The distributed genome hypothesis as a rubric for understanding evolutionin situduring chronic bacterial biofilm infectious processes

Abstract

Most chronic infectious disease processes associated with bacteria are characterized by the formation of a biofilm which provides for bacterial attachment to the host tissue or implanted medical device. The biofilm protects the bacteria from the host’s adaptive immune response, as well as predation by phagocytic cells. However, the most insidious aspect of biofilm biology from the host’s point of view is that the biofilm provides an ideal setting for bacterial horizontal gene transfer (HGT). HGT provides for large-scale genome content changes in situ during the chronic infectious process. Obviously, for HGT processes to result in the reassortment of alleles and genes among bacterial strains the infection must be polyclonal (polymicrobial) in nature. In this review we marshal the evidence that all of the factors are present in biofilm infections to support HGT which results in the ongoing production of novel strains with unique combinations of genic characters and that the continual production of large numbers of novel, but related bacterial strains leads to persistence. This concept of an infecting population of bacteria undergoing mutagenesis to produce a ‘cloud’ of similar strains to confuse and overwhelm the host’s immune system parallels genetic diversity stratagies employed by viral and parasitic pathogens.

Wounds, Functional Disability, and Indwelling Devices Are Associated With Cocolonization by Methicillin-Resistant Staphylococcus aureus and Vancomycin-Resistant Enterococci in Southeast Michigan

“…Consistent with our findings is that 10 of 11 previously reported cases of VRSA were identified from wounds [18]. Wounds may be an important reservoir for VRSA emergence because of the propensity for biofilm formation within wounds; biofilms can enhance bacterial growth and lateral gene transfer [19].…”

IS5 inserts upstream of the master motility operon flhDC in a quasi-Lamarckian way

“…For insertion of IS5 into both the bgl and glpFK operons, the environment influences the mutation rate. In addition, in biofilms, some cells increase their mutation rate during stress by increasing competence during chronic infections (Ehrlich et al, 2010). Hence, these examples demonstrate a Lamarckian-type evolution (that is, environment-driven mutation) that differs from that of Darwin, which holds that mutation rates should not depend on the environment (Koonin and Wolf, 2009).…”

Diagnostic Microbiology: Present Status and Future Prospect

“…However, wholegenome sequencing (WGS) has shown that multiple strains with the same PFGE and MLST patterns have significantly different genetic contents and these methods lack the resolution to provide strain specific diagnostics at this point 6 . Ultrasequencing or pyrosequencing has demonstrated multiple strains of HIV-1 within a single individual and identification of minority mutants in the quasi-species.…”