A Bacillus amyloliquefaciens ChbB protein binds beta- and alpha-chitin andhas homologues in related strains

A small (19.8 kDa) protein was identified in Bacillus amyloliquefaciens ALK O 2718 cultures during growth in the presence of yeast extract and chitin, but not with glucose. The protein targets beta -chitin best, then alpha -ch itin, but barely any other polysaccharide. This described chitin-binding pr otein (ChbB) is the first of other polysaccharide. This described chitin-bi nding protein (ChbB) Is the first its type from a Bacillus strain and cross -reacts with antibodies raised against the Streptomyces alpha -chitin-bindi ng protein CHB1. Using reverse genetics, the chromosomal chbB gene of strai n ALKO 2718 was identified, cloned and sequenced. ChbB shares several motif s with the alpha -chitin-binding proteins CHB1 and CHB2 of Streptomyces and CBP21 of Serratia marcescens predominantly targeting beta -chitin. Synthes is was repressed by glucose and the presence of cre boxes suggests cataboli te control. Using PCR, Southern hybridization and anti-ChbB antibodies, the presence of a chbB gene, as well as of a ChbB protein homologue, was ascer tained in several tested B. amyloliquefaciens strains, but not in Bacillus subtilis 168. Contrary to B. subtilis 168, all B. amyloliquefaciens strains secreted varying amounts of enzymic activity, degrading carboxymethyl chit in coupled with Remazol brilliant violet.