Competition between n-alkane-assimilating yeasts and bacteria during colonization of sandy soil microcosms

An n-alkane-assimilating strain of Candida tropicalis was selected in sandy soil inoculated with microorganisms from contaminated sites. Competition e xperiments with n-alkane utilizers from different strain collections confir med that yeasts overgrow bacteria in sandy soil. Acidification of the soil is one of the colonization factors useful for the yeasts. It can be counter acted by addition of bentonite, a clay mineral with high ion exchange capac ity, but not, however, by kaolin. Strains of different yeast species showed different levels of competitiveness. Strains of Arxula adeninivorans. Cand ida maltosa, and Yarrowia lipolytica overgrew strains of C. tropicalis, C. shehatae or Pichia stipitis. Two strains of C. maltosa and Y. lipolytica co existed during several serial transfers under microcosm conditions.