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. McpA is a chemoreceptor that binds to 12 different L-amino acids and mediates chemotaxis toward these amino acids. Mutant shows different biofilm kinetics, reaching maximal biofilm formation earlier than wild type. Mutation does not affect the capacity to colonize the plant root. Belongs to the methyl-accepting chemotaxis (MCP) protein family.