Evolution of pathogenic bacteria from non-pathogenic species by horizontal gene transfer and mutation.

By Maxwell Addo 

The pathogenic bacterium, Y. pestis, can evolve from a non-pathogenic environmental strain, by incorporating genetic information obtained from the environment into its genome by horizontal gene transfer (HGT) and mutation. Y. pestis caused the bubonic plague.                                             

The non-pathogenic environmental strain acquired a plasmid pCD1, forming a virulent strain, which later acquired other elements to diverge into Y. enterocolitica and Y. pseudotuberculosis. Y. pestis evolved from Y. pseudotuberculosis  by acquiring genes and losing some genes, which makes it possible for Y. pestis to be transmitted by bites of fleas.                                                                            

This shows that the emergence of disease-causing bacteria and its eradication is a repeated and continuous process in our present world. Bacillus antracis and Francisella tularensis are other examples of this case. Generally, the process is aided by non-pathogenic bacteria gaining access into pathogenicity islands and interacting with the elements (for example, plasmids) there. Analyzing pathogenic bacteria genomes shows the incorporation of novel genes into the genome of a non-virulent strain

 

 Figure from mini-review by Martínez  JL. (2013) showing evolutional steps of Y. pestis from an environmental non-pathogenic strain published in Environmental Microbiology Journal, February 2013 edition.

Original Article: Martínez  JL. (2013). Bacterial pathogens: from natural ecosystems to human hosts. Environ Microbiol 15: 325–333.