Pathogenicity islands: bacterial evolution in quantum leaps.

摘要: Is the acquisition of a pathogenicity island sufficient to transform an organism into pathogen? Three factors determine virulence role islands: genes within island, status recipient microorganism, and features host that promote progression disease. The incorporation certain genes, such as those encoding cholera toxin, would be convert any pathogen because administration toxin itself is produce symptoms But for most other cases, utility sequences obtained through gene transfer varies with organism. E. coli benign constituent mammalian intestinal flora apparently predisposed become by introduction several types genes. LEE likely encode all necessary attachment effacement lesions, this could probably render strain pathogenic. And, not surprisingly, islands causing these lesions have been detected in genetically diversed strains coli.The offers rapid method evolving novel functions; however, introgressed sequences, even when they their specific regulators part complete functional units, must interact rest genome. Expression six invasion SPI-1 Salmonella governed PhoP/PhoQ regulatory system (Galan 1996xGalan, J.E. Mol. Microbiol. 1996; 20: 263–272Crossref | PubMed Scopus (329)See ReferencesGalan 1996), which encoded present both pathogenic non-pathogenic microorganisms. And are maintained on extrachromosomal elements can regulated chromosomal loci: Shigella plasmid controlled chromosomally-encoded histone-like protein H1.The association mobile DNA suggests incorporated wide variety bacterial species. However, presence does assure transformation pathogen. A 10 kb region harbors known species Listeria (L. monocytogenes L. ivanovii) also chromosome nonpathogenic seeligeri (Gouin et al. 1994xGouin, E, Mengaud, J, Cossart, P. Infect. Immun. 1994; 62: 3550–3553PubMedSee ReferencesGouin 1994). While cluster encodes pleiotropic activator, attenuated phenotype has ascribed down regulation Furthermore, due coevolution between microbes hosts, potential will only manifest suitable animals plants.Finally, it suggested deletion may represent mechanism control expression (Blum 1994xBlum, G, Ott, M, Lischewski, A, Ritter, Imrich, H, Tschape, Hacker, J. 606–614PubMedSee ReferencesBlum This presupposes elimination circumvent immune response determinants allow microbial replication reducing size. plausible scenario, contain surface antigens response, growth rates natural under lab conditions associated genome Therefore, employed bacteria modulate virulence, but simply reflects intrinsic genetic instability sequences.