Project description:Gut microbiome research is rapidly moving towards the functional characterization of the microbiota by means of shotgun meta-omics. Here, we selected a cohort of healthy subjects from an indigenous and monitored Sardinian population to analyze their gut microbiota using both shotgun metagenomics and shotgun metaproteomics. We found a considerable divergence between genetic potential and functional activity of the human healthy gut microbiota, in spite of a quite comparable taxonomic structure revealed by the two approaches. Investigation of inter-individual variability of taxonomic features revealed Bacteroides and Akkermansia as remarkably conserved and variable in abundance within the population, respectively. Firmicutes-driven butyrogenesis (mainly due to Faecalibacterium spp.) was shown to be the functional activity with the higher expression rate and the lower inter-individual variability in the study cohort, highlighting the key importance of the biosynthesis of this microbial by-product for the gut homeostasis. The taxon-specific contribution to functional activities and metabolic tasks was also examined, giving insights into the peculiar role of several gut microbiota members in carbohydrate metabolism (including polysaccharide degradation, glycan transport, glycolysis and short-chain fatty acid production). In conclusion, our results provide useful indications regarding the main functions actively exerted by the gut microbiota members of a healthy human cohort, and support metaproteomics as a valuable approach to investigate the functional role of the gut microbiota in health and disease.
Project description:Chitin is an important fungal cell wall component that is cross-linked to β-glucan for structural integrity. Acquisition of chitin to glucan cross-links has previously been shown to be performed by transglycosylation enzymes in S. cerevisiae, called Congo Red hypersensitive (Crh) enzymes. Here, we characterized the impact of deleting all seven gene members of the crh gene family (crhA-G) in Aspergillus niger on cell wall integrity, cell wall composition and genome-wide gene expression. In this study, we show that the seven-fold knockout strain shows slightly compact plate growth, but no increased sensitivity to cell wall perturbing compounds. Additionally, we found that the cell wall composition of this knockout strain was virtually identical to that of the wild type. In congruence with these data, genome-wide expression analysis revealed very limited changes in gene expression and no signs of activation of the cell wall integrity response pathway. However, deleting the entire crh gene family in cell wall mutants that are deficient in either galactofuranose (ΔugmA) or α-glucan (ΔagsE and ΔagsA, ΔagsE), resulted in a synthetic growth defect and an increased sensitivity towards Congo Red compared the parental strains. Altogether, these results indicate that loss of the crh gene family in A. niger does not trigger the cell wall integrity response in itself, but does play an important role in ensuring cell wall integrity in mutant strains with reduced galactofuranose or α-glucan.
Project description:This project contains raw data, intermediate files and results is a re-analysis of the publicly available dataset from the PRIDE dataset PXD005780. The RAW files were processed using ThermoRawFileParser, SearchGUI and PeptideShaker through standard settings (see ‘Data Processing Protocol’). This reanalysis work is part of the MetaPUF (MetaProteomics with Unknown Function) project, which is a collaboration between EMBL-EBI and the University of Luxembourg. The dataset was selected with the following conditions: 1. It has been made publicly available in PRIDE and focuses on metaproteomics of the human gut; 2. The corresponding metagenomics assemblies were also available from ENA (European Nucleotide Archive) or MGnify. The processed peptide reports for each sample are available to view at the contig level on the MGnify website. In total, the reanalysis identified 15,417 unique proteins from 15 samples.
Project description:Candida albicans is a commensal yeast of the human gut, which is tolerated by the immune system, but has the potential to become an opportunistic pathogen. One way in which C. albicans achieves this duality is through the concealing, or exposure of cell wall associated pathogen-associated molecular patterns (PAMPs) in response to host derived environment cues (pH, hypoxia, lactate). This cell wall remodelling allows C. albicans to evade or hyperactivate the host’s innate immune responses leading to disease. Previously we identified that adaptation of C. albicans to acidic environments, conditions encountered during colonisation of the female reproductive tract, induce significant cell wall remodelling resulting in the exposure of two key fungal PAMPs (glucan and chitin). Here we report that this pH-dependent cell wall remodelling is a highly dynamic process, requiring periods of both cell wall unmasking, with peak PAMP exposure occurring between 2-4 hrs, followed by subsequent PAMP remasking. b-glucan remasking was mediated via the cell density dependent fungal quorum sensing molecule farnesol, while chitin remasking was mediated via a small, heat-stable, non-proteinaceous secreted molecule(s). Transcript profiling identified a core set of 42 genes significantly regulated by pH over time, and linked the transcription factor Efg1p to being the main regulator of chitin exposure through regulation of CHT2. This dynamic cell wall remodelling, influenced innate immune recognition of C. albicans, suggesting that during infection C. albicans can manipulate the host innate immune responses.
Project description:The gut bacterium Coprococcus sp. ART55/1 has been found to encode two genes containing glycoside hydrolase family 9 (GH9) catalytic domains. These genes are hypothesised to impact upon the ability of this bacteria to utilise different carbon sources. To further investigate the role of these genes, as well as the wider transcriptome, Coprococcus sp. ART55/1 was grown on five different carbon sources - beta-glucan, lichenan, cellobiose, glucose and glucomannan - and the transcriptional response was investigated using RNA sequencing.