BIOTRANSFORMATION OF POLYCYCLIC AROMATIC-HYDROCARBONS BY YEASTS ISOLATED FROM COASTAL SEDIMENTS

Yeast abundance in the sediments of 13 coastal sites in Massachusetts was quantified, and the potential of yeast isolates to biotransform po lycyclic aromatic hydrocarbons (PAHs) was determined. Plate counts of yeasts varied between 10(2) to 10(7) CFU g (dry weight) of sediment-1. The most abundant genera isolated and identified included Candida, Cr yptococcus, Rhodotorula, Torulopsis, and Trichosporon. More than 50% o f the isolates from heavily contaminated sites transformed phenanthren e, as determined by spray-plate screening. The plate counts of phenant hrene-transforming yeasts correlated significantly to the sediment con centrations of phenanthrene. Transformation of [9-C-14]phenanthrene an d [12-C-14]benz[a]anthracene by individual isolates varied greatly, ra nging from 0.15 to 8.15 mumol of PAH g-1 in 120-h incubations. Of the isolated yeasts, Trichosporon penicillatum exhibited the greatest capa city for phenanthrene transformation. The ability to transform PAHs ap pears to be widespread among yeasts in coastal sediments.