Project description:Leptosphaeria maculans, causal agent of stem canker disease, colonises oilseed rape (Brassica napus) in two stages: a short and early colonisation stage corresponding to cotyledon or leaf colonisation, and a late colonisation stage during which the fungus colonises systemically and symptomlessly the plant during several months before stem canker appears. To date, determinants of the late colonisation stage are poorly understood; L. maculans may either successfully escape plant defences leading to the stem canker development, or the plant can develop an “adult-stage” resistance reducing canker incidence. To get insight into these determinants, we performed an RNA-seq pilot project comparing fungal gene expression in infected cotyledons and in symptomless and necrotic stems. Despite the low fraction of fungal material in infected stems, enough fungal transcripts were detected and a large portion of fungal genes were expressed, thus validating the feasibility of the approach. Our analysis showed that all avirulence genes previously identified are under-expressed during stem colonisation compared to cotyledon colonisation. A validation RNA-seq experiment was then done to investigate the expression of candidate effector genes during systemic colonisation. 307 "late" effector candidates, under-expressed in the early colonisation stage and over-expressed in the infected stems, were identified. Finally our analysis revealed a link between regulation of expression of effectors and their genomic location: the late effector candidates, putatively involved in the systemic colonisation, are located in gene-rich genomic regions, whereas the "early" effector genes, over-expressed in the early colonisation stage, are located in gene-poor regions of the genome.
Project description:Skin colonisation of varied communities of commensal microorganisms, such as Staphylococcus aureus (SA), Staphylococcus epidermidis (SE) and Staphylococcus capitis (SC) form the microbiome; a necessity for healthy skin. The skin changes characteristic of atopic dermatitis, a common inflammatory skin disease, have been shown to provide a favourable niche for SA colonisation. We utilised a reconstructed human epidermal (RHE) model recapitulating the stratified anatomy of the epidermis on which to test host responses to bacterial colonisation. SA proliferation was significantly inhibited in contrast to that seen with SE at both high and low colonisation loads after 24 hours. These data strongly suggest species specific regulation of staphylococcal growth, which is partially mediated by interaction with the epidermis.
Project description:The aim of this study was to investigate the plastic colonisation process, to identify the active taxa involved in biofilm formation and the mechanisms used to initiate colonisation. To achieve this, a marine plastisphere characterised by active hydrocarbonoclastic genera was used as the inoculum for a short-term microcosm experiment using virgin low-density polyethylene as the sole carbon source. Following incubation for 1 and 2 weeks (representing early and late colonisation, respectively), a taxonomic and comparative metaproteomic approach was used to explore shifts in diversity and function.
Project description:We looked at host gene expression signatures common and specfic to occasionally pathogenic N. meningitidis and commensal N. lactamica. We hypothesise that similar host cell responses during early interactions with N. meningitidis and N. lactamica could inform common mechanisms of colonisation of commensals while differential host cell responses could be capable of altering the outcome of the colonisation process.
Project description:The fungal mutualist Piriformospora indica is colonising barley roots thereby mediating various beneficial effects to its host. The interaction is characterised by an initial biotrophic interaction stage which is followed by a cell death-dependent colonisation phase. We used microarrays to identify the global programme of gene expression during the colonisation process of barley roots by P. indica and to obtain informations into plant defense and metabolic reprogramming.
Project description:Candida albicans is part of the human gastrointestinal (GI) microbiota. To better understand how C. albicans efficiently establishes GI colonisation, we competitively challenged growth of 572 signature-tagged strains (~10% genome coverage), each conditionally overexpressing a single gene, in the murine gut. We identified CRZ2, a transcription factor whose overexpression and deletion respectively increased and decreased early GI colonisation. Using clues from genome-wide expression and gene-set enrichment analyses, we found that the optimal activity of Crz2p occurs under hypoxia at 37°C, as evidenced by both phenotypic and transcriptomic analyses following CRZ2 genetic perturbation. Consistent with early colonisation of the GI tract, we show that CRZ2 overexpression confers resistance to acidic pH and bile salts, suggesting an adaptation to the upper sections of the gut. Genome-wide location analyses revealed that Crz2p directly modulates the expression of many mannosyltransferase- and cell-wall protein-encoding genes, suggesting a link with cell-wall function. We show that CRZ2 overexpression alters cell-wall phosphomannan abundance and increases sensitivity to tunicamycin, suggesting a role in protein glycosylation. Our study reflects the powerful use of gene overexpression as a complementary approach to gene deletion to identify relevant biological pathways involved in C. albicans interaction with the host environment.