An atypical isolate of Paracoccidioides brasiliensis

The ceja-1 sequence as a potential new molecular marker for Paracoccidioides brasiliensis infection

We have developed a two-step PCR assay that amplifies a region of the ceja-1 sequence that is specific for virulent strains of Paracoccidioides brasiliensis. An internal region of the ceja-1 sequence was chosen for designing primers that were utilised in a single tube heminested PCR protocol to amplify DNA from six virulent strains. PCR specificity was determined by the absence of amplified products with genomic DNA from four non-virulent strains of P. brasiliensis and from eight fungal pathogens, one bacterium, two protozoa, one worm and mouse and human genomic DNA (leucocytes). The fact that the PCR product was only obtained with the genetic material from virulent isolates of P. brasiliensis suggested that this partial amplified sequence might be a marker of virulence for this fungus. The diagnostic potential of this PCR was confirmed by the successful amplification of this fragment with genomic DNA obtained in lymph node aspirate from a patient with paracoccidioidomycosis.

Morphological, Biochemical and Molecular Approaches for Comparing Typical and Atypical Paracoccidioides brasiliensis Strains

We evaluated the morphology of typical and atypical Paracoccidioides brasiliensis strains and the expression of its 43 kDa glycoprotein (GP43). Strains of P. brasiliensis preserved under mineral oil for long periods of time presented different morphological patterns on peptone, yeast-extract and glucose (PYG) agar. The intravenous inoculation in BALB/c mice confirmed that a strain bearing morphological alterations was non-virulent. In contrast, another strain also maintained under mineral oil but which did not exhibit such morphological dysfunction was as virulent as the well characterized Pb 339 and Pb 18 strains. The expression of the main antigen expressed by P. brasiliensis, GP43, was assessed in culture filtrates by western immunoblots. Typical and atypical strains were capable of secreting the glycoprotein, except strain Pb IOC 1059. The identity of the atypical strains was confirmed by PCR using specific primers for gp43, though the single PCR-fragment varied in size for the atypical strains. The PCR fragments from an atypical strain, Pb IOC 1210, and the typical Pb 339 and Pb IOC 3698 strains were sequenced and blasted to the gp43 gene from the Pb 18 strain (GenBank AY005429). These results ensured the identity of the atypical strains as P. brasiliensis, and suggested a relationship between the alteration of morphological differentiation and the virulence factor following storage under mineral oil.

Analysis of the genetic polymorphism of Paracoccidioides brasiliensis and Paracoccidioides cerebriformis "Moore" by random amplified polymorphic DNA (RAPD) and 28S ribosomal DNA sequencing--Paracoccidioides cerebriformis revisited

Our purpose was to compare the genetic polymorphism of six samples of P. brasiliensis (113, 339, BAT, T1F1, T3B6, T5LN1), with four samples of P. cerebriformis (735, 741, 750, 361) from the Mycological Laboratory of the Instituto de Medicina Tropical de São Paulo, using Random Amplified Polymorphic DNA Analysis (RAPD). RAPD profiles clearly segregated P. brasiliensis and P. cerebriformis isolates. However, the variation on band patterns among P. cerebriformis isolates was high. Sequencing of the 28S rDNA gene showed nucleotide conservancy among P. cerebriformis isolates, providing basis for taxonomical grouping, and disclosing high divergence to P. brasiliensis supporting that they are in fact two distinct species. Moreover, DNA sequence suggests that P. cerebriformis belongs in fact to the Aspergillus genus.

Characterization of the Mucor circinelloides life cycle by on-line image analysis

AIMS

The life cycle of the dimorphic fungus Mucor circinelloides was studied in a temperature-controlled flow-through cell, which constitutes an ideal tool when following the development of individual cells, with a view to understanding the growth and differentiation processes occurring in and between the different morphological forms of the organism.

METHODS AND RESULTS

Mycelial growth and the transformation of hyphae into chains of arthrospores were characterized by image analysis techniques and described quantitatively. The influence of the nature (glucose and xylose) and concentration of the carbon source on specific growth rate and hyphal growth unit length were studied. The organism branched more profusely on xylose than on glucose while the specific growth rates determined were rather similar. Methods were developed to study the yeast-like growth phase of M. circinelloides in the flow-through cell, and combined with fluorescent microscopy which allowed new insights to bud formation. Additionally, numbers and distribution of nuclei in arthrospores, hyphae and yeasts were studied.

CONCLUSIONS

The results give essential information on the morphological development of the organism.

SIGNIFICANCE AND IMPACT OF STUDY

Development of any industrial process utilizing this organism will be dependent on the information obtained here for effective process optimization.

Cerebriform colonies of Paracoccidioides brasiliensis isolated from nine-banded armadillos (Dasypus novemcinctus) at room temperature

Twelve isolates of Paracoccidioides brasiliensis generated cerebriform colonies at room temperature on potato glucose agar slants (PDA). These isolates contained abundant chlamydospores and yeast-like cells and are a subset of the 65 isolates obtained from nine-banded armadillos (Dasypus novemcinctus). They grew as a yeast form with typical multiple buddings at 37 degrees C on brain heart infusion agar supplemented with 1% glucose. After replating on PDA and culturing at room temperature for 2 months, the mutants appeared as cottonous colonies, which indicated that the morphological characteristics were unstable.