This Article Full Text (PDF) Other Versions of this Article: JB.00979-06v1 188/22/7830    most recent Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Stevenson, L. G. Articles by Rather, P. N. Search for Related Content PubMed PubMed Citation Articles by Stevenson, L. G. Articles by Rather, P. N.

 Previous Article  |  Next Article 

J. Bacteriol. doi:10.1128/JB.00979-06
Copyright (c) 2006, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

A novel gene involved in regulating the flagellar gene cascade in Proteus mirabilis

Department of Microbiology and Immunology , Emory University School of Medicine and Laboratories of Microbial Pathogenesis Veterans Affairs Medical Center, Atlanta, Georgia

^* To whom correspondence should be addressed. Email: prather{at}emory.edu.

	Abstract

In this study, we identified a transposon insertion in a novel gene, designated disA, that restored swarming motility to a putrescine deficient, speA mutant of P. mirabilis. A null allele in disA also increased swarming in a wild-type background. The DisA gene product was homologous to amino acid decarboxylases and its role in regulating swarming was investigated by examining the expression of genes in the flagellar cascade. In a disA mutant background, we observed a 1.4-fold increase in expression of flhDC, which encodes FlhD₂C₂, the master regulator of the flagellar gene cascade. However, the expression of class 2 (fliA, flgM) and class 3 (flaA) genes were at least 16-fold higher in the disA background during swarmer cell differentiation. Overexpression of DisA on a high-copy plasmid did not significantly decrease flhDC mRNA accumulation, but resulted in a complete block in mRNA accumulation for both fliA and flaA. DisA overexpression also blocked swarmer cell differentiation. The disA gene was regulated during the swarming cycle and a single-copy disA::lacZ fusion exhibited a 3-fold increase in expression in swarmer cells. Given that DisA was similar to amino acid decarboxylases, a panel of decarboxylated amino acids were tested for effects similar to DisA overexpression and phenethylamine, the product of phenylalanine decarboxylation, was capable of inhibiting both swarming and expression of class 2 and class 3 genes in the flagellar regulon. A DisA-dependent decarboxylated amino acid may inhibit formation of active FlhD₂C₂ heterotetramers or inhibit FlhD₂C₂ binding to DNA.

This article has been cited by other articles:

• Clemmer, K. M., Rather, P. N. (2008). The Lon protease regulates swarming motility and virulence gene expression in Proteus mirabilis. J Med Microbiol 57: 931-937 [Abstract] [Full Text]  
• Hatt, J. K., Rather, P. N. (2008). Characterization of a Novel Gene, wosA, Regulating FlhDC Expression in Proteus mirabilis. J. Bacteriol. 190: 1946-1955 [Abstract] [Full Text]