1.Metabolic flux pattern of glucose utilization by Xanthomonas campestris pv. campestris: prevalent role of the Entner-Doudoroff pathway and minor fluxes through the pentose phosphate pathway and glycolysis.
Schatschneider S1, Huber C, Neuweger H, Watt TF, Pühler A, Eisenreich W, Wittmann C, Niehaus K, Vorhölter FJ. Mol Biosyst. 2014 Oct;10(10):2663-76. doi: 10.1039/c4mb00198b.
The well-studied plant pathogenic bacterium Xanthomonas campestris pv. campestris (Xcc) synthesizes the biotechnologically important polysaccharide xanthan gum, which is also regarded as a virulence factor in plant interactions. In Xcc, sugars like glucose are utilized as a source to generate energy and biomass for growth and pathogenicity. In this study, we used [1-(13)C]glucose as a tracer to analyze the fluxes in the central metabolism of the bacterium growing in a minimal medium. (13)C-Metabolic flux analysis based on gas chromatography-mass spectrometry (GC-MS) confirmed the prevalent catabolic role of the Entner-Doudoroff pathway. Comparative nuclear magnetic resonance (NMR)-based isotopologue profiling of a mutant deficient in glycolysis gave evidence for a moderate flux via glycolysis in the wild-type. In addition to reconfirming the Entner-Doudoroff pathway as a catabolic main route, this approach affirmed a numerically minor but important flux via the pentose phosphate pathway.
2.Biophysical characterization of the outer membrane polysaccharide export protein and the polysaccharide co-polymerase protein from Xanthomonas campestris.
Bianco MI1, Jacobs M1, Salinas SR1, Salvay AG2, Ielmini MV1, Ielpi L3. Protein Expr Purif. 2014 Sep;101:42-53. doi: 10.1016/j.pep.2014.06.002. Epub 2014 Jun 10.
This study investigated the structural and biophysical characteristics of GumB and GumC, two Xanthomonas campestris membrane proteins that are involved in xanthan biosynthesis. Xanthan is an exopolysaccharide that is thought to be a virulence factor that contributes to bacterial in planta growth. It also is one of the most important industrial biopolymers. The first steps of xanthan biosynthesis are well understood, but the polymerization and export mechanisms remain unclear. For this reason, the key proteins must be characterized to better understand these processes. Here we characterized, by biochemical and biophysical techniques, GumB, the outer membrane polysaccharide export protein, and GumC, the polysaccharide co-polymerase protein of the xanthan biosynthesis system. Our results suggested that recombinant GumB is a tetrameric protein in solution. On the other hand, we observed that both native and recombinant GumC present oligomeric conformation consistent with dimers and higher-order oligomers.
3.Structure of xanthan gum and cell ultrastructure at different times of alkali stress.
de Mello Luvielmo M1, Borges CD2, de Oliveira Toyama D3, Vendruscolo CT4, Scamparini AR3. Braz J Microbiol. 2016 Jan-Mar;47(1):102-9. doi: 10.1016/j.bjm.2015.11.006. Epub 2016 Jan 27.
The effect of alkali stress on the yield, viscosity, gum structure, and cell ultrastructure of xanthan gum was evaluated at the end of fermentation process of xanthan production by Xanthomonas campestris pv. manihotis 280-95. Although greater xanthan production was observed after a 24h-alkali stress process, a lower viscosity was observed when compared to the alkali stress-free gum, regardless of the alkali stress time. However, this outcome is not conclusive as further studies on gum purification are required to remove excess sodium, verify the efficiency loss and the consequent increase in the polymer viscosity. Alkali stress altered the structure of xanthan gum from a polygon-like shape to a star-like form. At the end of the fermentation, early structural changes in the bacterium were observed. After alkali stress, marked structural differences were observed in the cells. A more vacuolated cytoplasm and discontinuities in the membrane cells evidenced the cell lysis.
4.Draft genome of the xanthan producer Xanthomonas campestris NRRL B-1459 (ATCC 13951).
Wibberg D1, Alkhateeb RS2, Winkler A1, Albersmeier A1, Schatschneider S2, Albaum S1, Niehaus K2, Hublik G3, Pühler A1, Vorhölter FJ4. J Biotechnol. 2015 Jun 20;204:45-6. doi: 10.1016/j.jbiotec.2015.03.026. Epub 2015 Apr 9.
Xanthomonas campestris NRRL B-1459 was used in pioneering studies related to the biotechnological production of xanthan, the commercially most important polysaccharide of bacterial origin. The analysis of its genome revealed a 5.1Mb chromosome plus the first complete plasmid of an X. campestris strain applied in biotechnology.