STUDIES ON METAL RESISTANCE SYSTEM IN KLUYVEROMYCES-MARXIANUS

Through preliminary plate tests, Kluyveromyces marxianus was found to be much more resistant to toxic heavy metals compared to a CUP1R strai n of Saccharomyces cerevisiae. Specific growth rate and maximum dry we ights affected by increasing metal concentrations were determined to o btain precise patterns of resistance. Metal biosorption was also monit ored during the course of growth in synthetic media containing respect ive metals at 0.5 mM final concentration. Although Zn- and Co-binding was negligible, as much as 90% of silver, 60% of copper, and 65% of ca dmium were found to be absorbed by the end of active growth. Analysis of the protein profiles of S. cerevisiae and K. marxianus on metal exp osure suggested constitutive production of metallothionein in K. marxi anus. Furthermore, a smaller protein synthesized by K. marxianus on in duction by silver or cadmium accounts for the high resistance of the o rganism to these metals.