Identification and organization of genes for diutan polysaccharide synthesis from Sphingomonas sp. ATCC 53159

Abstract

A cluster of genes for diutan polysaccharide synthesis was isolated from a library of Sphingomonas sp. ATCC 53159 genomic DNA by complementation of glucosyl-isoprenylphosphate transferase-deficient mutants of Sphingomonas elodea ATCC 31461 (producing gellan) and Xanthomonas campestris (producing xanthan). The synthesis of polysaccharide in these strains shares a common first step, transfer of glucose-1-phosphate from UDP-glucose to the isoprenylphosphate lipid. The cluster of 24 genes was compared to genes for biosynthesis of gellan, and S-88 sphingan from Sphingomonas sp. ATCC 31554. Diutan, gellan and S-88 sphingan have a common four-sugar backbone but different side chains, one rhamnose for S-88 sphingan, a two-rhamnose side chain for diutan and no side chain for gellan. The genes for biosynthesis of diutan, gellan and S-88 sphingan were similar in general organization but differed in location of some genes, in particular, dpsG (putative polymerase), dpsR (putative lyase) and dpsS (putative repeat unit transporter). An unidentified reading frame urf31, present in the gene clusters for diutan and S-88 sphingan but not gellan, had similarity to glycosyl transferase group 2 proteins, and was detrimental when cloned in Sphingomonas elodea producing gellan that lacks a side chain, but not in Sphingomonas ATCC 31554 producing S-88 sphingan with a rhamnose side chain. Gene urf31 could possibly encode a side-chain rhamnosyl transferase. Another gene urf31.4 was unique to the diutan gene cluster. A plasmid containing 20 of the 24 genes resulted in a slight increase in the amount of diutan produced, but a significant increase in the rheological properties of diutan.

Production and Rheological Properties of Welan Gum Produced by <b><i>Sphingomonas</i></b> sp. ATCC 31555 with Different Nitrogen Sources

“…Sphingans are a group of exopolysaccharides (EPS) secreted by Sphingomonas , such as gellan, welan, diutan, and rhamsan [Coleman et al, 2008;Hagiwara et al, 2010;Schmid et al, 2014Schmid et al, , 2015Wang et al, 2012]. Sphingans have a common tetrasaccharide backbone structure which contains glucose, glucuronic acid, rhamnose, and mannose [Seo et al, 2004].…”

Bacterial Polysaccharides: Production and Applications in Cosmetic Industry

“…5) (Coleman et al 2008). Both substituents are located on the same glucose residue, and on average, there is one glycerate per repeat and one acetate per every two repeats.…”

Enzymatic Transformations Involved in the Biosynthesis of Microbial Exo‐polysaccharides Based on the Assembly of Repeat Units

“…[25] Here, the exact functionh as not yet been assigned; however,i ti sk nownt hat the genes named "unknown reading frames" urf31.4, urf31 and urf34 are involved. [26] Whether the addition of mannose or rhamnose as side chain occurs as the final step of repeatu nit assembly or at the nascentr epeat unit remains speculative.…”