Genomic and transcriptomic analysis reveals chitin metabolic pathways in the marine bacterium Microbulbifer harenosus...

Chitin is the second most abundant polysaccharide in nature, and its degradation by marine microorganisms plays a critical role in the global carbon and nitrogen cycles. This study investigated the marine bacterium Microbulbifer harenosus CGMCC 1.13584^T to elucidate its chitin metabolic pathway through genomic and transcriptomic analyses.

When cultured with chitin as the carbon source, the strain exhibited an extended lag phase and enhanced extracellular chitinase activity. Genome sequencing revealed the presence of genes involved in both hydrolytic and oxidative chitin degradation pathways. Transcriptomic analysis showed that genes associated with the hydrolytic pathway were significantly upregulated upon chitin induction. In contrast, within the oxidative degradation pathway, only early-stage response genes (such as those encoding LPMOs) were markedly upregulated, while genes involved in subsequent metabolic steps (converting GlcNAc1A to KDG-6-P) did not show significant upregulation. Furthermore, a gene encoding a GH10 domain-containing protein was found to be substantially upregulated during growth on chitin.

These findings indicate that Microbulbifer harenosus CGMCC 1.13584^T utilizes a coordinated chitin degradation mechanism, where the hydrolytic pathway dominates carbon flux during active growth, while the oxidative pathway (via LPMOs) likely provides critical initial structural disruption.