YmoA Negatively Regulates Expression of Invasin fromYersiniaenterocolitica

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Abstract
invencodes invasin, which is the primary invasion factor ofYersinia enterocolitica. invexpression in vitro is regulated in response to temperature, pH, and growth phase. In vitro,invis maximally expressed at 26°C and repressed at 37°C at neutral pH but, when the pH of the media is adjusted to 5.5, levels ofinvexpression at 37°C are comparable to those at 26°C. A previous genetic screen for regulators ofinvidentified RovA, which was found to be required for activation ofinvin vitro under all conditions tested as well as in vivo. Here we describe a screen that has identified a negative regulator ofinvexpression,ymoA. TheymoBAlocus was identified by transposon mutagenesis as a repressor ofinvexpression in vitro at 37°C at neutral pH. This mutant shows increasedinvexpression at 37°C. The mutant can be fully complemented forinvexpression by a plasmid expressingymoA. These results indicate that YmoA plays a role in the negative regulation ofinv.