Description
The degradation of complex marine polysaccharides is a critical component of the global carbon cycle, yet the specific molecular mechanisms employed by many marine Bacteroidetes remain under-characterized. This research focuses on a marine bacteroidete, Cyclobacterium marinum, capable of degrading two algalpolysaccharides found in marine environments: laminarin and fucoidan. Leveraging a multi-omics approach, we utilized transcriptomics and proteomics data to identify Sus-like proteins and Glycoside Hydrolases (GHs) that are significantly upregulated in the presence of laminarin, fucoidan, or both. Interestingly, this strain lacks typical laminarin-degrading enzymes like GH16 or GH30, suggesting the presence of alternative GH families.
Based on these expression profiles, we selected eight SusD-like candidate genes and two GH candidate genes for molecular cloning and functional characterization. SusD-like proteins are essential components of the Starch Utilization System (Sus), acting as cell-surface glycan-binding proteins that facilitate the initial capture and delivery of polysaccharides in the periplasm. The current work involves cloning and screening of 10 candidate genes into the protein expression vector. The successful construction of these recombinant clones and subsequent protein expression are the foundational steps for this study.
The next phases of this research involve the expression and purification of these proteins to conduct detailed protein-polysaccharide interaction studies and enzymatic assays. These experiments are designed to determine the binding affinity and specificity of the SusD-like proteins towards laminarin and fucoidan, alongside the catalytic efficiency of the identified GHs. Understanding the functional roles of these proteins provides crucial insights into the specialized machinery Cyclobacterium uses to harness energy from these polysaccharides, contributing to our broader understanding of marine carbon cycling and microbial ecology.