The distributed genome hypothesis as a rubric for understanding evolution in situ during chronic bacterial biofilm infectious processes.
Most chronic infectious disease processes associated with bacteria are characterized by the formation of a biofilm that provides for bacterial attachment to the host tissue or the 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 that results in the ongoing production of novel strains with unique combinations of genic characteristics 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 strategies used by viral and parasitic pathogens.
Ehrlich
Garth D
GD
Center for Genomic Sciences, Allegheny Singer Research Institute, Pittsburgh, PA, USA. garthdehrlich@gmail.com
Ahmed
Azad
A
Earl
Josh
J
Hiller
N Luisa
NL
Costerton
J William
JW
Stoodley
Paul
P
Post
J Christopher
JC
DeMeo
Patrick
P
Hu
Fen Ze
FZ
D001419:Bacteria / Q000235:genetics*; D001422:Bacterial Adhesion; D001424:Bacterial Infections / Q000382:microbiology; D018407:Bacterial Physiological Phenomena; D018441:Biofilms / Q000254:growth & development*; D019143:Evolution, Molecular; D022761:Gene Transfer, Horizontal; D016680:Genome, Bacterial; D006801:Humans