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J. Bacteriol. doi:10.1128/JB.01253-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Regulation of Aggregatibacter (Actinobacillus) actinomycetemcomitans leukotoxin secretion by iron

Department of Oral Biology, New Jersey Dental School, University of Medicine and Dentistry of New Jersey, Newark, NJ 07103; Public Health Research Institute, International Center for Public Health, 225 Warren St., Newark, New Jersey 07103

^* To whom correspondence should be addressed. Email: kachlasc{at}umdnj.edu.

	Abstract

The Gram negative oral and systemic pathogen, Aggregatibacter (Actinobacillus) actinomycetemcomitans, produces leukotoxin (LtxA) that is a member of the Repeats in Toxin (RTX) family of secreted bacterial toxins. We have recently shown that LtxA has the ability to lyse erythrocytes that results in a beta-hemolytic phenotype on Columbia blood agar. To determine if LtxA is regulated by iron, we examined beta-hemolysis under iron-rich and iron-limiting conditions. Beta-hemolysis was suppressed in the presence of FeCl₃. In contrast, strong beta-hemolysis occurred in the presence of the iron chelator, deferoxamine (DFO). We found that secretion of LtxA was completely inhibited by free iron, but expression of ltxA was not regulated by iron. Free chromium, cobalt, and magnesium did not affect LtxA secretion. Other LtxA associated genes were not regulated by iron. Thus, iron appears to play an important role in the regulation of LtxA secretion in A. actinomycetemcomitans in a manner independent of gene regulation.

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