Loss of Arp1, a putative actin-related protein, triggers filamentous and invasive growth and impairs pathogenicity in Candida albicans

DNA damage repair factor Rad18 controls virulence partially via transcriptional suppression of genes HWP1 and ECE1 in Candida albicans

DNA damage repair is a crucial cellular mechanism for rectifying DNA lesions arising during growth and development. Among the various repair pathways, postreplication repair (PRR) plays a pivotal role in resolving single-stranded gaps induced by DNA damage. However, the contribution of PRR to virulence remains elusive in the fungal pathogen Candida albicans (C. albicans). In this study, we investigated the role of Rad18, a critical component of PRR, in DNA damage response and virulence in C. albicans. We observed that deletion of RAD18 in C. albicans resulted in heightened sensitivity to DNA damage stress. Through deletion of specific internal domains coupled with spot assay analysis, we show that the internal RING and SAP domains play essential roles in DNA damage response, whereas the ZNF domain was less important. Surprisingly, the lack of Rad18 in C. albicans resulted in heightened intracellular survival within macrophages and elevated virulence in the Galleria mellonella model. RNAseq analysis revealed that loss of Rad18 upregulated the transcription of genes encoding transporters and oxidoreductases, as well as virulence genes, including HWP1 and ECE1. Suppression of the transcription of these virulence genes in the RAD18 deletion strain by a dCas9-mediated CRISPRi system reversed this increased virulence. Taken together, these data demonstrate that Rad18 plays a significant role in virulence partially through transcriptional suppression of virulence genes HWP1 and ECE1 in C. albicans. Our findings provide valuable insights into the intricate relationship between DNA damage response and virulence in C. albicans.

Occidiofungin inhibition of Candida biofilm formation on silicone elastomer surface

IMPORTANCE

Candida are opportunistic fungal pathogens with medical relevance given their association with superficial to life-threatening infections. An important component of Candida virulence is the ability to form a biofilm. These structures are highly resistant to antifungal therapies and are often the cause of treatment failure. In this work, we evaluated the efficacy of the antifungal compound, occidiofungin, against Candida biofilms developed on a silicone surface. We demonstrate that occidiofungin eliminated cells at all stages of biofilm formation in a dose-dependent manner. Consistent with our understanding of occidiofungin bioactivity, we noted alterations to actin organization and cell morphology following antifungal exposure. Given the challenges associated with the treatment of biofilm-associated infections, occidiofungin exhibits potential as a therapeutic antifungal agent in the future.

Dimorphism of Candida tropicalis and its effect on nitrogen and phosphorus removal and sludge settleability

Candida tropicalis PNY, a novel dimorphic strain with the capacity of simultaneous carbon, nitrogen and phosphorus removal in anaerobic and aerobic conditions, was isolated from activated sludge. Dimorphism of C. tropicalis PNY had effect on removing nitrogen and phosphorous and slightly affected COD removal under aerobic condition. Sample with high hypha formation rate (40 ± 5%) had more removal efficiencies of NH₄⁺-N (50 mg/L) and PO₄^3--P (10 mg/L), which could achieve 82.19% and 97.53%, respectively. High hypha cells dosage exhibited good settleability and filamentous overgrowth was not observed. According to label-free quantitative proteomics assays. Up-regulated proteins involved in the mitogen-activated protein kinase (MAPK) pathway indicated the active growth and metabolism process of sample with high hypha formation rate (40 ± 5%). And proteins concerning about glutamate synthetase and SPX domain-contain protein explain for the nutrient removal mechanism including assimilation of ammonia and polyphosphates synthesis.

Transcriptional Profiling of the Candida albicans Response to the DNA Damage Agent Methyl Methanesulfonate

The infection of a mammalian host by the pathogenic fungus Candida albicans involves fungal resistance to reactive oxygen species (ROS)—induced DNA damage stress generated by the defending macrophages or neutrophils. Thus, the DNA damage response in C. albicans may contribute to its pathogenicity. Uncovering the transcriptional changes triggered by the DNA damage—inducing agent MMS in many model organisms has enhanced the understanding of their DNA damage response processes. However, the transcriptional regulation triggered by MMS remains unclear in C. albicans. Here, we explored the global transcription profile in response to MMS in C. albicans and identified 306 defined genes whose transcription was significantly affected by MMS. Only a few MMS-responsive genes, such as MGT1, DDR48, MAG1, and RAD7, showed potential roles in DNA repair. GO term analysis revealed that a large number of induced genes were involved in antioxidation responses, and some downregulated genes were involved in nucleosome packing and IMP biosynthesis. Nevertheless, phenotypic assays revealed that MMS-induced antioxidation gene CAP1 and glutathione metabolism genes GST2 and GST3 showed no direct roles in MMS resistance. Furthermore, the altered transcription of several MMS—responsive genes exhibited RAD53—related regulation. Intriguingly, the transcription profile in response to MMS in C. albicans shared a limited similarity with the pattern in S. cerevisiae, including COX17, PRI2, and MGT1. Overall, C. albicans cells exhibit global transcriptional changes to the DNA damage agent MMS; these findings improve our understanding of this pathogen’s DNA damage response pathways.