UC San Diego

Escherichia coli is a genetically diverse species, representing pathogenic, probiotic, and commensal strains, while E. coli K-12 is a commonly laboratory strain. Pathogenic strains of E. coli are known to cause urinary tract infections, diarrhea, hemorrhagic colitis, and pyelonephritis worldwide. In addition, there are two probiotic strains, E. coli Nissle 1917 and O83, which have been shown to combat

inflammatory bowel disease. In this study, we identify the transport systems and their substrates within five E. coli strains, two pathogens, two probiotics, and K-12, to identify

transport systems characteristic of either probiotic or pathogenic species. We found that the probiotic and pathogenic strains generally contain more iron-siderophore and sugar transporters than E. coli K-12. Pathogens have an increased number of pore-forming toxins and protein secretion systems than the probiotic strains do. Both pathogens and probiotic strains encode sugar transporters that reflect their intracellular or extracellular environments. In general, both groups seem to show high similarity, suggesting that only a few virulence factors can convert a beneficial microorganism into a pathogenic one. Taken together, these results provide a starting point for future engineering or other applied studies on probiotic bacteria.