||P.1300 right column bottom paragraph to p.1301 left column top paragraph: "It is also interesting to compare the cellular abundances of CheA and CheY to those of the histidine kinases (HKs) and response regulators (RRs) in other two-component signaling systems. Table S9 provides such a comparison for E. coli. The protein abundance data come from several published studies and show significant variability, which may be explained by differences in media, growth phases, strains, and techniques, and the comparison should thus be taken with caution. However, it appears that CheA proteins are orders of magnitude more highly expressed than all the other HKs for which data are available (Table S9). The comparison is less striking for CheY, since it does not appear to be particularly highly expressed among RRs in the data from Taniguchi et al. (ref 59 BNID 106257), but the protein abundance measured in Li and Hazelbauer (ref 16 BNID 107850) is much higher and would place CheY among the most highly expressed RRs (Table S9). Although in E. coli, CheA and CheY are expressed at comparable levels (ref 16), a number of other RRs are one or two orders of magnitude more highly expressed than their cognate HKs (Table S9)."