The colon microcosm: a novel in vitro model to study Candida albicans colonisation of the human colon

Candida albicans colonises the gastro-intestinal (GI) tract of over 60% of the population. In severely ill or immune compromised patients, this fungus can escape the gut, disseminate through the body and cause systemic disease. Most research in the field has focused on defining traits that contribute directly to virulence; there are comparatively few studies which have addressed how C. albicans colonises and persists in the gut. Furthermore, such studies have typically been performed mouse models devoid of resident GI bacteria, completely neglecting the major impact of the local microbiota on GI colonisation. How, then, does C. albicans persist in the GI tract in the presence of the normal gut microbiota? To address this question, a novel in vitro two-phase anaerobic fermentation system that simulates the human colon microenvironment has been developed. This “colon microcosm” supports the growth of human faecal microbiota in liquid anaerobic colon medium (phase 1) and C. albicans growth on agar plugs which are added to the medium to mimic the epithelial surface (phase 2). The impact of C. albicans upon the faecal microbiota is monitored by examining the planktonic phase (phase 1), whilst the effect of the microbiota on the growth of C. albicans is monitored after extracting C. albicans cells from the agar plugs (phase 2). The results of assays carried out to validate the model will be presented, as will data from pilot studies which illustrate the potentially exploitable impact of the human GI microbiota from healthy individuals on C. albicans growth

Dissection of the Candida albicans class I chitin synthase promoters

We acknowledge financial support from the Biotechnology and Biological Sciences Research Council (10161), Medical Research Council (New Investigator Award to C.A.M.), the European Community FUNGALWALL and SIGNALPATH initiatives and the Wellcome Trust.Peer reviewedPublisher PD

Cell wall stress induces alternative fungal cytokinesis and septation strategies

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Cell wall protection by the Candida albicans class I chitin synthases

Open Access funded by Medical Research Council Acknowledgments We thank Kevin Mackenzie in the Microscopy and Histology Core Facility (Institute of Medical Sciences, University of Aberdeen), and Donna MacCallum for helpful statistical advice. This work was supported by grants from the Wellcome Trust (0868827 and 080088) including a Wellcome Trust Strategic Award (097377) and an Investigator Award to NG (101873), an MRC New Investigator Award to ML (MR/J008230/1) and a PhD scholarship awarded to KP from the Ministry of Sciences and Technology and Chiang Mai University, Thailand. Author contributions are as follows: KP constructed strains, performed the majority of the experiments, analyzed the data and contributed to the preparation of the manuscript. JA produced Fig. S1 using the data from the phosphoproteomic analysis conducted by SP and AB. NG conceived and designed experiments, analyzed data and commented on drafts of the manuscript. ML constructed strains, conceived, designed and performed experiments, analyzed data and wrote the manuscript.Peer reviewedPublisher PD

Human gut bifidobacteria inhibit the growth of the opportunistic fungal pathogen Candida albicans

Open Access via the OUP Agreement Funding: Initial studies were funded from a Wellcome Institutional Strategic Support Fund (ISSF) Seed Corn Award [105625/Z/14/Z]. Thereafter, the research was funded by the Scottish Government’s Rural and Environment Science and Analytical Services (RESAS) division. AJPB was supported by programme grants from the UK Medical Research Council (MR/M026663/1; MR/M026663/2) and by the Medical Research Council Centre for Medical Mycology (MR/N006364/1; MR/N006364/2). Acknowledgements: We thank Dr Donna M. MacCallum for critical reading of the manuscript, the Centre for Genome-Enabled Biology and Medicine at the University of Aberdeen for carrying out the 16S rRNA gene sequencing, and Donna Henderson for GC analysis of bacterial fermentation acids. The authors also acknowledge the support of the Maxwell computer cluster funded by the University of Aberdeen.Peer reviewedPublisher PD

Fungal Chitin Dampens Inflammation through IL-10 Induction Mediated by NOD2 and TLR9 Activation

