Project description:The marine Flavobacterium Formosa agariphila KMM 3901T is able to use a broad range of different carbohydrates as growth substrates. This is reflected in the strain’s repertoire of 13 polysaccharide utilization loci (PUL) in total. One PUL – termed as PUL H – is responsible for ulvan degradation, which is a widely distributed, algal-derived polysaccharide. The PUL comprises almost 40 genes, coding for transporters, lyases, glycoside hydrolases or sulfatases, among others. These proteins catalyse the breakdown of ulvan or the uptake of degradation products. A combined application of isotope labeling, subcellular protein fractionation and quantitative proteomics revealed that corresponding PUL encoded proteins were substrate specific up-regulated in ulvan-cultivated cells. The sulphated polysaccharide ulvan also induced the specific expression of proteins necessary for subsequent monosaccharide degradation. Compared to a control (fructose-cultivated cells), expression of PUL H additionally responded to rhamnose, a basic component of ulvan, indicating that this monosaccharide might signal ulvan availability in the environment. Our proteome analyses proofed a substrate specific expression of proteins involved in ulvan utilization and allowed us to deduce a comprehensive degradation pathway for this complex marine polysaccharide.
Project description:A recent algicidal mode indicates that fungal mycelia can wrap and eliminate almost all the co-cultivated algal cells within a short time. However, the regulation of molecular mechanism is rarely understood. Here, proteomic analysis was applied to investigate the algicidal process of Trametes versicolor F21a. Our results showed that 3,754 fungal proteins were identified, among which 2,809 unique proteins could be quantified during the process. 30 isoenzymes with the capacity of degradation biomass, belonging to Glycoside Hydrolases, Auxiliary Activities, Carbohydrate Esterases and Polysaccharide Lyases, were significantly up-regulated, suggesting that these enzymes probably employed synergistic mechanisms in degrading algal cells. Additionally, peptidase, exonuclease, manganese peroxidase and cytochrome c peroxidase were also up-regulated. 10% of the significantly up-regulated proteins were extracellular enzymes. Gene Ontology (GO) and KEGG pathway enrichment analysis demonstrated that the enriched metabolic pathways mainly contained carbon metabolism, selenocompound metabolism, sulfur assimilation and metabolism, as well as several amino acid biosynthesis pathways, which implied that these pathways should play vital roles in the synthesis of needed nutrition for the fungal mycelia via components of algal cells. Moreover, the fungal NmrA-like transcriptional regulator which represses the nitrogen metabolite was also enriched and might be a key regulator in eliminating algal cells
Project description:We set out to investigate the genetic adaptions of the known marine fungus Paradendryphiella salina CBS112865 to the degradation of brown macro-algae, expecting to find a repertoire of carbohydrate active enzymes highly specialized to the degradation of algal polysaccharides. We performed whole genome, transcriptome sequencing and shotgun proteomic analysis of the secretome of P. salina growing on three species of brown algae and under carbon starvation. The genome comparison to close terrestrial fungal relatives, revealed P. salina to have a similar, but reduced carbohydrate active enzyme (CAZyme) profile, except for the presence of three putative alginate lyase 7 genes, most likely acquired via ancient horizontal gene transfer event from a marine bacterium and a polysaccharide lyase 8 gene with similarity to ascomycete chondroitin AC lyases. The proteomic analysis revealed both PL7 and PL8 enzymes to be highly abundant in the algal fermentations together with enzymes necessary for degradation of laminarin, cellulose, lipids and peptides. Our findings indicate that the base CAZyme repertoire of saprobic and plant pathogenic ascomycetes with the necessary addition of alginate lyases provide the fungi with the enzymatic capabilities to thrive on brown algae polysaccharides and even cope with the algal defense mechanisms.
Project description:Dietary fiber degradation is a key function of the human gut microbiota. The aim of this study was to increase our knowledge on the degradation of plant cell wall polysaccharide degradation by a prominent human gut bacterial species, Bacteroides xylanisolvens. The transcriptome analysis of B. xylanisolvens XB1AT revealed the existence of six and two genomic loci dedicated to the degradation of pectins and xylan, respectively. These loci or PUL ("Polysaccharide Utilization Loci") are known to encode enzyme systems in Bacteroides that are specific to a particular polysaccharide. Simple two-way comparisons between pectin or xylan sources (treatment) and glucose or xylose (control), collected during mid- and late-log phase. Three replicates per condition.
Project description:Dietary fiber degradation is a key function of the human gut microbiota. The aim of this study was to increase our knowledge on the degradation of plant cell wall polysaccharide degradation by a prominent human gut bacterial species, Bacteroides xylanisolvens. The transcriptome analysis of B. xylanisolvens XB1AT revealed the existence of six and two genomic loci dedicated to the degradation of pectins and xylan, respectively. These loci or PUL ("Polysaccharide Utilization Loci") are known to encode enzyme systems in Bacteroides that are specific to a particular polysaccharide.
Project description:Macroalgae contribute substantially to primary production in coastal ecosystems. Their biomass, mainly consisting of polysaccharides, is cycled into the environment by marine heterotrophic bacteria (MHB), using largely uncharacterized mechanisms. In Zobellia galactanivorans, we discovered and characterized the complete catabolic pathway for carrageenans, major cell wall polysaccharides of red macroalgae, providing a model system for carrageenan utilization by MHB. We further demonstrate that carrageenan catabolism relies on a multifaceted carrageenan-induced regulon, including a non-canonical polysaccharide utilization locus (PUL) and several distal genes. The genetic structure of the carrageenan utilization system is well conserved in marine Bacteroidetes, but modified in other MHB phyla. The core system is completed by additional functions which can be assumed by non-orthologous genes in different species. This complex genetic structure is due to multiple evolutionary events including gene duplications and horizontal gene transfers. These results allow for an extension on the definition of bacterial PUL-mediated polysaccharide digestion.
Project description:Polysaccharides from macroalgae are important bacterial nutrient source and central biogeochemical component in the oceans. To illuminate the cellular mechanisms of polysaccharide degradation by marine bacteria, growth of Alteromonas macleodii 83-1 on a mix of laminarin, alginate and pectin was characterized using transcriptomics, proteomics and exometabolomics. A. macleodii 83-1 showed two distinct growth stages, with exponential growth during laminarin utilization followed by maintenance during simultaneous alginate/pectin utilization. The biphasic growth coincided with major temporal shifts in gene expression and metabolite secretion, enabling to define major/accessory polysaccharide utilization loci, reconstruct the complete degradation pathways for each polysaccharide, as well as identify temporal phenotypes in other relevant traits. FT-ICR-MS revealed a distinct suite of secreted metabolites for each growth phase, with pyrroloquinoline quinone exclusively produced with alginate/pectin. The finding of substrate-unique phenotypes indicates an exquisite adaptation to polysaccharide utilization with probable relevance for the degradation of macroalgal biomass, which comprises a complex mix of polysaccharides. Moreover, substrate-unique exometabolomes possibly influence metabolic interactions with other community members. Overall, the presence of fine-tuned genetic machineries for polysaccharide degradation and the widespread detection of related CAZymes in global locations indicate an ecological relevance of A. macleodii in marine polysaccharide cycling and bacteria-algae interactions.