Program Book - 27th Fungal Genetics Conference

FULL POSTER SESSION ABSTRACTSbehind its continued secretion by white cells is intriguing. One likely candidate is farnesol because opaque cells, unlike white cells, do not accumulatedetectable levels of farnesol. Macrophages are capable of detecting and responding to exogenous farnesol. Earlier our group reported that farnesolstimulates the expression of both pro-inflammatory and regulatory cytokines by mouse macrophage. The production of these warning signals is animportant indicator of how the body ultimately hopes to clear the infection. Others have shown that farnesol suppresses the anti-Candida activity ofmacrophages through its cytotoxic effects, thus making it all the more difficult to eliminate the fungus early in infection. Here we report the in vitro role offarnesol and other known QSM in macrophage chemotaxis and relative phagocytosis of C. albicans.499. The Role of ISW2 for in vitro and in vivo Chlamydospore Production in Candida albicans. Ruvini U. Pathirana 1 , Dhammika H. M. L. P. Navarathna 2 ,David D. Roberts 2 , Kenneth W. Nickerson 1 . 1) School of Biological Sciences, University of Nebraska - Lincoln, Lincoln, NE; 2) Laboratory of Pathology, Centerfor Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD.The production of chlamydospores is an unusual feature in the medically important opportunistic pathogen Candida albicans which is commonly used asan in vitro diagnostic tool. These thick walled spherical structures arise from a filament tip which is termed a suspensor cell. In the process of evolution, itis hard to believe that C.albicans makes a spore that does not contribute to its biology and thus the function of chlamydospores is of interest. Upon carefulobservation of the chronic stage of C.albicans colonization in mouse kidneys, we often find large cells similar in appearance to chlamydospores. Wecharacterized these large cells using sucrose density gradients and compared them with in vitro induced chlamydospores. The in vivo cells had the samebuoyancy and were physiologically similar to in vitro chlamydospores. So we hypothesized that chlamydospores may promote the persistence of thesepathogens during pathogenesis, particularly in kidneys. To test the role of chlamydospores during host infection, we used the wild type strain SC5314 andcreated a ISW2 knock out mutant. An ISW2 knock out had been reported to be completely abolish chlamydospore formation. We found that the ISW2mutant had significantly reduced virulence in mouse model of disseminated candidiasis and also failed to induce chlamydospores in mouse kidneys duringpathogenesis . In vitro studies confirm the ability of these mutants for normal filamentous growth, but they failed to produce typical chlamydospores fromsuspensor cells. However, after three weeks they produced chlamydospore-like structures that differed from normal chlamydospore production by thecomplete absence of suspensor cells. As an essential ATP dependent chromatin remodeling factor in yeasts, ISW2 affects the regulation of transcription,recombination, and DNA repair. Our findings suggest that ISW2 may also down regulate the genes for suspensor cell formation but not the genes forchlamydospore formation indicating that these are two independent processes. Further, our investigation into in vivo role of chlamydospores andsuspensor cells suggest that ISW2 could be a future drug target. Further studies on gene regulation by ISW2 in C.albicans will be paramount to ourunderstanding of development and regulatory steps for chlamydospore formation and their contribution to host infection.500. Nutrient immunity and systemic readjustment of metal homeostasis modulate fungal iron availability during the development of renal infections.Joanna Potrykus 1 , David Stead 2 , Dagmar S Urgast 3 , Donna MacCallum 1 , Andrea Raab 3 , Jörg Feldmann 3 , Alistair JP Brown 1 . 