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Appl. Environ. Microbiol. doi:10.1128/AEM.01232-07
Copyright (c) 2007, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

Characterization of regulatory pathways in Xylella fastidiosa: genes and phenotypes controlled by algU

Department of Plant Pathology, University of California, Riverside, California 92521; Institute of Agricultural and Environmental Research, Tennessee State University, Nashville, Tennessee 37209

^* To whom correspondence should be addressed. Email: donald.cooksey{at}ucr.edu.

	Abstract

Many virulence genes in plant bacterial pathogens are coordinately regulated by "global" regulatory genes. Conducting DNA microarray analysis of bacterial mutants of such genes, compared with wild-type, can help to refine the list of genes that may contribute to virulence in bacterial pathogens. The regulatory gene, algU, with roles in stress response and regulation of the biosynthesis of the exopolysaccharide (EPS) alginate in Pseudomonas aeruginosa and many other bacteria has been extensively studied. The role of algU in Xylella fastidiosa, the cause of Pierce's disease of grapevines, was analyzed by mutation and whole-genome microarray analysis to define its involvement in aggregation, biofilm formation, and virulence. In this study, an algU::nptII mutant had reduced cell-cell aggregation, attachment, biofilm formation, and lower virulence in grapevines. Microarray analysis showed that 42 genes had significantly lower expression in the algU::nptII mutant than the wild type. Among these are several genes that could contribute to cell aggregation and biofilm formation, as well as other physiological processes such as virulence, competition, and survival.