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Coflocculation of Escherichia coli and Schizosaccharomyces pombe
1Department of Food and Microbial Technology, Katholieke Universiteit Leuven, Heverlee, Belgium.
Abstract:
Several yeasts, such as Candida utilis, Dekkera bruxellensis, Hanseniaspora guilliermondii, Kloeckera apiculata, Saccharomyces cerevisiae and Schizosaccharomyces pombe, were found to coaggregate with Escherichia coli, but S. pombe showed much less coflocculation than the other yeasts (Peng et al. 2001)). S. pombe is known to have galactose-rich cell walls and we investigated whether this might be responsible for its different behavior by studying the wild-type TP4-1D, with a mannose to galactose ratio of 1 to 1.2, and the glycosylation mutant gms1delta (Man:Gal=1:0). The wild-type induced very low levels of coflocculation (3%) while gms1delta induced a remarkable amount of coflocculation (48%). Coflocculation of the mutant was inhibited by mannose but not affected by galactose or glucose. The S. cerevisiae mnn2 mutant, with a mannan structure similar to gms1delta, also showed a high degree of coflocculation (40%). However, S. cerevisiae mutant mnn9, with a mature core similar to S. pombe, showed decreased coflocculation (21.3%). Both these S. cerevisae mutants were sensitive to mannose inhibition. Coflocculation of E. coli and gms1delta also could be inhibited by gms1delta mannan and plant lectins, such as HHA, GNA and NPA, specific to either alpha-1-3- or alpha-1-6-linked mannosyl units. From these results we conclude that the E. coli lectins may have specificity for alpha-1-6- and alpha-1-3-linked mannose residues either in the outer chain or in the core of S. pombe, but in wild-type strains these mannose residues are shielded by galactose residues.
Insights
Schizosaccharomyces pombe yeast coflocculation with Escherichia coli is mediated by mannose residues. Altering the mannose-galactose ratio in yeast cell walls significantly impacts this interaction, revealing E. coli lectin specificity.
Area of Science:
- Microbiology
- Yeast-bacteria interactions
- Cell wall glycosylation
Background:
- Several yeast species coaggregate with Escherichia coli.
- Schizosaccharomyces pombe exhibits significantly lower coflocculation with E. coli compared to other yeasts.
- S. pombe possesses galactose-rich cell walls, suggesting a role in its distinct interaction behavior.
Purpose of the Study:
- To investigate the role of cell wall mannose and galactose composition in yeast-bacteria coflocculation.
- To determine the specific mannose linkages recognized by E. coli lectins on S. pombe.
- To elucidate the mechanism behind the reduced coflocculation of wild-type S. pombe.
Main Methods:
- Comparative analysis of coflocculation between wild-type S. pombe (TP4-1D) and a glycosylation mutant (gms1delta) with altered mannose-to-galactose ratios.
- Utilized Saccharomyces cerevisiae mutants (mnn2, mnn9) with known cell wall mannan structures for comparison.
- Investigated inhibition of coflocculation using mannose, galactose, glucose, specific mannans, and plant lectins (HHA, GNA, NPA).
Main Results:
- The gms1delta mutant, with a high mannose content (Man:Gal=1:0), showed significantly increased coflocculation (48%) compared to wild-type S. pombe (3%).
- Coflocculation of the gms1delta mutant was inhibited by mannose and specific mannans, as well as lectins targeting alpha-1-3- and alpha-1-6-linked mannose.
- S. cerevisiae mnn2 mutant also exhibited high coflocculation, while mnn9 showed reduced coflocculation, correlating with mannan structure and S. pombe wild-type.
Conclusions:
- Escherichia coli lectins exhibit specificity for alpha-1-6- and alpha-1-3-linked mannose residues in yeast cell walls.
- In wild-type S. pombe, galactose residues shield these mannose residues, reducing E. coli coflocculation.
- Glycosylation patterns, specifically the mannose-galactose ratio and mannose linkage types, are critical determinants of yeast-E. coli coflocculation.