Behavioral Adaptation in Bacillus Subtilis: The Role of Selective Methylation Changes and Heterologous Receptors in Mcpb-Mediated Signaling

109 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2001.The methylation-independent system is proposed to involve the regulation of higher-order receptor complexes. Therefore, asparagine chemotaxis likely depends on the presence of heterologous receptors. To explore these processes, a study was performed on strains expressing mutant McpB proteins (with aspartates substituted at the sites of methylation) in genetic backgrounds missing all ten receptors, five receptors, or only the native copy of mcpB. These aspartate substitutions ensure a negative charge at the altered sites. This analysis revealed the following: (1) only migration toward high concentrations of asparagine was impaired; (2) the presence of all heterologous receptors fully compensated for this defect; (3) methyl-group turnover occurred on heterologous receptors in response to the McpB-mediated attractant asparagine, and these methylation changes were required for the restoration of normal taxis; (4) migration towards asparagine in these mutants progressively worsened as more receptors were taken away; (5) in the absence of the methylesterase, the presence of heterologous receptors in some cases impaired taxis; and (6) either a certain threshold number of receptors must be present to promote basal CheA activity, or one or more of the receptors missing in the 10del background but present in 5del background is required for establishing basal CheA activity. Taken together, these findings suggest the chemoreceptors work as an ensemble that constitutes a robust chemotaxis system.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD