Mannans are components of the fungal wall attached to proteins via N- or O-linkages. In Candida albicans, Och1 is an α1,6-mannosyltransferase that adds the first mannose unit to the N-linked mannan outer chain; whereas Pmr1 is an ion pump that imports Mn²⁺ into the Golgi lumen. This cation is the cofactor of Golgi-resident mannosyltransferases, and thus Pmr1 is involved in the synthesis of both N- and O-linked mannans. Since we currently have limited information about the genetic network behind the Candida tropicalis protein mannosylation machinery, we disrupted OCH1 and PMR1 in this organism. The C. tropicalis pmr1Δ and och1Δ mutants showed increased doubling times, aberrant colony and cellular morphology, reduction in the wall mannan content, and increased susceptibility to wall perturbing agents. These changes were accompanied by increased exposure of both β1,3-glucan and chitin at the wall surface of both mutant strains. Our results showed that O-linked mannans are dispensable for cytokine production by human mononuclear cells, but N-linked mannans and β1,3-glucan are key ligands to trigger cytokine production in a co-stimulatory pathway involving dectin-1 and mannose receptor. Moreover, we found that the N-linked mannan core found on the surface of C. tropicalis och1Δ null mutant was capable of inducing cytokine production; and that a mannan-independent pathway for IL-10 production is present in the C. tropicalis-mononuclear cell interaction. Both mutant strains showed virulence attenuation in the Galleria mellonella and the mouse model of systemic candidiasis. Therefore, mannans are relevant for cell wall composition and organization, and for the C. tropicalis-host interaction.

WhileC. albicansremains the most clinically significantCandidaspecies,C. parapsilosisis an emerging pathogen with increased affinity to neonates. Syk/CARD9 signaling is crucial in immunity toC. albicans, but its role inin vivoresponses to other pathogenicCandidaspecies is largely unexplored.

The best known Microdochium spp. are important pathogens of small-grain cereals and/or endophytes of diverse monocot hosts. This study is the first report of M. majus isolated from asymptomatic grapevine tissues. It was hypothesised that this M. majus strain, CBS 152328, was an endophyte and an antagonist of some fungal pathogens of grapevine. Microscopic examinations revealed that this strain was a necrotrophic mycoparasite of Botrytis cinerea. This was demonstrated in the confrontation zones of dual cultures of M. majus and B. cinerea, and also on the surface of co-inoculated grape leaf discs and germinated wheat grains. Pathogenicity tests indicated that M. majus can colonise both grape leaf discs and germinated wheat, but it only damaged wheat. When co-inoculated with B. cinerea onto grape leaf discs, the M. majus strain CBS 152328 suppressed its mycohost on grape tissues and prevented leaf necrosis caused by B. cinerea. In addition to the parasitism, M. majus also showed mild antibiosis against B. cinerea, as well as a defence elicitor effect on grape leaf discs. This work is the first report of the mycoparasitic behaviour of M. majus, in addition to its first isolation from a dicot host.

In recent years, microbiome studies revealed that Candida species are common colonisers of the human skin. The distribution of species however varies greatly. Although C. parapsilosis is more likely to resemble skin commensals, opinions are divided, and discrepancies are present regarding C. albicans, that is also often associated with cutaneous candidiasis. Therefore, we aimed to thoroughly assess the nature of skin epithelial cell - Candida interactions. To study species-specific host responses, we examined internalization, cytokine and metabolic responses in different keratinocytes (HaCaT, HPV-KER) along with host cell damage following fungal stimuli. To rigorously examine yeast-keratinocyte interactions, we applied two distinct isolates of both C. albicans (SC5314, WO-1) and C. parapsilosis (GA1, CLIB214). Comparison of the two fungi's virulence revealed that while C. albicans effectively adheres to human keratinocytes and causes subsequent damage, C. parapsilosis is unable to establish lasting physical contact and causes less harm. In terms of keratinocyte response, both cell lines showed significantly enhanced cellular (internalization), humoral (IL-6, IL-8) and metabolic responses (2-ketoglutaric acid, citric acid, threorine, hypotaurine) to C. albicans strains, while those towards C. parapsilosis remained relatively low or similar to the control condition. Under certain conditions strain preference was also detected. Of the two cell lines, HPV-KER was more sensitive, as besides interspecies differences, intraspecies differences were also measurable. These results suggest that C. albicans triggers an enhanced antifungal response, thus does not closely resemble skin commensals, like C. parapsilosis. Furthermore, HPV-KER might serve as a more applicable tool for studying keratinocyte antifungal responses.

Phaeomoniella chlamydospora (Pch) is a pioneer pathogen of esca, one of the most destructive grapevine trunk diseases worldwide. A recent work suggests that acetate may act as a quorum-sensing (QS) molecule in Pch, promoting biofilm formation in a concentration-dependent manner. However, the broader influence of acetate on virulence-associated traits remains unexplored. In this study, three Pch isolates were cultured under increasing sodium acetate concentrations (0–100 mM) and assessed for pigmentation, extracellular enzyme activities (amylase, cellulase, protease, esterase, and pectinase), phenolic compound-degrading capacity, and antibacterial activity against a grapevine-associated Pseudomonas sp. isolate. Pigmentation, as well as amylase and cellulase activities, were significantly increased at low acetate supplement levels (6.25–12.5 mM), while esterase activity was unaffected. The expression of these traits decreased above 25 mM acetate supplementation. Phenolic compound degradation capacity, antibacterial efficacy, as well as protease and pectinase activities progressively suppressed at all acetate concentrations. These results indicate that acetate concentration modulates multiple virulence-associated phenotypes of Pch in vitro. Based on these patterns, we propose a hypothetical model in which acetate-dependent phenotypic changes may reflect a shift between establishment-associated activities and reduced extracellular activity at higher acetate levels. This model remains to be validated by mechanistic and in planta infection-based studies.