Site specific recombination and replicon stability

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In this study, we wish to examine how a bacteria's genetic material separates before the cell divides.  This process is very complex and requires that the cell properly synchronizes the events of DNA replication and cell division.  One of the problems that can arise during this process is when the cell's DNA molecules recombine with each other prior to cell division.  This results in an enlarged DNA molecule that cannot be effectively separated, resulting in an unequal distribution of genetic material.  To counteract this problem, bacteria have devised a way to restore  these enlarged DNA molecules into their original state using a genetic process called site-specific recombination.  This process occurs just before cell division, ensuring that both daughter cells receive the correct amount of genetic material.  In most bacteria, this process uses two proteins called the XerC and XerD recombinases.  These proteins act at specific sites on chromosomes and plasmids, which are mini-chromosomes responsible for transmission of resistance among bacteria.  In addition to XerC and XerD, other cellular proteins are required to ensure that the recombination reaction can occur.  It is the study of these recombination systems, and their accessory factors that interests our laboratory.  We use the ColE1 plasmid as a model to study this system.  ColE1 uses ArgR and PepA as accessory factors for the XerC and XerD proteins.  We believe that ArgR and PepA act together to form a presynaptic complex, which allows XerC and XerD to bind to ColE1 and perform the recombination reaction.  In addition to the separation of chromosomes, the Xer recombination may have other effects.  We have recently found that a functional recombination system is important for growth and chain length in streptococcal bacteria, and may also contribute to the pathogenicity of these bacteria.  The main thrust of our research is to understand how the Xer recombination complex forms, how the genes encoding these proteins are regulated, and what other cellular processes may use these proteins.