Chemotactic-signal transducers respond to changes in the concentration of attractants and repellents in the environment, transduce a signal from the outside to the inside of the cell, and facilitate sensory adaptation through the variation of the level of methylation. PscA recognizes specifically and with high affinity L-Asp, D-Asp and L-Glu. It exerts a double function, in mediating chemotaxis to these amino acids and in modulating cyclic di-GMP (c-di-GMP) levels, causing alterations in biofilm development. Plays a key role in the infection process. It may facilitate bacterial entry into the plant. Mutant does not respond to L-Asp, whereas chemotaxis to D-Asp and L-Glu is significantly reduced. Mutant shows increased c-di-GMP level, a modest but significant increase in biofilm formation and reduced swarming motility. It also shows reduced virulence in tomato plants. Belongs to the methyl-accepting chemotaxis (MCP) protein family.