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Phenotypic Profiling Reveals that Candida albicans Opaque Cells Represent a Metabolically Specialized Cell State Compared to Default White Cells

View Article: PubMed Central - PubMed

ABSTRACT

The white-opaque switch is a bistable, epigenetic transition affecting multiple traits in Candida albicans including mating, immunogenicity, and niche specificity. To compare how the two cell states respond to external cues, we examined the fitness, phenotypic switching, and filamentation properties of white cells and opaque cells under 1,440 different conditions at 25°C and 37°C. We demonstrate that white and opaque cells display striking differences in their integration of metabolic and thermal cues, so that the two states exhibit optimal fitness under distinct conditions. White cells were fitter than opaque cells under a wide range of environmental conditions, including growth at various pHs and in the presence of chemical stresses or antifungal drugs. This difference was exacerbated at 37°C, consistent with white cells being the default state of C. albicans in the mammalian host. In contrast, opaque cells showed greater fitness than white cells under select nutritional conditions, including growth on diverse peptides at 25°C. We further demonstrate that filamentation is significantly rewired between the two states, with white and opaque cells undergoing filamentous growth in response to distinct external cues. Genetic analysis was used to identify signaling pathways impacting the white-opaque transition both in vitro and in a murine model of commensal colonization, and three sugar sensing pathways are revealed as regulators of the switch. Together, these findings establish that white and opaque cells are programmed for differential integration of metabolic and thermal cues and that opaque cells represent a more metabolically specialized cell state than the default white state.

No MeSH data available.


Related in: MedlinePlus

Metabolic profiling of wild-type white and opaque cells. (A) Cell morphologies of white and opaque cells. (B) Percent active wells (metabolic activity of ≥5) for each substrate group for white and opaque cells at 25°C and 37°C. (C) Heat map of metabolic activities of white and opaque cells grown at 25°C and 37°C in Phenotypic MicroArray (PM) conditions. Metabolic activity is represented on a scale from 0 (no growth [blue]) to 9 (maximum growth [yellow]). Substrate groups are C sources (PM01 and PM02), N and peptide sources (PM03 and PM06 to PM08), P and S sources (P/S) (PM04), supplements (supp) (PM05), osmotic stress and pH substrates (OS/pH) (PM09 and PM10), and chemicals (PM21 to PM25). Average metabolic activities across all conditions for each starting state are shown at the bottom of the heat map. (D) Conditions in which opaque cells grow better than white cells based on white cell/opaque cell (WH/OP) metabolic activity ratios that were ≤0.5.
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fig1: Metabolic profiling of wild-type white and opaque cells. (A) Cell morphologies of white and opaque cells. (B) Percent active wells (metabolic activity of ≥5) for each substrate group for white and opaque cells at 25°C and 37°C. (C) Heat map of metabolic activities of white and opaque cells grown at 25°C and 37°C in Phenotypic MicroArray (PM) conditions. Metabolic activity is represented on a scale from 0 (no growth [blue]) to 9 (maximum growth [yellow]). Substrate groups are C sources (PM01 and PM02), N and peptide sources (PM03 and PM06 to PM08), P and S sources (P/S) (PM04), supplements (supp) (PM05), osmotic stress and pH substrates (OS/pH) (PM09 and PM10), and chemicals (PM21 to PM25). Average metabolic activities across all conditions for each starting state are shown at the bottom of the heat map. (D) Conditions in which opaque cells grow better than white cells based on white cell/opaque cell (WH/OP) metabolic activity ratios that were ≤0.5.

Mentions: Phenotypic MicroArrays provide a high-throughput tool for examining microbial cells under thousands of culture conditions. To assess phenotypic differences between C. albicans white (WH) and opaque (OP) cells (Fig. 1A), we grew both cell types on Phenotypic MicroArray (PM) plates (Biolog) coated with different nutrients and chemical substrates. Growth of white and opaque cells was monitored at 25°C and 37°C for a period of 24 to 48 h. Growth data were analyzed using DuctApe, which weighs cell fitness by combining multiple growth parameters (length of the lag phase, slope of the growth curve, average height of the curve, maximum cell respiration, and area under the curve; see Materials and Methods; also see data in Table S1A in the supplemental material). At the end of the growth period, cells were also analyzed to ascertain whether the induction of filamentous growth or switching between white and opaque forms took place during the experiment (see Materials and Methods).


