Effects of copper, cadmium and methanol on a Candida boidinii strain

Several species of yeasts are capable of growing on a methanol-containing mediu, even when methanol is the only carbon source. This capability is associated with the induction of several enzymes (i.e. alcohol oxidase, catalase). In all the yeasts studied the oxidation of methaol to formaldehyde is catalyzed by an oxidase. Organisms isolated from environments polluted by heavy metals are often tolerant of those metals. The goal of this preliminary test was to note any difference in growth rate or cell size by testing the effects of methanol with the addition of copper or cadmium at different concentrations. An inoculum of 1 ml of cell culture at a concentration of 5x105 cells/ml was made in a flask with 100 ml of the medium under test: a) 100 ml YNB plus glucose (2% w/v); b) 100 ml YNB plus glucose and copper (at the desired final concentration); c) YNB plus glucose nd cadmium (at the desired final concentration). The sme tests were made using methanol 1.5% (v/v) instead of glucose. After inoculum the culture was incubated in a shaked water-bath for a variable time from 24 h until the reaching of the stationary phase; at this time cellular size was made. Every 24 h cell counts were made using a hematocytometer. Our data show that the association of methanol with heavy metals can cause a variation in the cellular morphology. We noted that the presence of cadmium associate with methanol causes decease in cell size with respect to glucose and cadmium when associated. Furthermore, the association of copper with methanol inhibits cell growth. the more toxic association resulted the copper-methanol, in fact, the yeast candida boidinii, used for our tests, was able to grow only in some of these culture conditions, when using lower copper dosages (30 and 40 μg/ml). Methanol also indices an increase in the lag-period with respect to the growth in glucose as sole carbon source, in fact when using methanol at 3% (v/v) the lag-period was two times the blank. Both alcohols and heavy metals seem to have some toxic effects on cells; furthermore, the association of metals and alcohols seems to have a synergic effect, in fact in this case we have the longest la-period.