Candida causes an estimated half-billion cases of vulvovaginal candidiasis (VVC) every year. VVC is most commonly caused by Candida albicans , which, in this setting, triggers nonprotective neutrophil infiltration, aggressive local inflammation, and symptomatic disease. Despite its prevalence, little is known about the molecular mechanisms underpinning the immunopathology of this fungal infection. In this study, we describe the molecular determinant of VVC immunopathology and a potentially straightforward way to prevent disease. In response to zinc limitation, C. albicans releases a trace mineral binding molecule called Pra1 (pH-regulated antigen). Here, we show that the PRA1 gene is strongly up-regulated during vaginal infections and that its expression positively correlated with proinflammatory cytokine concentrations in women. Genetic deletion of PRA1 prevented vaginal inflammation in mice, and application of a zinc solution down-regulated expression of the gene and also blocked immunopathology. We also show that treatment of women suffering from recurrent VVC with a zinc gel prevented reinfections. We have therefore identified a key mediator of symptomatic VVC, giving us an opportunity to develop a range of preventative measures for combatting this disease.

IntroductionAU : Pleaseconfirmthatallheadinglevelsarerepresentedcorrectly: Candida glabrata (Nakoseomyces glabratus) is a haploid, budding yeast that causes opportunistic nosocomial infections and is garnering increasing attention in line with its changing epidemiological importance. It is a commensal of the human mucosa, particularly oral, gastrointestinal, and vaginal epithelia, which predisposes to infection. The physical disruption of the epithelial layer is a major risk factor for systemic C. glabrata infection, which generally occurs in immunocompromised individuals. C. glabrata appears to lack the brute force traits of other Candida species such as filament formation leading to tissue damage and immune cell lysis but nevertheless leads the non-Candida albicansAU : PleasenotethatasperPLOSstyle; donotusespec species in the number of patients it infects. Infections caused by C. glabrata are of great concern due to their propensity for drug resistance and limited treatment options. This article discusses the intrinsic and acquired factors contributing to C. glabrata's increasing resistance to pharmaceutical intervention.

Drug resistance is a rapidly emerging concern, thus prompting the development of novel therapeutics or combinatorial therapy. Currently, combinatorial therapy targets are based on knowledge of drug mode of action and/or resistance mechanisms, constraining the number of target proteins. Unbiased genome-wide screens could reveal novel genetic components within interaction networks as potential targets in combination therapies. Testing this, in the context of antimicrobial resistance, we implemented an unbiased genome-wide screen, performed in Saccharomyces cerevisiae expressing a Candida glabrata PDR1+ gain-of-function allele. Gain-of-function mutations in this gene are the principal mediators of fluconazole resistance in this human fungal pathogen. Eighteen synthetically lethal S. cerevisiae genetic mutants were identified in cells expressing C. glabrata PDR1+. One mutant, lacking the histone acetyltransferase Gcn5, was investigated further. Deletion or drug-mediated inhibition of Gcn5 caused a lethal phenotype in C. glabrata cells expressing PDR1⁺ alleles. Moreover, deletion or drug-mediated inactivation of Gcn5, inhibited the emergence of fluconazole-resistant C. glabrata isolates in evolution experiments. Thus, taken together, the data generated in this study provides proof of concept that synthetically lethal genetic screens can identify novel candidate proteins that when therapeutically targeted could allow effective treatment of drug-resistant infections. Life threatening infections are an increasing reality. Multi-drug resistant bacteria e.g. MRSA are present in nearly all hospitals, and community acquired TB is often recalcitrant to treatment. Less well known, but causing four to five times more deaths in the UK than MRSA, are fungi in the genus Candida. These are commonly associated with mucosal infections such as “thrush”, but are responsible for > 400,000 life-threatening infections worldwide every year, especially in the immunosuppressed patient population. One of the principle pathogens is Candida glabrata. This fungus grows as a single celled yeast, and alarmingly is highly resistant to both host innate defences and many clinically used antifungal drugs. Even with the best possible medical care, infections with this yeast cause ~50% mortality and alarmingly the incidence of C. glabrata infections is steadily climbing. This demands that novel antifungal therapies are developed that can target drug resistant fungal infections such as C. glabrata. We have identified genes that prevent the growth of fungal cells that express gain-of-function mutations in Pdr1, a key mediator of antifungal resistance in C. glabrata. We also provide proof of concept that targeting a protein essential for Pdr1 function significantly inhibits the emergence of antifungal drug resistance. Thus such an approach could provide a powerful tool in developing treatments for drug resistant infections.

The impact of fungi on human and plant health is an ever-increasing issue. Recent studies have estimated that human fungal infections result in an excess of one million deaths per year and plant fungal infections resulting in the loss of crop yields worth approximately 200 million per annum. Sexual reproduction in these economically important fungi has evolved in response to the environmental stresses encountered by the pathogens as a method to target DNA damage. Meiosis is integral to this process, through increasing diversity through recombination. Mating and meiosis have been extensively studied in the model yeast Saccharomyces cerevisiae, highlighting that these mechanisms have diverged even between apparently closely related species. To further examine this, this review will inspect these mechanisms in emerging important fungal pathogens, such as Candida, Aspergillus, and Cryptococcus. It shows that both sexual and asexual reproduction in these fungi demonstrate a high degree of plasticity.

Antifungal drugs have had a tremendous impact on human health and the yields of crops. However, in recent years, due to usage both in a health setting and in agriculture, there has been a rapid emergence of antifungal drug resistance that has outpaced novel compound discovery. It is now globally recognized that new strategies to tackle fungal infection are urgently needed, with such approaches requiring the cooperation of both sectors and the development of robust antifungal stewardship rationales. In this review, we examine the current antifungal regimes in clinical and agricultural settings, focusing on two pathogens of importance, Candida auris and Aspergillus fumigatus, examining their drivers of antifungal resistance, the impact of dual-use azoles and the impact agricultural practices have on driving the emergence of resistance. Finally, we postulate that a One Health approach could offer a viable alternative to prolonging the efficacy of current antifungal agents.

Though highly efficient at fermenting hexose sugars, Saccharomyces cerevisiae has limited ability to ferment five-carbon sugars. As a significant portion of sugars found in cellulosic biomass is the five-carbon sugar xylose, S. cerevisiae must be engineered to metabolize pentose sugars, commonly by the addition of exogenous genes from xylose fermenting fungi. However, these recombinant strains grow poorly on xylose and require further improvement through rational engineering or evolutionary adaptation. To identify unknown genes that contribute to improved xylose fermentation in these recombinant S. cerevisiae, we performed genome-wide synthetic interaction screens to identify deletion mutants that impact xylose utilization of strains expressing the xylose isomerase gene XYLA from Piromyces sp. E2 alone or with an additional copy of the endogenous xylulokinase gene XKS1. We also screened the deletion mutant array to identify mutants whose growth is affected by xylose. Our genetic network reveals that more than 80 nonessential genes from a diverse range of cellular processes impact xylose utilization. Surprisingly, we identified four genes, ALP1, ISC1, RPL20B, and BUD21, that when individually deleted improved xylose utilization of both S. cerevisiae S288C and CEN.PK strains. We further characterized BUD21 deletion mutant cells in batch fermentations and found that they produce ethanol even the absence of exogenous XYLA. We have demonstrated that the ability of laboratory strains of S. cerevisiae to utilize xylose as a sole carbon source is suppressed, which implies that S. cerevisiae may not require the addition of exogenous genes for efficient xylose fermentation.