Phenotypic Profiling Reveals that Candida albicans Opaque Cells Represent a Metabolically Specialized Cell State Compared to Default White Cells
Metabolic profiling of wild-type white and opaque cells. (A) Cell morphologies of white and opaque cells. (B) Percent active wells (metabolic activity of ≥5) for each substrate group for white and opaque cells at 25°C and 37°C. (C) Heat map of metabolic activities of white and opaque cells grown at 25°C and 37°C in Phenotypic MicroArray (PM) conditions. Metabolic activity is represented on a scale from 0 (no growth [blue]) to 9 (maximum growth [yellow]). Substrate groups are C sources (PM01 and PM02), N and peptide sources (PM03 and PM06 to PM08), P and S sources (P/S) (PM04), supplements (supp) (PM05), osmotic stress and pH substrates (OS/pH) (PM09 and PM10), and chemicals (PM21 to PM25). Average metabolic activities across all conditions for each starting state are shown at the bottom of the heat map. (D) Conditions in which opaque cells grow better than white cells based on white cell/opaque cell (WH/OP) metabolic activity ratios that were ≤0.5.
© Copyright Policy - open-access
Related In: Results  -  Collection

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fig1: Metabolic profiling of wild-type white and opaque cells. (A) Cell morphologies of white and opaque cells. (B) Percent active wells (metabolic activity of ≥5) for each substrate group for white and opaque cells at 25°C and 37°C. (C) Heat map of metabolic activities of white and opaque cells grown at 25°C and 37°C in Phenotypic MicroArray (PM) conditions. Metabolic activity is represented on a scale from 0 (no growth [blue]) to 9 (maximum growth [yellow]). Substrate groups are C sources (PM01 and PM02), N and peptide sources (PM03 and PM06 to PM08), P and S sources (P/S) (PM04), supplements (supp) (PM05), osmotic stress and pH substrates (OS/pH) (PM09 and PM10), and chemicals (PM21 to PM25). Average metabolic activities across all conditions for each starting state are shown at the bottom of the heat map. (D) Conditions in which opaque cells grow better than white cells based on white cell/opaque cell (WH/OP) metabolic activity ratios that were ≤0.5.
Mentions: Phenotypic MicroArrays provide a high-throughput tool for examining microbial cells under thousands of culture conditions. To assess phenotypic differences between C. albicans white (WH) and opaque (OP) cells (Fig. 1A), we grew both cell types on Phenotypic MicroArray (PM) plates (Biolog) coated with different nutrients and chemical substrates. Growth of white and opaque cells was monitored at 25°C and 37°C for a period of 24 to 48 h. Growth data were analyzed using DuctApe, which weighs cell fitness by combining multiple growth parameters (length of the lag phase, slope of the growth curve, average height of the curve, maximum cell respiration, and area under the curve; see Materials and Methods; also see data in Table S1A in the supplemental material). At the end of the growth period, cells were also analyzed to ascertain whether the induction of filamentous growth or switching between white and opaque forms took place during the experiment (see Materials and Methods).

View Article: PubMed Central - PubMed

ABSTRACT

The white-opaque switch is a bistable, epigenetic transition affecting multiple traits in Candida albicans including mating, immunogenicity, and niche specificity. To compare how the two cell states respond to external cues, we examined the fitness, phenotypic switching, and filamentation properties of white cells and opaque cells under 1,440 different conditions at 25°C and 37°C. We demonstrate that white and opaque cells display striking differences in their integration of metabolic and thermal cues, so that the two states exhibit optimal fitness under distinct conditions. White cells were fitter than opaque cells under a wide range of environmental conditions, including growth at various pHs and in the presence of chemical stresses or antifungal drugs. This difference was exacerbated at 37°C, consistent with white cells being the default state of C. albicans in the mammalian host. In contrast, opaque cells showed greater fitness than white cells under select nutritional conditions, including growth on diverse peptides at 25°C. We further demonstrate that filamentation is significantly rewired between the two states, with white and opaque cells undergoing filamentous growth in response to distinct external cues. Genetic analysis was used to identify signaling pathways impacting the white-opaque transition both in vitro and in a murine model of commensal colonization, and three sugar sensing pathways are revealed as regulators of the switch. Together, these findings establish that white and opaque cells are programmed for differential integration of metabolic and thermal cues and that opaque cells represent a more metabolically specialized cell state than the default white state.

No MeSH data available.


Related in: MedlinePlus