Biochemical variation of Cryptococcus neoformans

Schmeding, Kathryn A.; Jong, S. C.; Hugh, Rudolph

doi:10.1007/bf00436523

Cited by 10 publications

(7 citation statements)

References 30 publications

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“…neoformans (serotype D). Although these varieties can be interfertile (29,31,46,47), intervarietal mating results in hybrid strains (serotype AD) that produce largely inviable spores (34). C. neoformans occurs in the environment associated with pigeon guano and certain tree species (9).…”

mentioning

confidence: 99%

Sexual Cycle of Cryptococcus neoformans var. grubii and Virulence of Congenic a and α Isolates

Nielsen

Cox²,

Wang³

et al. 2003

Infect Immun

362

298

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Cryptococcus neoformans is a human-pathogenic fungus that has evolved into three distinct varieties that infect most prominently the central nervous system. A sexual cycle involving haploid cells of a and ␣ mating types has been reported for two varieties (C. neoformans var. neoformans, serotype D, and C. neoformans var. gattii, serotypes B and C), yet the vast majority of infections involve a distinct variety (C. neoformans var. grubii, serotype A) that has been thought to be clonal and restricted to the ␣ mating type. We recently identified the first serotype A isolate of the a mating type which had been thought to be extinct (strain 125.91). Here we report that this unusual strain can mate with a subset of pathogenic serotype A strains to produce a filamentous dikaryon with fused clamp connections, basidia, and viable recombinant basidiospores. One meiotic segregant mated poorly with the serotype A reference strain H99 but robustly with a crg1 mutant that lacks a regulator of G protein signaling and is hyperresponsive to mating pheromone. This meiotic segregant was used to create congenic a and ␣ mating type serotype A strains. Virulence tests with rabbit and murine models of cryptococcal meningitis showed that the serotype A congenic a and ␣ mating type strains had equivalent virulence in animal models, in contrast to previous studies linking the ␣ mating type to increased virulence in congenic serotype D strains. Our studies highlight a role for sexual recombination in the evolution of a human fungal pathogen and provide a robust genetic platform to establish the molecular determinants of virulence.

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mentioning

confidence: 99%

Sexual Cycle of Cryptococcus neoformans var. grubii and Virulence of Congenic a and α Isolates

Nielsen

Cox²,

Wang³

et al. 2003

Infect Immun

362

298

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“…neoformans var. neoformans ) also crossed varietal borders Schmeding et al 1983). Rapid growth at 37°C, characteristic of ~.…”

Section: )mentioning

confidence: 97%

“…because, although sexual isolation is incomplete, 32 to 55% of isolates failed to respond to tester strains used neofprmans var. gattii was reported by Schmeding et al (1983) to occur in~. neoformans var.…”

Section: )mentioning

confidence: 99%

Urease testing and yeast taxonomy

Booth¹,

Vishniac²

1987

Can. J. Microbiol.

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When urease production was assayed by the hydrolysis of [14C]urea, all basidiomycetous yeasts tested, including the Cryptococcus vishniacii complex (previously reported urease negative), produced significant amounts of 14CO2. The Schizosaccharo-mycetaceae were the only urease-positive ascomycetous yeasts tested. Yarrowia lipolytica was urease negative. The stoichiometry of [14C]urea hydrolysis paralleled by Roberts' rapid urea hydrolysis (RUH) test indicated that causes of anomalous results in conventional urease testing include acidification and alkalinization of the test medium by products of endogenous metabolism and autolysis rather than urease activity. Anomalous results also occurred when cells were grown on media containing the chelating agent ethylenediaminetetraacetic acid (EDTA) prior to RUH. The addition of EDTA to a complex natural medium inhibited urease production in all yeasts reportedly growing at 35 °C (and all other yeasts tested), except Filobasidiella (Cr.) neoformans var. neoformans (NIH 12). The RUH test could differentiate at the varietal level: Fil. (Cr.) neoformans var. neoformans was about 10 times more resistant to EDTA in media used for the growth of cells prior to RUH testing than was Fil. neoformans var. bacillispora (Cr. neoformans var. gattii) (NIH 191). Urease production by Fil. neoformans var. bacillispora was specifically restored to half maximal activity by the addition of 22 μM Ni+2 (as NiCl2) to a growth medium containing 0.100 mM EDTA.

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“…PCR products were separated by electrophoresis in 1.4% agarose gel in 1XTBE buffer stained with ethidium bromide at 0.5 ng mL -1 and visualized under UV light. Reference isolates were used as comparison namely ATCC 34871 (serotype A) 29 , RV 45981 (serotype D) 25 , NIH312 (serotype C) 9 and B4546 (serotype B) 9 .…”

Section: Pcr-fingerprintingmentioning

confidence: 99%

Molecular characterization of environmental Cryptococcus neoformans isolated in Vitoria, ES, Brazil

Ribeiro

Ngamskulrungroj

2008

Rev. Inst. Med. trop. S. Paulo

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SUMMARYCryptococcus neoformans is the major cause of fungal meningitis, a potentially lethal mycosis. Bird excreta can be considered a significant environmental reservoir of this species in urban areas, thirty-three samples of pigeon excreta were collected within the city of Vitoria, Brazil. Cryptococcus neoformans was isolated and identified using standard biochemical assays in ten samples. PCR amplification with primer M13 and orotidine monophosphate pyrophosphorylase (URA5) gene-restriction fragment length polymorphism (RFLP) analysis discerned serotypes and genotypes within this species. All isolates were serotype A (C. neoformans var. grubii) and genotype VNI. The two alternative alleles a and a at the mating type locus were determined by PCR amplification and mating assays performed on V8 medium. All isolates were MAT a mating type but only 50% were able to mate in vitro with the opposite mating type MAT a tester strains (JEC20, KN99a and Bt63). This study adds information on the ecology and molecular characterization of C. neoformans in the Southeast region of Brazil.

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Biochemical variation of Cryptococcus neoformans

Cited by 10 publications

References 30 publications

Sexual Cycle of Cryptococcus neoformans var. grubii and Virulence of Congenic a and α Isolates

Sexual Cycle of Cryptococcus neoformans var. grubii and Virulence of Congenic a and α Isolates

Urease testing and yeast taxonomy

Molecular characterization of environmental Cryptococcus neoformans isolated in Vitoria, ES, Brazil

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