Systems analysis of the glycoside hydrolase family 18 enzymes from characterizes essential chitin degradation functions.

Understanding the strategies used by bacteria to degrade polysaccharides constitutes an invaluable tool for biotechnological applications. Bacteria are major mediators of polysaccharide degradation in nature; however, the complex mechanisms used to detect, degrade, and consume these substrates are not well-understood, especially for recalcitrant polysaccharides such as chitin. It has been previously shown that the model bacterial saprophyte is able to catabolize chitin, but little is known about the enzymatic machinery underlying this capability. Previous analyses of the genome and proteome indicated the presence of four glycoside hydrolase family 18 (GH18) enzymes, and studies of the proteome indicated that all are involved in chitin utilization. Using a combination of and approaches, we have studied the roles of these four chitinases in chitin bioconversion. Genetic analyses showed that only the gene product is essential for the degradation of chitin substrates. Biochemical characterization of the four enzymes showed functional differences and synergistic effects during chitin degradation, indicating non-redundant roles in the cell. Transcriptomic studies revealed complex regulation of the chitin degradation machinery of and confirmed the importance of Chi18D and LPMO10A, a previously characterized chitin-active enzyme. With this systems biology approach, we deciphered the physiological relevance of the glycoside hydrolase family 18 enzymes for chitin degradation in , and the combination of and approaches provided a comprehensive understanding of the initial stages of chitin degradation by this bacterium.