The influence of a modified lipopolysaccharide O-antigen on the biosynthesis of xanthan in Xanthomonas campestris pv. campestris B100

Steffens T, Vorhölter F-J, Giampa M, Hublik G, Pühler A, Niehaus K. The influence of a modified lipopolysaccharide O-antigen on the biosynthesis of xanthan in Xanthomonas campestris pv. campestris B100. BMC Microbiology. 2016;16(1): 93.Background The exopolysaccharide xanthan is a natural product which is extensively used in industry. It is a thickening agent in many fields, from oil recovery to the food sector. Xanthan is produced by the Gram negative bacterium Xanthomonas campestris pv. campestris (Xcc). We analyzed the lipopolysaccharide (LPS) of three mutant strains of the Xcc wild type B100 to distinguish if the xanthan production can be increased when LPS biosynthesis is affected. Results The Xcc B100 O-antigen (OA) is composed of a linear main chain of rhamnose residues with N-acetylfucosamine (FucNAc) side branches at every second rhamnose. It is the major LPS constituent. The O-antigen was missing completely in the mutant strain H21012 (deficient in wxcB), since neither rhamnose nor FucNAc could be detected as part of the LPS by MALDI-TOF-MS, and only a slight amount of rhamnose and no FucNAc was found by GC analysis. The LPS of two other mutants was analyzed, Xcc H28110 (deficient in wxcK) and H20110 (wxcN). In both of them no FucNAc could be detected in the LPS fraction, while the rhamnose moieties were more abundant than in wild type LPS. The measurements were carried out by GC and confirmed by MALDI-TOF-MS analyses that indicated an altered OA in which the branches are missing, while the rhamnan main chain seemed longer than in the wild type. Quantification of xanthan confirmed our hypothesis that a missing OA can lead to an increased production of the extracellular polysaccharide. About 6.3 g xanthan per g biomass were produced by the Xcc mutant H21012 (wxcB), as compared to the wild type production of approximately 5 g xanthan per g biomass. In the two mutant strains with modified OA however, Xcc H28110 (wxcK) and Xcc H20110 (wxcN), the xanthan production of 5.5 g and 5.3 g, respectively, was not significantly increased. Conclusions Mutations affecting LPS biosynthesis can be beneficial for the production of the extracellular polysaccharide xanthan. However, only complete inhibition of the OA resulted in increased xanthan production. The inhibition of the FucNAc side branches did not lead to increased production, but provoked a novel LPS phenotype. The data suggests an elongation of the linear rhamnan main chain of the LPS OA in both the Xcc H28110 (wxcK) and Xcc H20110 (wxcN) mutant strains

Investigating the Potential of a Transparent Xanthan Polymer for Enhanced Oil Recovery: A Comprehensive Study on Properties and Application Efficacy

This study delves into the properties and behavior of xanthan TNCS-ST, a specialized variant designed for enhanced oil recovery (EOR) purposes. A notable aspect of this polymer is its transparency and capability to dissolve in high salt concentrations, notably up to 18% total dissolved solids. Various laboratory methods are employed to assess the polymer’s distinctive traits, including transparency, salt tolerance, and high pyruvylation. These methods encompass preparing xanthan solutions, conducting filtration tests, assessing energy consumption, and measuring rheological properties. The findings highlight the influence of salt concentration on xanthan’s filterability, indicating increased energy requirements for dissolution with higher salt and xanthan concentrations. Additionally, this study observes temperature-dependent viscosity behavior in different solutions and evaluates the shear stability of xanthan. A significant and novel characteristic of TNCS-ST is its high salt tolerance, enabling complete dissolution at elevated salt concentrations, thus facilitating the filterability of the xanthan solution with sufficient time and energy input. Core flooding experiments investigate fluid dynamics within porous rock formations, particularly sandstone and carbonate rocks, while varying salinity. The results underscore the substantial potential of the new xanthan polymer, demonstrating its ability to enhance oil recovery in sandstone and carbonate rock formations significantly. Remarkably, the study achieves a noteworthy 67% incremental recovery in carbonate rock under the high salinity level tested, suggesting promising prospects for advancing enhanced oil recovery applications

Correlation between secondary structures and rheological properties of xanthan polymers

Fjodorova J, Walhorn V, Hublik G, Anselmetti D. Correlation between secondary structures and rheological properties of xanthan polymers. Biophysical Journal . 2022;121(3, Suppl. 1):543A

Establishment, in silico analysis, and experimental verification of a large-scale metabolic network of the xanthan producing Xanthomonas campestris pv. campestris strain B100

Schatschneider S, Persicke M, Watt T, et al. Establishment, in silico analysis, and experimental verification of a large-scale metabolic network of the xanthan producing Xanthomonas campestris pv. campestris strain B100. Journal of Biotechnology. 2013;167(2):123-134

