Evolution of CS1 pili

[ecoli]

I need some help here (cough... CharonY... cough).

 

For my Darwinian medicine class we have to write about a paper about the evolution of an infectious disease. Wanting to kill two birds and get stoned, I decided I should write about my ongoing research project.

Now, my research is purely about CS1 pili subunit interaction... not about how they evolved in ETEC. But, I read some stuff in papers about how the CS1 pilus system and its related genes probably evolved as a result of horizontal transfer, which resulted in a pathogenecity island. This transfer was most likely selected for by pressures from the immune system.

 

The problem with this, is that I need more references. I need journals that directly study the evolution of this system, if any exist. I've read homology studies, that show interspecies sequencing, but is there more about how/when the horizontal transfer could have occured and more about the selection pressures that could have favored its evolution?

 

THANKS!

[CharonY]

Ugh, studying evolution on this level in bacteria can often be a no-joy as HGE can be quite nasty to track.

The majority of evolutionary papers in this field thus concentrate on the structure and selection constraints of given domains (e.g. Ravi P. Anantha et al. Infection and Immunity, December 2004, p. 7190-7201, Vol. 72, No. 12).

 

Regarding the mechanisms of transmission, more is known. The operon of encoding the pilus are flanked by IS elements, indicating that this is a kind of genomic island (or islet), as you have already mentioned, moreover it is located on a plasmid, again a mobile genetic vehicle. A nice paper about the requirements on the mobility of this plasmid (pCoo) is this one: Barbara Froehlich et al., Journal of Bacteriology, May 2004, p. 3230-3237, Vol. 186, No. 10. and Journal of Bacteriology, September 2005, p. 6509-6516, Vol. 187, No. 18.

 

While not precisely dealing with CS1 pili this review gives a nice overview about pathogenicity islands in general, something which in principal is also applicapble to the evolution of ETEC strans: Herbert Schmidt and Michael Hensel, Clinical Microbiology Reviews, January 2004, p. 14-56, Vol. 17, No. 1.

 

I think to recall that I should also have some paper about the evolution of pathogenic E. coli strains somewhere, though I am pretty sure that again, the focus is on pathogenicity islands rather than on specific pili. But I'd have to dig a bit for them. I'll get back to you soonish.

[ecoli]

Thanks... these will be helpful.

[CharonY]

Sorry, I almost forgot about this thread.

I have here a couple of reviews regarding HGE and pathogenicity islands. To my knowledge most papers dealing with the evolution of CS1 pili focus on its distribution via HGE and its relatedness with other fimbriae (from your OP I gather that you got these papers already).

So to speculate about the evolution of it will require the discussion of the spread of pathogenicity islands and other mobile genetic elements. Here are some reviews dealing with this matter, mostly from a genomic perspective. It is important not to get too much entangled into the details but to find the common theme:

 

Lawrence:Horizontal and Vertical Gene Transfer: The Life History of Pathogens

in: Russell W, Herwald H (eds): Concepts in Bacterial Virulence. Contrib Microbiol. Basel, Karger, 2005, vol 12, pp 255-271 (DOI: 10.1159/000081699)

 

Binnewies et al. : Funct Integr Genomics. 2006 Jul;6(3):165-85.

 

Manson and Gilmore: Mol Microbiol. 2006 Aug;61(3):555-9.

 

Gal-Mor and Finlay: Cell Microbiol. 2006 Nov;8(11):1707-19.