E-Letter responses to:

review: Christophe Fraser, William P. Hanage, and Brian G. Spratt Recombination and the Nature of Bacterial Speciation Science 2007; 315: 476-480 [Abstract] [Full text] [PDF]

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Published E-Letter responses:

Reponse to A. Jeltsch’s E-Letter

Christophe Fraser, William P. Hanage and Brian G. Spratt   (10 July 2007)

Role of Restriction/Modification System in Bacterial Speciation

Albert Jeltsch   (6 April 2007)

Reponse to A. Jeltsch’s E-Letter 10 July 2007
Christophe Fraser, Reader in Theoretical Biology Department of Infectious Disease Epidemiology, Imperial College London, UK., William P. Hanage and Brian G. Spratt Respond to this E-Letter: Re: Reponse to A. Jeltsch’s E-Letter	We agree that it has been known for some time that restriction/modification (RM) systems can form a barrier to recombination, and that other authors (1) including Jeltsch (2) have suggested they could be important in causing reproductive isolation. However, we are unaware of any data that actively implicate them in the process of speciation, as opposed to hypothesizing that they could be involved. RM systems are generally considered to have evolved to protect against phage (3), although other roles have been suggested (4, 5). In many species, recombination occurs by transformation (including many with very high rates of recombination), and the effect of RM systems on the uptake and integration of linear fragments is not usually considered to be very greatly affected by differences in restriction systems (3); furthermore, the production of linear fragments by restriction may even promote recombination (5). Therefore, we think it is unlikely that RM systems have anything like a universal role in reducing recombination between subpopulations within an existing species, and hence speciation. Christophe Fraser, William P. Hanage, Brian G. Spratt Department of Infectious Disease Epidemiology, Imperial College London, UK. References 1. C. Berndt, P. Meier, W. Wackernagel, Microbiology 149, 895 (2003). 2. A. Jeltsch, Gene 317, 13 (2003). 3. T. A. Bickle, D. H. Kruger, Microbiol. Rev. 57, 434 (1993). 4. I. Kobayashi, Nucleic Acids Res. 29, 3742 (2001). 5. N. E. Murray, Microbiology 148, 3 (2002).
Role of Restriction/Modification System in Bacterial Speciation 6 April 2007
Albert Jeltsch, Prof. of Biochemistry International University Bremen Respond to this E-Letter: Re: Role of Restriction/Modification System in Bacterial Speciation	Fraser et al. state that restriction/modification systems (RM-systems) have not yet been implicated in the process of bacterial speciation. This model has already been described in detail in 2003 (1). It proposes that constituting a barrier to horizontal gene transfer is one central biological function of restriction/modification systems. Different RM-systems present in a single bacterial species divide it into different biotypes, which do not exchange genes among each other. Such division of one species into different biotypes expressing different and mutually exclusive RM-systems is an ideal starting point for a rapid adaptation to different ecological niches. Furthermore, a role of RM-systems in speciation explains the wide distribution of such systems in nature and the presence of several systems in individual cells. Reference A. Jeltsch, Gene 317, 13 (2003).