Toxicity of organotins towards the marine yeastDebaryomyces hansenii.

ABSTRACT

Of nine organotin compounds tested towards the marine yeastDebaryomyces hansenii, only triphenyltin chloride (Ph3SnCl) and mono-, di-, and tributyltin chloride induced significant K(+) release from cells which was symptomatic of viability loss. The general order of toxicity of the butylated compounds was tributyltin chloride (Bu3SnCl) > monobutyltin chloride (BuSnCl3) ≫ dibutyltin chloride (Bu2SnCl2). The overall toxicity of Ph3SnCl was similar to BuSnCl3. Release of K(+) induced by butylated tin compounds or by Ph3SnCl was strongly dependent on the external pH. Maximal toxicity occurred at pH 6.5 for Bu3SnCl, BuSnCl3, and Ph3SnCl, whereas maximal toxicity of Bu2SnCl2 occurred at pH 5.0. Toxicity was decreased above or below these values. The toxicity of BuSnCl3, Bu3SnCl, and Ph3SnCl was reduced at salinity levels approximating to sea water conditions. Prior growth ofD. hansenii in 3% (w/v) NaCl also resulted in reduced sensitivity to Bu3SnCl as evidenced by a decreased rate and extent of K(+) efflux. Bu3SnCl-induced Na(+) release from cells grown in the absence or presence of 3% (w/v) NaCl was low and similar in both cases. It appeared that the monovalent cation was important in the reduction of Bu3SnCl toxicity since Na2SO4 had a similar protective effect as NaCl while CsCl completely prevented K(+) efflux. Thus, the effects of external NaCl were related both to Na(+) and to Cl(-). These results emphasize that cellular and environmental factors influence the toxic effects of organotins and suggests that these compounds may be more effective antimicrobial agents in some environmental niches than in others.