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Cyclic di-GMP regulates biofilm formation in Erwinia amylovora through cellulose biosynthesis
L. F. CASTIBLANCO (1), G. W. Sundin (2). (1) Michigan State Univ, East Lansing, MI, U.S.A.; (2) Michigan State University, East Lansing, MI, U.S.A.

Cyclic di-GMP (c di-GMP) is a ubiquitous bacterial secondary messenger molecule that regulates a broad range of cellular processes including exopolysaccharide biosynthesis, biofilm formation, motility, virulence, adhesion, cell cycle and differentiation, among others. After the perception of environmental signals, the intracellular concentration of c di-GMP is modified by enzymatic synthesis or degradation. Subsequent downstream signal transduction and phenotypic modulation is achieved by binding of c di-GMP to specific receptor molecules. Although activation of biofilm formation by high intracellular c di-GMP levels has been previously reported in <i>Erwinia amylovora</i>, the molecular mechanism involved in the modulation of this cellular process have not been characterized. Using gene overexpression and site-directed mutagenesis analyses, we investigated the role of c di-GMP on cellulose biosynthesis and identified one candidate receptor protein, EAM_3387 (BcsA), that encodes the cellulose synthase catalytic subunit and contains the c di-GMP binding domain PilZ. We determined that posttranslational activation of cellulose biosynthesis by binding of c di-GMP to BcsA mediates the c di-GMP-dependent activation of biofilm formation in <i>E. amylovora</i>. Our results present evidence of the molecular signaling mechanism employed by <i>E. amylovora</i> to regulate late stage infection phenotypes such as biofilm formation through c di-GMP

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