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Two Infection Assays to Study Non-Lethal Virulence Phenotypes in C. Albicans using C. Elegans

Published: May 17th, 2021



1Graduate Program in Genetics & Molecular Biology, Emory University, 2Department of Biology, Emory University

Fungal opportunist pathogens can cause life-threatening as well as minor infections, but non-lethal phenotypes are frequently ignored when studying virulence. Therefore, we developed a nematode model that monitors both the survival and reproduction aspects of host to investigate fungal virulence.

While pathogens can be deadly to humans, many of them cause a range of infection types with non-lethal phenotypes. Candida albicans, an opportunistic fungal pathogen of humans, is the fourth most common cause of nosocomial infections which results in ~40% mortality. However, other C. albicans infections are less severe and rarely lethal and include vulvovaginal candidiasis, impacting ~75% of women, as well as oropharyngeal candidiasis, predominantly impacting infants, AIDS patients and cancer patients. While murine models are most frequently used to study C. albicans pathogenesis, these models predominantly assess host survival and are costly, time consuming, and limited in replication. Therefore, several mini-model systems, including Drosophila melanogaster, Danio rerio, Galleria mellonella, and Caenorhabditis elegans, have been developed to study C. albicans. These mini-models are well-suited for screening mutant libraries or diverse genetic backgrounds of C. albicans. Here we describe two approaches to study C. albicans infection using C. elegans. The first is a fecundity assay which measures host reproduction and monitors survival of individual hosts. The second is a lineage expansion assay which measures how C. albicans infection affects host population growth over multiple generations. Together, these assays provide a simple, cost-effective way to quickly assess C. albicans virulence.

Candida albicans is an opportunistic fungal pathogen of humans residing in different niches, including the oral cavity, gastrointestinal, and urogenital tracts1. While typically commensal, C. albicans causes both mucosal and bloodstream infections, the latter of which can be deadly. The severity of C. albicans infection is dependent on host immune function, with immunocompromised individuals more susceptible to infection than healthy individuals1. In addition to host-related factors, C. albicans has several virulence traits which include, hyphae, biofilm formation, and production of se....

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1. Preparatory steps for the experiments

  1. Preparing C. albicans and Escherichia coli cultures
    NOTE: The strains used in this study are listed in Table 1.
    1. Maintain C. albicans and E. coli strains as glycerol stocks at −80 °C.
    2. Using a sterile toothpick, streak desired C. albicans strain onto solid yeast peptone dextrose (YPD) (1% yeast extract, 2% bactopeptone, 2% glucose, 1.5% agar, 0.004% adenine, 0.008% urid.......

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Here we present two assays that measure C. albicans virulence as a non-lethal phenotype using C. elegans as an infection model. The first assay, fecundity, monitors how C. albicans infection impacts single hosts for progeny production and survival. The second assay, lineage expansion, measures how C. albicans infection impacts population growth over multiple generations.

The fecundity assay has multiple measures of h.......

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Here, we present two simple assays that measure fungal virulence. Both assays leverage C. elegans as a host system that includes monitoring for both lethal and non-lethal host phenotypes. For example, fecundity assays investigate the reproductive success of individual infected hosts while also measuring individual survival. The daily monitoring provides not only total brood size, but also reproductive timing, and time of death. The lineage expansion assay was developed as a simplified version of the fecundity as.......

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We thank Dorian Feistel, Rema Elmostafa, and McKenna Penley for their assistance in developing our assays and data collection. This research is supported by NSF DEB-1943415 (MAH).


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NameCompanyCatalog NumberComments
1.5 mL eppendorf microtubes 3810XMillipore SigmaZ606340
100 mm x 15 mm petri platesSigma-AldrichP5856-500EA
15 mL Falcon ConicalsFisher Scientific14-959-70C
50 mL Falcon ConicalsFisher Scientific14-432-22
AdenineMillipore SigmaA8626
Agar (granulated, bacterilogical grade)Apex BioResearch Produces20-248
Aluminum Wire (95% Pt, 32 Gauge)Genesee Scientific59-1M32P
Ammonium ChlorideMillipore Sigma254134
Bacterial Cell SpreaderSP Scienceware21TP50
BactoPeptoneFisher BioReagantsBP1420-500
Disposable Culture Tubes (20 x 150 mm)FIsherBrand14-961-33
Dissection Microscope (NI-150 High Intensity Illuminator)Nikon Instrument Inc.
E. coliCaenorhabditis Genetics CenterOP50
GlucoseMillipore Sigma50-99-7
Medium Petri Dishes (35 X 10 mm)Falcon353001
Metal SpatulaSP Scienceware8TL24
Nematode Growth Media (NGM)Dot ScientificDSN81800-500
Potassium Phosphate monobasicSigmaP0662-500G
Sodium ChlorideFisher ScientificBP358-1
Sodium PhosphateFisher ScientificBP332-500
Streptomycin SulfateThermo-Fisher Scientific11860038
TryptoneMillipore Sigma91079-40-2
UridineMillipore SigmaU3750
Wildtype C. elegansCaenorhabditis Genetics CenterN2
Yeast ExtractMillipore Sigma8013-01-2

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