Cloning of the genes of the chitin utilization regulon of Serratia liquefaciens.

The set of genes that determine the expression of the enzymes involved in chitin degradation by Serratia liquefaciens was cloned. The role of each gene was investigated, and for the first time regulatory genes were identified in this system. The chiA and chiB genes coded for separate chitinase activities. The chiC region coded for a chitobiase activity, but it was not formally separated from chiB. Transposon mutagenesis and deletion analysis identified a region, chiD, whose absence led to higher expression of chiA, chiB, and chiC. chiD may therefore be a gene that codes for a repressor. Loss of function of another adjacent region, chiE, prevented induction unless a chiE+ strain was a near neighbor, suggesting that this gene may code for a protein that is involved in the synthesis of the inducer. chiB, chiC, chiD, and chiE are closely linked, while chiA is in a separate location on the chromosome.