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Mutants of Paracoccidioides brasiliensis strain IVIC Pb9 affected in dimorphism
1Centro de Microbiología y Biología Celular, Laboratorio de Micología y Fermentación, Instituto Venezolano de Investigaciones Científicas, Caracas.
Abstract:
Morphological mutants were isolated after nitrosoguanidine treatment of Paracoccidioides brasiliensis strain IVIC Pb9. Two of these mutants, Pb257 and Pb258, developed a typical mycelia at 23 degrees C, however, the yeast cells which developed at 37 degrees C were indistinguishable from those of the parental strain. A third mutant, strain Pb267, was thermosensitive, grew as yeast-like cells at 23 degrees C, but was unable to survive at 37 degrees C. Morphological observations as well as serological and segregation tests confirmed that the mutant strains originated from P. brasiliensis. Cell wall chemical analyses of the mutant strains grown at 23 degrees C indicated the presence of alkali-soluble, acid-insoluble polysaccharides absent in the parental wild-type strain Pb9 grown under the same conditions. The phenotypes shown by the mutant strains may be related to deficiencies in the proper synthesis of cell wall components of the mycelial phase of this fungus.
Insights
Researchers created Paracoccidioides brasiliensis mutants to study fungal cell walls. Some mutants showed altered cell wall composition, suggesting defects in mycelial phase development.
Area of Science:
- Mycology
- Medical Mycology
- Fungal Genetics
Background:
- Paracoccidioides brasiliensis is a fungus causing paracoccidioidomycosis.
- Understanding its morphology and cell wall is crucial for antifungal strategies.
- Chemical composition of the fungal cell wall plays a role in its dimorphism.
Purpose of the Study:
- To isolate and characterize morphological mutants of Paracoccidioides brasiliensis.
- To investigate the cell wall composition of these mutants.
- To explore the relationship between cell wall defects and fungal morphology.
Main Methods:
- Chemical mutagenesis using nitrosoguanidine.
- Culturing mutants at different temperatures (23°C and 37°C) to observe morphology.
- Serological and segregation tests for strain confirmation.
- Chemical analysis of cell wall polysaccharides.
Main Results:
- Two mutants (Pb257, Pb258) showed typical mycelia at 23°C but normal yeast at 37°C.
- One mutant (Pb267) was thermosensitive, growing as yeast-like cells at 23°C but not surviving at 37°C.
- Mutants grown at 23°C exhibited unique alkali-soluble, acid-insoluble polysaccharides not found in the wild-type strain.
Conclusions:
- The observed phenotypes in P. brasiliensis mutants suggest potential deficiencies in cell wall component synthesis during the mycelial phase.
- These findings contribute to understanding the genetic and biochemical basis of fungal dimorphism and cell wall formation.