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Updated: Jun 24, 2026
Assessing the Putative Anticryptococcal Properties of Crude and Clarified Extracts from Mollusks
Published on: December 2, 2022
Evaluation of laccases and melanization in clinical and environmental Cryptococcus neoformans samples by
Cristiane B Pereira1, Frank L Bueno1, Amanda L T Dias1
1Departamento de Ciências Biológicas, Laboratório de Microbiologia e Imunologia, Universidade Federal de Alfenas, Alfenas, MG, Brazil.
Abstract:
The increased incidence of infections caused by the opportunistic pathogen Cryptococcus neoformans, which mainly affects immunocompromised patients but can also infect immunocompetent individuals, has needed additional studies on this micro-organism's pathogenicity and factors related to virulence, such as enzyme production, for a better understanding of the aetiology of cryptococcosis. The aim of this study was to verify the applicability of non-denaturing PAGE for analysis of laccases by quantification of the amount of melanin pigment produced by clinical and environmental strains of C. neoformans. After incubation of the gel with the substrate L-dopa, strains produced melanin spots of a bright brown to black colour. Quantification of these spots was performed by densitometry analysis and the amount of melanin produced was calculated and compared among the strains. All strains showed laccase activity. Serotype B strains showed a higher melanin intensity than serotype A strains. Over half of the clinical strains (56.2%) showed the lowest melanin intensities, suggesting that melanin production may not be the main virulence factor against host defence. The clinical strain ICB 88 revealed two melanin spots on the gel, indicating the presence of two laccase isoforms. The environmental strains showed the highest values of melanin intensity, which may be related to previous exposure to environmental stress conditions.
Insights
Non-denaturing PAGE effectively analyzes laccase activity in Cryptococcus neoformans by quantifying melanin production. Environmental strains showed higher melanin intensity than clinical strains, suggesting melanin may not be the primary virulence factor.
Area of Science:
- Medical Mycology
- Enzymology
- Molecular Biology
Background:
- Cryptococcus neoformans is an opportunistic pathogen causing cryptococcosis, particularly in immunocompromised individuals.
- Understanding C. neoformans pathogenicity and virulence factors, such as laccase enzyme production, is crucial for disease management.
- Melanin production by C. neoformans is a key factor linked to its virulence.
Purpose of the Study:
- To evaluate non-denaturing polyacrylamide gel electrophoresis (PAGE) for analyzing laccase activity in C. neoformans.
- To quantify melanin pigment produced by clinical and environmental C. neoformans strains.
- To compare laccase activity among different C. neoformans serotypes and origins.
Main Methods:
- Non-denaturing PAGE was employed to separate laccase enzymes.
- Laccase activity was visualized by incubating gels with L-dopa substrate, producing melanin spots.
- Melanin spot intensity was quantified using densitometry analysis.
Main Results:
- All tested C. neoformans strains exhibited laccase activity, indicated by melanin production.
- Serotype B strains displayed higher melanin intensity compared to Serotype A strains.
- Over half of clinical strains (56.2%) showed lower melanin intensity than environmental strains, suggesting melanin may not be the primary virulence factor.
Conclusions:
- Non-denaturing PAGE is a viable method for assessing laccase activity and melanin production in C. neoformans.
- Melanin production levels vary between serotypes and origins, with environmental strains showing higher activity.
- The role of melanin as a primary virulence factor in C. neoformans warrants further investigation, especially in clinical isolates.
