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One small step for a yeast--microevolution within macrophages renders Candida glabrata hypervirulent due to a single point mutation.

Brunke S, Seider K, Fischer D, Jacobsen ID, Kasper L, Jablonowski N, Wartenberg A, Bader O, Enache-Angoulvant A, Schaller M, d'Enfert C, Hube B - PLoS Pathog. (2014)

Bottom Line: Continuous co-incubation of C. glabrata with a murine macrophage cell line for over six months resulted in a striking alteration in fungal morphology: The growth form changed from typical spherical yeasts to pseudohyphae-like structures - a phenotype which was stable over several generations without any selective pressure.Similarly, the Evo mutant significantly increased TNFα production in the brain on day 2, which is mirrored in macrophages confronted with the Evo mutant, but not with the parental wild type.These results indicate that microevolutionary processes in host-simulative conditions can elicit adaptations of C. glabrata to distinct host niches and even lead to hypervirulent strains.

View Article: PubMed Central - PubMed

Affiliation: Integrated Research and Treatment Center, Sepsis und Sepsisfolgen, Center for Sepsis Control and Care (CSCC), Universitätsklinikum Jena, Jena, Germany; Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute Jena (HKI), Jena, Germany.

ABSTRACT
Candida glabrata is one of the most common causes of candidemia, a life-threatening, systemic fungal infection, and is surpassed in frequency only by Candida albicans. Major factors contributing to the success of this opportunistic pathogen include its ability to readily acquire resistance to antifungals and to colonize and adapt to many different niches in the human body. Here we addressed the flexibility and adaptability of C. glabrata during interaction with macrophages with a serial passage approach. Continuous co-incubation of C. glabrata with a murine macrophage cell line for over six months resulted in a striking alteration in fungal morphology: The growth form changed from typical spherical yeasts to pseudohyphae-like structures - a phenotype which was stable over several generations without any selective pressure. Transmission electron microscopy and FACS analyses showed that the filamentous-like morphology was accompanied by changes in cell wall architecture. This altered growth form permitted faster escape from macrophages and increased damage of macrophages. In addition, the evolved strain (Evo) showed transiently increased virulence in a systemic mouse infection model, which correlated with increased organ-specific fungal burden and inflammatory response (TNFα and IL-6) in the brain. Similarly, the Evo mutant significantly increased TNFα production in the brain on day 2, which is mirrored in macrophages confronted with the Evo mutant, but not with the parental wild type. Whole genome sequencing of the Evo strain, genetic analyses, targeted gene disruption and a reverse microevolution experiment revealed a single nucleotide exchange in the chitin synthase-encoding CHS2 gene as the sole basis for this phenotypic alteration. A targeted CHS2 mutant with the same SNP showed similar phenotypes as the Evo strain under all experimental conditions tested. These results indicate that microevolutionary processes in host-simulative conditions can elicit adaptations of C. glabrata to distinct host niches and even lead to hypervirulent strains.

No MeSH data available.


Related in: MedlinePlus

Introduction of a single nucleotide exchange into CHS2 results in increased macrophage damage.Following 24 h co-incubation with macrophages, the CHS2Evo strain, containing the Evo allele of the CHS2 gene, elicited the same increased LDH release from macrophages as the Evo strain. Reintroduction of the wild type CHS2 gene (CHSWT) into the WT strain did not lead to a significant change in its damage potential. (n≥3).
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ppat-1004478-g008: Introduction of a single nucleotide exchange into CHS2 results in increased macrophage damage.Following 24 h co-incubation with macrophages, the CHS2Evo strain, containing the Evo allele of the CHS2 gene, elicited the same increased LDH release from macrophages as the Evo strain. Reintroduction of the wild type CHS2 gene (CHSWT) into the WT strain did not lead to a significant change in its damage potential. (n≥3).

Mentions: To determine whether the introduction of this mutation into the wild type increases its damage capacity to the level of the Evo strain, we measured macrophage damage by the LDH assay. As before, the Evo strain elicited approximately six-fold more damage than the wild type after 24 hours (Fig. 8). Strikingly, wild type C. glabrata harboring the asparagine to lysine substitution (CHSEvo) caused virtually identical macrophage damage as the evolved strain (Fig. 8). In contrast, the control replacement of the CHS2 wild type allele (CHSWT) did not lead to a significant increase in the damage potential after 24 hours. A similar picture emerged when we tested the CHS2 mutant strains in the embryonated chicken egg model (Fig. S4). Here, the CHSWT strain caused the same low final mortality rate as the wild type strain. In contrast, the original Evo and the CHSEvo strain, both carrying the mutated CHS2 allele, showed the same increased virulence in ovo.


