A Morphological Mutant of Paracoccidioides brasiliensis Strain IVIC Pb9. Isolation and Wall Characterization

Abstract

A morphological mutant of Paracoccidioides brasiliensis strain IVIC ~b 9 was isolated after treatment of the yeast-like (Y) form with nitrosoguanidine. Colonies of the mutant grown at room temperature did not show the whitish cotton-like morphology typical of the mycelial form of the parental strain. Y-cells were much smaller than those produced by the parent and grew forming chains of different sizes. The main chemical difference in the wall of the Y-form was the replacement of the a-1,3-glucan, typical of the parental strain, by an amorphous 1,3-mannan in the mutant.

α1,3 Glucans Are Dispensable in Aspergillus fumigatus

“…In other fungi, such as S. pombe and C. neoformans, ␣1,3 glucans are essential for yeast morphogenesis (14,26). Similar results were also obtained for other dimorphic pathogenic fungi in which the switch between ␤1,3 glucans and ␣1,3 glucans is associated with the changes between mycelium and yeast forms (15,27). In S. pombe, the content of ␣1,3 glucans is 28%.…”

“…␣1,3 glucans are also a major cell wall component of the yeast form of the human pathogens Paracoccidioides brasiliensis, Histoplama capsulatum, Blastomyces dermatitidis, and Cryptococcus neoformans and of the nonpathogenic model yeast Schizosaccharomyces pombe (14,15,24,25,27). In these species, the concentrations reported vary from 28% in S. pombe to 35 to 46% in the virulent yeast forms (13).…”

The cell wall of fungal human pathogens: Its possible role in host-parasite relationshipsA review

“…Polysaccharides, on the contrary, proved important in such a relationship. Experimental results which supported this idea were obtained using two approaches: a) study of changes in the cell wall composition of the pathogenic yeast form of strain IVIC Pb9 as a function of culture medium composition (148, 151 ); b) isolation of mutants altered in their cell wall structure (144,146,149,150) (Table 5). From these results we proposed (148) a hypothesis by which the mural a-l,3-glucan of P. brasiliensis, resistant to hydrolysis by phagocytes due to the lack of the corresponding enzyme, protects the fungus against host defense mechanisms (Fig.…”

Paracoccidioides brasileensis: Cell wall structure and virulence

“…Treatment of strain IVIC Pb9 (Y form) with N'-methyl-N-nitro-N-nitrosoguanidine (NTG) (30,31) produced a mutant (IVIC Pbl40) with micro-and macroscopical variations with respect to the parental strain. A detailed structure of its cell wall produced the results shown in Table 2.…”

“…Moreover, an amorphous galactomannan is found in the cell wall of the M form. This compound is responsible for the antigenic properties of the cell wall (1).Recent studies (30)(31)(32)(33) suggest that the cell wall does not possess a stable chemical structure but a rather changing one, as a function of the environment in which the fungus is grown. At the same time, the cell wall composition seems to correlate with the degree of virulence of the particular strain.…”