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Background:  We use bacteria as model organisms for addressing one of the most fundamental problems in cell biology -- How do cells divide? More specifically, we want to know how the division septum is formed and how its formation is regulated. Another objective is to understand how proteins are targeted to specific subcellular sites, especially how cell division proteins localize to the midcell.

Recent Results:  We have approached these issues by screening for and/or characterizing new cell division proteins of Escherichia coli. In the last year or so, my lab has published on an ABC transporter named FtsEX, a periplasmic protein named FtsP (formerly called SufI), and, most recently, three new division proteins named DamX, DedD and RlpA.  The three new proteins (DamX, DedD, RlpA) all contain a C-terminal “SPOR” domain that binds to the peptidoglycan cell wall.  Surprisingly, we found that the SPOR domain alone is able to localize to the midcell.  We think SPOR domains must be binding to a special peptidoglycan form (or structure) in the division septum.  Figuring out what that structure is might provide important new insights concerning peptidoglycan synthesis during cell division.

Future Directions:  The questions we are addressing now include: What sequences in SPOR domains specify septal localization? What is the unique feature of septal peptidoglycan that SPOR domains recognize?  What role do the SPOR domain proteins play in cell division?  In this regard, it is important to note that DamX, DedD and RlpA all have multiple domains, so we think that investigations of the SPOR domains will tell only part of the story behind what these proteins are doing.  Beyond the SPOR domain proteins, we have ongoing projects to investigate other new (as yet unpublished) proteins involved in cell division in E. coli and a project concerning regulation of cell division in a pathogenic bacterial species named Vibrio parahaemolyticus.  The Vibrio project is in collaboration with Linda McCarter, another faculty member in our department.

Significance:  A better understanding of cell division and protein localization in E. coli might shed light on these processes in other organisms. In addition, our studies might lead to more knowledge-based approaches to developing new antibiotics.