High receptor methylation would also enhance cluster stability, leading to stronger amplification of signals under conditions of Selleckchem FRAX597 the reduced ligand binding noise at high concentrations of ambient attractant. Figure 4 Two regimes

of bacterial chemotaxis behaviour and their characteristic features. Attractant gradient is indicated. At low concentrations or absence of attractant the behaviour is explorative, while at high concentrations of attractant the behaviour is tracking. See text for details. Finally, we demonstrated the thermal stability of the chemosensory complexes in vivo, which may be an important component of the overall thermal robustness of the chemotaxis pathway [44]. This is consistent with the ability of the common wild type E. coli strains to chemotax efficiently up to 42°C. In these strains, the reduction of the chemotaxis and flagellar

gene expression at high temperature is further balanced by high basal levels of the respective proteins, thus ensuring that chemotaxis is supported throughout the entire physiological range of temperatures. Methods Bacterial strains and plasmids Anlotinib mw All strains used for FRAP measurements are derivatives of the E. coli K-12 strain RP437 that is conventionally used as the wild type for chemotaxis studies [56]: VS102 carries a deletion of the anti-sigma-factor flgM, resulting in an approximately 6-fold over-expression of all chemotaxis proteins [45], which has been previously shown to facilitate FRAP measurements of chemotaxis clusters in E. coli [37]. LL4 (ΔflgM ΔcheY-cheZ) and LL5 (ΔflgM ΔcheR-cheZ) served as backgrounds corresponding to receptors in low- and intermediate Ureohydrolase modification

state, respectively. In addition, common E. coli K-12 wild type strains MG1655 and W3110 were used as controls for studies of temperature effects on chemotaxis. YFP tagged chemotaxis proteins were expressed from the vector plasmid pTrc99a (Ampr) under control of an isopropyl-β-D-thiogalactopyranoside (IPTG) inducible pTrc promoter [57]. Site-specific mutagenesis was used to introduce mutations into catalytic sites of CheR and CheB [36, 40, 46]. As reported previously, YFP fusions to CheR and CheB are fully functional, whereas fusions to CheA and CheW do not efficiently support chemotaxis but show proper localization to receptor clusters and interactions with their respective binding partners [36, 40, 46]. All expression constructs for the YFP fusions and respective induction levels employed for FRAP are presented in Table 1.