining site stoichiometry, understanding the roles conferred by PTMs, and characterizing the functions of identified PTM sites remain to be routinely achievable at scale. This review examines major PTMs and their importance in generating functional variations in bacterial proteins.