Tuning Xanthan Viscosity by Directed Random Coil-to-Helix Transition

Fjodorova J, Held R, Hublik G, et al. Tuning Xanthan Viscosity by Directed Random Coil-to-Helix Transition. Biomacromolecules. 2022.Xanthan gum is a polysaccharide that is widely used as a thickening agent in numerous food, cosmetic, and technical applications. Therefore, the knowledge of the molecular interplay that builds up and stabilizes water-binding networks is crucial for the optimization of xanthan thickening performance. Using atomic force microscopy, rheometry, and inductively coupled plasma optical emission spectroscopy, we show a clear correlation between xanthan thickening properties and the ability to form characteristic secondary structures as well as the valence and amount of cations coordinated at the polysaccharide side chain. Based on these findings and the Debye–Hückel theory, we derive an ion-interaction model in which divalent cations mediate bridging of adjacent single polymer strands due to chelate-like coordination building stable secondary structures. We furthermore demonstrate in a cation exchange assay that xanthan secondary structures can be modified in a directed and reversible manner, which, in turn, alters its thickening properties

Genome wide transcription start sites analysis of the Xanthomonas campestris pv. campestris B100 with insights into the gum gene cluster directing the biosynthesis of the exopolysaccharide xanthan.

Alkhateeb R, Vorhölter F-J, Rückert C, et al. Genome wide transcription start sites analysis of the Xanthomonas campestris pv. campestris B100 with insights into the gum gene cluster directing the biosynthesis of the exopolysaccharide xanthan. J Biotechnol. 2016;225:18-28

Comparative transcription profiling of two fermentation cultures of Xanthomonas campestris pv. campestris B100 sampled in the growth and in the stationary phase

Alkhateeb R, Vorhölter F-J, Steffens T, et al. Comparative transcription profiling of two fermentation cultures of Xanthomonas campestris pv. campestris B100 sampled in the growth and in the stationary phase. Applied Microbiology and Biotechnology. 2018;102(15):6613-6625.The E -proteobacterium pound Xanthomonas campestris pv. campestris (Xcc) is the producer of the biopolymer xanthan, a polysaccharide which is used as a thickener in numerous industrial applications. In this study, we present a global transcriptome profiling of two Xcc strain B100 cultures obtained from fermentation during the growth phase and the subsequent stationary phase associated with xanthan biosynthesis. During the xanthan production phase, highly abundant transcripts belonged to genes encoding for small RNAs, glycogen biosynthesis, and xanthan export. A total of 1850 (40%) genes were differentially transcribed during the stationary phase where 924 were transcriptionally up-regulated and 926 genes were down-regulated. An overview of differentially transcribed genes includes a significant down-regulation of genes involved in transcription, translation, and amino acid biosynthesis pathways. A group of up-regulated genes was involved in cellular response against oxidative stress, such as those coding for superoxide dismutase and catalase. Genes encoding enzymes involved in nucleotide sugar precursor synthesis of xanthan biosynthesis, such as xanA, galU, and ugd, exhibited a transcription pattern that did not change during the growth and stationary phase. Regarding the transcription pattern of the gum gene cluster that govern xanthan biosynthesis, a significant up-regulation of the genes gumB, gumC, and gumD was observed, while the transcript pools of the genes gumG, gumH, gumI, and gumJ were reduced and those of genes gumE, gumF, gumK, gumL, and gumM remained un-changed during the stationary phase compared to the growth phase. The obtained data represents the first analysis of gene expression patterns under xanthan production conditions and provides the bases for future studies aiming at enhancing xanthan yield

Drivers of soil moisture trends in the Czech Republic between 1961 and 2012

Soil moisture dynamics and their temporal trends in the Czech Republic are forced by various drivers. Our analysis of temporal trends indicates that shifts in drought severity between 1961 and 2012 and especially in the April, May, and June period, which displayed such results as a 50% increase in drought probability during 1961–1980 in comparison to 2001–2012. We found that increased global radiation and air temperature together with decreased relative humidity (all statistically significant at p < 0.05) led to increases in the reference evapotranspiration in all months of the growing season; this trend was particularly evident in April, May, and August, when more than 80% of the territory displayed an increased demand for soil water. These changes, in combination with the earlier end of snow cover and the earlier start of the growing season (up to 20 days in some regions), led to increased actual evapotranspiration at the start of the growing season that tended to deplete the soil moisture earlier, leaving the soil more exposed to the impacts of rainfall variability. These results support concerns related to the potentially increased severity of drought events in Central Europe. The reported trend patterns are of particular importance with respect to expected climate change, given the robustness and consistency of the trends shown and the fact that they can be aligned with the existing climate model projections. Introductio

Refined annotation of the complete genome of the phytopathogenic and xanthan producing Xanthomonas campestris pv. campestris strain B100 based on RNA sequence data

Alkhateeb R, Rückert C, Rupp O, et al. Refined annotation of the complete genome of the phytopathogenic and xanthan producing Xanthomonas campestris pv. campestris strain B100 based on RNA sequence data. Journal of Biotechnology. 2017;253:55-61