Encelin: a fungal growth inhibitor.

A known sesquiterpene lactone, encelin, isolated from the Mexican species Montanoa speciosa (Compositae), was assayed for biocidal activity on fungal cells of Mucor rouxii. The results indicate that encelin has a determining action on growth and the morphogenetic process of fungal cells.

Effects of selected synthetic compounds on growth of Mucor rouxii.

The in vitro activity of four synthetic compounds was tested on fungal cells from Mucor rouxii. The compounds included phenylenediamine, two phenolamines, and quinone. At the concentrations tested (10(-2)-10(-4)M) the compounds exhibited antifungal activity, with the exception of quinone. On the basis of their effects on spore germination, and development of hyphae, phenylenediamine was the more active. The mechanism of action of the compounds is still unknown, but hyphae show morphological alterations and disturb the distribution of calcofluor in the cell wall. This suggests variations in the genesis of the cell wall.

Analysis of Sec 19-1 mutant of Saccharomyces cerevisiae.

Saccharomyces cerevisiae Sec 19-1 cells are secretion mutants defective at 37 degrees C. The cells were analysed in order to ascertain the effect of mutation temperature on cell wall formation. At the restrictive temperature of 37 degrees C, the Sec 19-1 mutants had 37 micrograms/mg N-acetylglucosamine in the wall cells, while the wild type S. cerevisiae showed 84 micrograms/mg hexosamine. The mutants Sec 19-1 showed a maximum activity of chitin synthetase of 0.113 nmoles/min/ml, and the activity increased to 0.33 nmoles/min/ml in the wild type cells. On the other hand, variations of chitin distribution in the wall cells occurred at the restrictive temperature, but changes in actin organization were not evident. The results indicated that the mutation caused variations in the levels of N-acetylglucosamine and chitin synthetase, as well as in cell wall chitin distribution.

[Characterization fo mycelial mutants of Mucor rouxii]. / Caracterización de mutantes miceliales de Mucor rouxii.

The consequences of two different mutations induced with N-methyl-N-nitrosoguanidine (Strain G1) and Trifluoperazine resistance (Strain G5) in Mucor rouxii, were studied. Mutants were stable and exhibited mycelial morphology in aerobiosis. Mutants cells exhibit phenotypic characteristics of slow-growing. The mutants G1 and G5 cultures showed 16.8% and 35.3% of reduction of the growth relative to parental strain. Morphologically mycelia of mutants cell were indistinguishable from wild-type cells, except from reduction in extension and branching of hyphal that has the mutant G5. Calcofluor and FITC-Concanavalin A were used to study the distribution of new cell-wall polymers i.e. Chitin, glucans. The two G1 and G5 strains showed a uniform distribution of fluorescence over the cell surface, indicating that active deposition of new-wall material has occurred. Cellular proteins of mutants and parental strains were labeled with 14C-aminoacid mixture. The proteins pattern revealed that the majority of polypeptides synthesized by parental strain were also synthesized by mutants. It is evident the synthesis preferential of peptides with apparent M(r) > 92K, 60K, 50K, 43K, 38K and 25K. These results indicated that the primary defect of the mutation was not on cellular differentiation. It discuss phenotypic and biochemistry characteristics from mutants.

[Inhibition of Mucor rouxii growth by synthetic substances]. / Inhibición del crecimiento de Mucor rouxii por substancias sintéticas.

Mucor rouxii cells were used to examine the possible antimycotic activities of four substances: phenolamines, phenylendiamine and quinone. These substances are original structures recently synthesized. Assays in plates showed that 10(-2) M of phenolamines and phenylendiamines give rise to halos of growth inhibition. Assays in liquid media using 10(-4) M of substances showed 100% inhibition of spore germination. Specifically, the phenylendiamine showed 49% inhibition on development of mycelium. In these cells the calcofluor distribution changes, suggesting alterations in cell wall. No inhibition of growth was found using the quinone. The activity for substances were evaluated using standard antifungal benomyl. On this basis, the substance phenylendiamine it is an antimycotic active. The mechanism of action is not presently known.

Actin in Mucor rouxii.

Rhodamine-conjugated phalloidin was used to analyze the actin distribution during hyphal formation in Mucor rouxii. The occurrence of actin patches in the cortical region of the cells was seen in the initial stages of growth. A fungal 43 kDa protein was isolated by affinity chromatography on DNase I-sepharose. This peptide was identified on immunoblots when polyclonal antibodies against rabbit muscle actin were used as a probe. These results indicate: (1) that changes in actin localization accompany the hyphal development and (2) the fungal 43 kDa protein shares properties that are common to muscle actin.