1) Aberdeen Fungal Group,University of Aberdeen, Aberdeen, United Kingdom; 2) Aberdeen Proteomics, University of Aberdeen, Aberdeen, United Kingdom; 3) Trace ElementSpeciation Laboratory, University of Aberdeen, Aberdeen, United Kingdom.Iron is a vital micronutrient that can limit the growth and virulence of many microbial pathogens. Here we show, that in the murine model ofdisseminated candidiasis, the dynamics of iron availability are driven by a complex interplay of localized and systemic events. As the infection progresses inthe kidney, Candida albicans responds by broadening its repertoire of iron acquisition strategies from non-heme iron (FTR1-dependent) to heme-ironacquisition (HMX1-dependent), as demonstrated in situ by laser capture microdissection, RNA amplification and qRT-PCR. This suggested changes in ironavailability in the vicinity of fungus. This was confirmed by 56 Fe iron distribution mapping in infected tissues via laser ablation-ICP-MS, which revealeddistinct iron exclusion zones around the lesions. These exclusion zones correlated with the immune infiltrates encircling the fungal mass, and wereassociated with elevated concentrations of murine heme oxygenase (HO-1) circumventing the lesions. Also, MALDI Imaging revealed an increase in hemeand hemoglobin alpha levels in the infected tissue, with their distribution roughly corresponding to that of 56 Fe. Paradoxically, whilst iron was excludedfrom lesions, there was a significant increase in the levels of iron in the kidneys of infected animals. This iron appeared tissue bound, was concentratedaway from the fungal exclusion zones, and was accompanied by increased levels of ferritin and HO-2. This iron accumulation in the kidney correlated withdefects in red pulp macrophage function and red blood cell recycling in the spleen, brought about by the fungal infection. Significantly, this effect could bereplicated by selective chemical ablation of splenic red pulp macrophages by clodronate. Collectively, our data indicate that systemic events shapemicronutrient availability within local tissue environments during fungal infection. The infection attenuates the functionality of splenic red pulpmacrophages leading to elevated renal involvement in systemic iron homeostasis and increased renal iron loading. Simultaneously, localized nutrientimmunity limits iron availability around foci of fungal infection in the kidney. In response, the fungus modulates its iron assimilation strategies.501. Identification of the gut fungi in humans with nonconventional diets. Mallory Suhr, Heather Hallen-Adams. Food Science and Technology,University of Nebraska-Lincoln, Lincoln, NE.Identification of the microorganisms that establish themselves inside and outside the human body is crucial to explore how the microbiome impactshuman health. The recent Human Microbiome Project provides an initial compilation and identification of the gut microbiome ecosystem. It is wellresearched and understood that a large part of the gastrointestinal microbiota spans across the prokaryotic domain, but few studies have investigated thecontribution of fungi to the human gut microbiome. Factors such as diet, genetics, and environment can play an influential role in explaining whydifferences in microbiota exist between human hosts. Expanding on work from our lab, this study examines the effect of nonconventional diets (e.g.vegetarians, vegans, gluten-free and lactose-free) on the GI tract fungi. DNA from fecal samples of healthy human subjects was isolated and fungal-specificITS primers were used to target fungal DNA to obtain a baseline of data for gut fungi. Candida tropicalis and C. albicans were both detected, with C.tropicalis more prevalent. This relative abundance of C. tropicalis is in keeping with our earlier studies in people with conventional diets, and may be aregional phenomenon.502. The mutational landscape of gradual acquisition of drug resistance in clinical isolates of Candida albicans. Jason Funt 1 , Darren Abbey 7 , Luca Issi 5 ,Brian Oliver 3 , Theodore White 4 , Reeta Rao 5 , Judith Berman 6 , Dawn Thompson 1 , Aviv Regev 1,2 . 1) Broad Institute of MIT and Harvard, 7 Cambridge Center,Cambridge, MA 02142; 2) Howard Hughes Medical Institute, Department of Biology, Massachusetts Institute of Technology, 77 Masscahusetts Ave,Camridge, MA 02140; 3) Seattle Biomedical Research Institute, Seattle, WA; 4) School of Biological Sciences, University of Missouri at Kansas City, MS; 5)Worcester Polytechnic Institute, Department of Biology and Biotechnology, 100 Institute Road, Worcester MA 01609; 6) Tel Aviv University, Ramat Aviv,69978 Israel; 7) University of Minnesota, Minneapolis MN 55455 USA.Candida albicans is both a member of the healthy human microbiome and a major pathogen in immunocompromised individuals1. Infections are most244