An exopolysaccharide pathway from a freshwater Sphingomonas isolate

Area of Science:

• Microbiology
• Biochemistry
• Synthetic Biology

Background:

• Bacteria synthesize diverse polysaccharides for cell envelope functions, with complex biosynthetic pathways leading to varied structures and properties.
• Characterizing these pathways is crucial for understanding glycan diversity and unlocking biotechnological potential.
• Many bacterial polysaccharide biosynthetic pathways remain uncharacterized due to their complexity.

Purpose of the Study:

• To isolate and characterize a novel exopolysaccharide (EPS) from Sphingomonas sp. LM7.
• To identify and elucidate the genes responsible for the biosynthesis of this EPS.
• To compare the identified pathway with known polysaccharide biosynthesis pathways in other bacteria.

Main Methods:

• Isolation of Sphingomonas sp. LM7 from Lake Michigan.
• Screening of a transposon mutant library to identify genes involved in EPS production.
• Gene cluster identification and deletion to confirm roles in EPS biosynthesis.
• Extraction and chemical analysis of the produced EPS to determine its composition and linkage types.

Main Results:

• Identification of a novel EPS, promonan, produced by Sphingomonas sp. LM7.
• Characterization of a complete wzy/wzx-dependent gene cluster essential for promonan production.
• Determination that promonan consists of a linear chain of 3- and 4-linked glucose, galactose, and glucuronic acid residues.
• Demonstration that the promonan pathway is distinct from other known bacterial polysaccharide pathways.

Conclusions:

• The identified gene cluster is essential for promonan biosynthesis in Sphingomonas sp. LM7.
• Promonan represents a novel class of bacterial polysaccharides with a unique structure and biosynthetic pathway.
• The characterized pathway provides a foundation for potential engineering of novel polysaccharides with desirable properties.