One small step for a yeast--microevolution within macrophages renders Candida glabrata hypervirulent due to a single point mutation.

Brunke S, Seider K, Fischer D, Jacobsen ID, Kasper L, Jablonowski N, Wartenberg A, Bader O, Enache-Angoulvant A, Schaller M, d'Enfert C, Hube B - PLoS Pathog. (2014)

Introduction of a single nucleotide exchange into CHS2 results in increased macrophage damage.Following 24 h co-incubation with macrophages, the CHS2Evo strain, containing the Evo allele of the CHS2 gene, elicited the same increased LDH release from macrophages as the Evo strain. Reintroduction of the wild type CHS2 gene (CHSWT) into the WT strain did not lead to a significant change in its damage potential. (n≥3).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214790&req=5

ppat-1004478-g008: Introduction of a single nucleotide exchange into CHS2 results in increased macrophage damage.Following 24 h co-incubation with macrophages, the CHS2Evo strain, containing the Evo allele of the CHS2 gene, elicited the same increased LDH release from macrophages as the Evo strain. Reintroduction of the wild type CHS2 gene (CHSWT) into the WT strain did not lead to a significant change in its damage potential. (n≥3).
Mentions: To determine whether the introduction of this mutation into the wild type increases its damage capacity to the level of the Evo strain, we measured macrophage damage by the LDH assay. As before, the Evo strain elicited approximately six-fold more damage than the wild type after 24 hours (Fig. 8). Strikingly, wild type C. glabrata harboring the asparagine to lysine substitution (CHSEvo) caused virtually identical macrophage damage as the evolved strain (Fig. 8). In contrast, the control replacement of the CHS2 wild type allele (CHSWT) did not lead to a significant increase in the damage potential after 24 hours. A similar picture emerged when we tested the CHS2 mutant strains in the embryonated chicken egg model (Fig. S4). Here, the CHSWT strain caused the same low final mortality rate as the wild type strain. In contrast, the original Evo and the CHSEvo strain, both carrying the mutated CHS2 allele, showed the same increased virulence in ovo.

Bottom Line: Continuous co-incubation of C. glabrata with a murine macrophage cell line for over six months resulted in a striking alteration in fungal morphology: The growth form changed from typical spherical yeasts to pseudohyphae-like structures - a phenotype which was stable over several generations without any selective pressure.Similarly, the Evo mutant significantly increased TNFα production in the brain on day 2, which is mirrored in macrophages confronted with the Evo mutant, but not with the parental wild type.These results indicate that microevolutionary processes in host-simulative conditions can elicit adaptations of C. glabrata to distinct host niches and even lead to hypervirulent strains.

View Article: PubMed Central - PubMed

Affiliation: Integrated Research and Treatment Center, Sepsis und Sepsisfolgen, Center for Sepsis Control and Care (CSCC), Universitätsklinikum Jena, Jena, Germany; Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans Knoell Institute Jena (HKI), Jena, Germany.

ABSTRACT
Candida glabrata is one of the most common causes of candidemia, a life-threatening, systemic fungal infection, and is surpassed in frequency only by Candida albicans. Major factors contributing to the success of this opportunistic pathogen include its ability to readily acquire resistance to antifungals and to colonize and adapt to many different niches in the human body. Here we addressed the flexibility and adaptability of C. glabrata during interaction with macrophages with a serial passage approach. Continuous co-incubation of C. glabrata with a murine macrophage cell line for over six months resulted in a striking alteration in fungal morphology: The growth form changed from typical spherical yeasts to pseudohyphae-like structures - a phenotype which was stable over several generations without any selective pressure. Transmission electron microscopy and FACS analyses showed that the filamentous-like morphology was accompanied by changes in cell wall architecture. This altered growth form permitted faster escape from macrophages and increased damage of macrophages. In addition, the evolved strain (Evo) showed transiently increased virulence in a systemic mouse infection model, which correlated with increased organ-specific fungal burden and inflammatory response (TNFα and IL-6) in the brain. Similarly, the Evo mutant significantly increased TNFα production in the brain on day 2, which is mirrored in macrophages confronted with the Evo mutant, but not with the parental wild type. Whole genome sequencing of the Evo strain, genetic analyses, targeted gene disruption and a reverse microevolution experiment revealed a single nucleotide exchange in the chitin synthase-encoding CHS2 gene as the sole basis for this phenotypic alteration. A targeted CHS2 mutant with the same SNP showed similar phenotypes as the Evo strain under all experimental conditions tested. These results indicate that microevolutionary processes in host-simulative conditions can elicit adaptations of C. glabrata to distinct host niches and even lead to hypervirulent strains.

No MeSH data available.


Related in: MedlinePlus