Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2025.10.13.681985

Role of zinc in growth, stress response and virulence gene expression of pathogenic Mucorale Rhizopus arrhizus

SINGH, R.·Kumari, A.·Kaur, P.·Kaur, J.
View original source ↗Export metadata ↓

Abstract

During COVID-19 pandemic, the cases of mucormycosis increased substantially, with rhino-orbito-cerebral form linked to uncontrolled diabetes being the predominant manifestation. Some clinical and epidemiological studies associated the usage of zinc supplements with the occurrence of COVID-19 associated mucormycosis, but experimental evidence remains limited. This study aimed to elucidate the impact of zinc enrichment on Rhizopus arrhizus, the predominant causative agent of mucormycosis. The effect of zinc supplementation (5 to 150 {micro}M) on fungal growth, metabolic activity, antifungal susceptibility and biofilm formation, along with cell-wall (Congo red), oxidative (hydrogen peroxide) and osmotic (sodium chloride) stress was evaluated in RPMI-1640. Morphological changes were visualized by scanning electron microscopy. Gene expression was monitored by RNA sequencing. Zinc supplementation promoted R. arrhizus growth in a concentration-dependent manner, with the effect being particularly pronounced under less-favorable conditions, such as alkaline conditions resembling the nasal pH of diabetics. Exposure to zinc enhanced the metabolic activity, and partly alleviated the cell-wall and oxidative stress. Susceptibility to amphotericin B and posaconazole was unchanged. Zinc-supplemented cultures over-expressed multiple genes, notably those associated with respiratory electron transport chain, ergosterol biosynthesis, chitosan production, oxidative stress response, mucoricin, high-affinity iron permease, iron transport multi-copper oxidase and ferric-reductase-like protein. Zinc also augmented the growth/metabolism of several other Mucorales but not Aspergillus fumigatus and Candida albicans. The findings suggest that zinc supplementation supports mucoralean growth and enhances the expression of key virulence factors, implying that excessive intake of zinc supplements during COVID-19 pandemic likely contributed to the emergence of mucormycosis. IMPORTANCEMucormycosis remains a highly devastating fungal infection that presented additional challenges during the COVID-19 pandemic. Several risk factors were implicated in the emergence of COVID-19 associated mucormycosis (CAM), including inappropriate corticosteroid usage and COVID-19 associated glycemic imbalance. The excessive intake of nutritional supplements, especially that of zinc, owing to self-medication and over-prescription, was also proposed as a plausible factor in the rise of CAM in many clinical/epidemiological studies. This study experimentally evaluated the potential impact of zinc enrichment on pathogenic Mucorales. The work demonstrates that zinc supplementation supports Rhizopus arrhizus growth, metabolism and stress response, and enhances the expression of key virulence factors, including mucoricin and iron transporters. Notably, the augmentation was specifically observed in pathogenic Mucorales but not Aspergillus fumigatus and Candida albicans. The work provides experimental evidence for the potential association of zinc over-availability with the occurrence of CAM, and strengthens evidence-based therapeutic practices in clinical settings.

Source connections

Explore related subjects

microbiologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

SINGH, R., Kumari, A., Kaur, P., Kaur, J.. 2025-10-14. Role of zinc in growth, stress response and virulence gene expression of pathogenic Mucorale Rhizopus arrhizus. https://doi.org/10.1101/2025.10.13.681985

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

A population-scale landscape of the subgingival microbiome reveals divergent routes to periodontal dysbiosis

Periodontitis is an archetypical mucosal inflammatory disease in which microbiome dysbiosis at the tooth-epithelial interface interacts with host genetic and behavioral risk factors to drive immune-mediated tissue destruction. Although subgingival microbiome compositional shifts are thought to parallel disease severity, microbiome variation at the population-level and its relationship to periodontal clinical phenotypes and disease-modifying factors remain poorly defined. Here, we use unsupervised manifold learning to map the compositional landscape of the subgingival microbiome in 1,355 adults spanning periodontal health to severe periodontitis. We identified eight latent microbiome states organized along a branching continuum from eubiosis to dysbiosis. An intermediate microbial configuration marked ecological destabilization and bifurcation into two distinct periodontitis-associated dysbiotic trajectories, distinguished by links to gingival inflammation and smoking. Although the microbiome trajectories broadly tracked periodontal destruction, a minority of individuals showed discordant microbiome-clinical phenotypes, with some individuals with periodontitis retaining otherwise eubiotic microbiomes enriched for low-abundance pathobionts, while some cases of health or mild disease had highly dysbiotic communities, suggesting distinct host susceptibility. Together, these findings define a population-scale ecological landscape of the subgingival microbiome, reveal divergent trajectories to periodontal dysbiosis, and highlight heterogeneity in the relationship between microbial community structure and clinical disease expression.

microbiology↗
bioRxiv2026

The iron-binding siderophore enterobactin is required for the response of multi-drug resistant Klebsiella pneumoniae to zinc limitation

To persist during infection Klebsiella pneumoniae must overcome nutrient iron and zinc limitation imposed by the host immune system through a process called nutritional immunity. Secreted small molecule siderophores are a major virulence determinant of Klebsiella pneumoniae pathogenesis and are presumed to overcome nutritional immunity by binding iron for bacterial acquisition. In this work, we set out to identify how a multi-drug resistant K. pneumoniae grows in zinc limited environments. Using unbiased transcriptomics, proteomics, and an arrayed transposon screen, we identified that synthesis and uptake of the siderophore enterobactin is required to allow for growth in low zinc conditions. Iron-specific chelators did not replicate this phenotype and addition of supplemental iron through heme in growth media could not complement severe growth defects of enterobactin mutant K. pneumoniae experiencing zinc limitation. Finally, zinc starvation induced enterobactin production independent of the canonical zinc uptake regulator (Zur) transcription factor suggesting an unidentified regulatory mechanism by which Gram-negative pathogens may respond to zinc stress. Together, these studies expand the role of enterobactin beyond iron regulation and highlight a previously unreported link between iron and zinc homeostasis in Klebsiella pneumoniae.

microbiology↗
bioRxiv2026

A microbiota-derived protease links phage susceptibility to host epithelial responses

Bacteriophages are major ecological drivers of gut microbial ecology, yet whether bacterial mechanisms that determine phage susceptibility have consequences for the mammalian host remains poorly understood. Here, we identify dipeptidyl peptidase 11 (Dpp11a), the predominant active serine protease of the prevalent gut commensal Phocaeicola vulgatus, as an unexpected bacterial defence factor. Dpp11a protects against environmental proteases and confers resistance to bacteriophage infection. Metatranscriptomic analyses further reveal increased expression of both dpp11a and P. vulgatus-associated phage transcripts in ulcerative colitis stool samples, indicating that both components of this interaction are transcriptionally active in disease-associated human microbiomes. Using the microfluidic gut-on-a-chip co-culture model HuMiX, we show that the absence of Dpp11 is accompanied by altered epithelial tight-junction remodelling during phage-bacterial infection. Together, our findings reveal that the consequences of bacterial phage defence can extend beyond phage-bacterium interactions to the mammalian epithelium.

microbiology↗