Sequence and characterization of Bacillus subtilis CheW

A Bacillus subtilis open reading frame (ORF) encoding a predicted polypeptide of 156 amino acids was subcloned and sequenced. The polypeptide was found to be homologous to CheW of Escherichia coli, sharing 28.6% amino acid identity. The ORF was verified by using a bacteriophage T7 expression system in E. coli. The gene was inactivated by insertion of a nonpolor chloramphenicol acetyltransferase cassette in its N-terminal region. In the absence of chemoeffectors, the mutant displayed a smooth swimming bias, with some tumbling. The CheW^- mutant was defective on swarm plates but was complemented by a plasmid that expressed wild type CheW. Addition of attractant or repellent to the CheW^- mutant resulted in transient smooth swimming or tumbling, respectively. However, capillary assays revealed that chemotaxis was substan-tially impaired in the mutant strain.