Effect of hydrogen ion concentration and of temperature on the growth of Paracoccidioides brasiliensis in soil extracts.

Abstract

The survival of Paracoccidioides brasiliensis in soil extracts adjusted to various pH values and subjected to different temperatures was investigated. The mycelial phase was more resistant to extreme conditions than the yeast phase. Both phases were inhibited by pH 1·4; the yeast phase did not survive pH 3·0 but many of the mycelial elements were viable. With both phases, an increase in the number of viable particles occurred in the extracts with initial pH values of 7·0 and 5·0. However, growth of the mycelial phase was maintained for longer periods. Both types of elements altered the original pH values of the soil extracts in order to reach slightly acidic values (6·2-6·9).Neither phase survived exposure for 3 weeks at — 20° C. or at 45° C. The mycelial elements tolerated 4° C. and were even able of growth at 15° C. while the yeast cells were more sensitive to the effect of the various temperatures.These results are discussed in relation to the chances that each type of cell would have for survival sapr...