Production of xanthan gum by Sphingomonas bacteria carrying genes from Xanthomonas campestris

Abstract

Twelve genes coding for assembly, acetylation, pyruvylation, polymerization, and secretion of the polysaccharide xanthan gum are clustered together on the chromosome of the bacterium Xanthomonas campestris. These genes (gumBCDEFGHIJKLM) are sufficient for synthesis of xanthan gum when placed in bacteria from a different genus, Sphingomonas. The polysaccharide from the recombinant microorganism is largely indistinguishable, structurally and functionally, from native xanthan gum. These results demonstrate that a complex pathway for biosynthesis of a specific polysaccharide can be acquired by a single inter-generic transfer of genes between bacteria. This suggests the biological and commercial feasibility of synthesizing xanthan gum or other polysaccharides in non-native hosts.

Bacterial exopolysaccharides: biosynthesis pathways and engineering strategies

“…Relatively little information is available on EPS with varying monomer composition. The transfer of complete gene clusters toward alternative host strains was reported to result in altered compositions of the repeat units ( Pollock et al, 1997 ; van Kranenburg et al, 1999a ). This effect might result from the different enzymatic equipment of the host strains for nucleotide precursor synthesis ( Stingele et al, 1999 ).…”

Operating bioreactors for microbial exopolysaccharide production

“…However, other factors may also give microbial polysaccharides a distinct edge. It is becoming increasingly easy to metabolically engineer EPS producing strains, or even to move whole genetic elements for EPS synthesis into another host microbe (as with the introduction of the GUM gene cluster into a Sphingomonas from Xanthomonas campestris; Pollock et al, 1997). Health issues and public perceptions may also impact.…”

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

“…Replacement of SpnB (general name for enzymes involved in sphingan biosynthesis, such as gellan, welan and diutan [12] )w ith GumD results in unaltered production of sphingan polysaccharides in various sphingomonades, thus indicating that even with less homology at the nucleotide and structural levels, the same functionc an be obtained in different organisms. [23] Ah igherd egree of identity is described for priming GTsi nG ram-positive bacteria, especially lactobacilli. [24] The first sugar docked by the priming GT at the lipid carrier now serves as acceptor of the next sugar,u ronic acid or as ugar derivative.…”