Funding: JW and NARG thank the Wellcome Trust (080088, 086827, 075470), The Wellcome Trust Strategic Award in Medical Mycology and Fungal Immunology (097377) and the European Union ALLFUN (FP7/2007 2013, HEALTH-2010-260338) for funding. MGN was supported by a Vici grant of the Netherlands Organisation for Scientific Research. AJPB and DMM were funded by STRIFE, ERC-2009-AdG-249793 and AJPB additionally by FINSysB, PITN-GA-2008-214004 and the BBSRC [BB/F00513X/1]. MDL was supported by the MRC (MR/J008230/1). GDB and SV were funded by the Wellcome Trust (086558) and TB and MK were funded by the Deutsche Forschungsgemeinschaft (Bi 696/3-1; Bi 696/5-2; Bi 696/10-1). MS was supported by the Deutsche Forschungsgemeinschaft (Sch 897/1-3) and the National Institute of Dental and Craniofacial Research (R01 DE017514-01). TDK and RKSM were funded by the National Institute of Health (AR056296, AI101935) and the American Lebanese Syrian Associated Charities (ALSAC). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD

Crosstalk between the calcineurin and cell wall integrity pathways prevents chitin overexpression in Candida albicans

Funding Information: We thank Carol Munro for helpful discussions during the research, Raif Yuecel, Elizabeth Adams, Linda Duncan, Barry Lewis and Kimberley Sim for assistance with FACS at Aberdeen Cytometry Core Facility, and Yang Meng and Dominique Sanglard with help in construction of mutants. We also thank Linghuo Jiang, David Soll, Jes?s Pla, Jan Quinn, Terry Roemer and Joseph Heitman for mutant strains. N.A.R.G. acknowledges support from the Wellcome Trust [Senior Investigator (101873/Z/13/Z), Collaborative (200208/A/15/Z and 215599/Z/19/Z) and Strategic (097377/Z11/Z) Awards] and from the Medical Research Council Centre for Medical Mycology (MR/N006364/2). This work was also supported by a Marie Curie FP7-PEOPLE-ITN-2008 grant (MB004 RGE0655 ARIADNE) and by a Wellcome Trust project grant (086827). Open access funding provided by University of Exeter. Deposited in PMC for immediate release.Peer reviewedPublisher PD

The Viscoelastic Properties of the Fungal Cell Wall Allow Traffic of AmBisome as Intact Liposome Vesicles

NARG thanks The Wellcome Trust (080088, 086827, 075470, 099215 & 097377) and MRC Centre for Medical Mycology (MR/N006364/1) and acknowledges financial support from Gilead Sciences for a studentship and grant IX-EU-131-0262. Dr. Linda Soo Hoo and Tark Bunch of Gilead provided expert technical assistance in liposomal sample preparations and GF provided gold labelled test articles. JAM is funded in part from a research grant from Gilead Sciences Inc. ML was supported by the MRC (MR/J008230/1). AC was supported in part by 5R01HL059842, 5R01AI033774, 5R37AI033142, and 5R01AI052733. We thank Debbie Wilkinson and Kevin McKenzie at the Imaging Core Facility at the University of Aberdeen for expert assistance with TEM.Peer reviewedPublisher PD

Recognition and blocking of innate immunity cells by Candida albicans chitin

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Adaptation of Candida albicans to environmental pH induces cell wall remodelling and enhances innate immune recognition

Candida albicans is able to proliferate in environments that vary dramatically in ambient pH, a trait required for colonising niches such as the stomach, vaginal mucosal and the GI tract. Here we show that growth in acidic environments involves cell wall remodelling which results in enhanced chitin and β-glucan exposure at the cell wall periphery. Unmasking of the underlying immuno-stimulatory β-glucan in acidic environments enhanced innate immune recognition of C. albicans by macrophages and neutrophils, and induced a stronger proinflammatory cytokine response, driven through the C-type lectin-like receptor, Dectin-1. This enhanced inflammatory response resulted in significant recruitment of neutrophils in an intraperitoneal model of infection, a hallmark of symptomatic vaginal colonisation. Enhanced chitin exposure resulted from reduced expression of the cell wall chitinase Cht2, via a Bcr1-Rim101 dependent signalling cascade, while increased β-glucan exposure was regulated via a non-canonical signalling pathway. We propose that this “unmasking” of the cell wall may induce non-protective hyper activation of the immune system during growth in acidic niches, and may attribute to symptomatic vaginal infection