IRON-OXIDIZING AUTOTROPHS AND ACIDOPHILIC HETEROTROPHS FROM URANIUM-MINE ENVIRONMENTS

This communication concerns the bacteria recovered from bioleachate an d tailings effluent samples from two-uranium mines in Ontario, Canada. Thirty-four iron-oxidizing autotrophs purified from bioleachate sampl es are described with respect to their colony morphology on ISP agaros e; three distinct colony types were evident AIL of the isolates also g rew in a colloidal sulfur medium and were thus designated as Thiobacil lus ferrooxidans. Three successive streak plates were used to eliminat e the associated vibrioid cells of Leptospirillum ferrooxidans. In add ition, 60 acidophilic heterotrophs purified from bioleachate and taili ngs effluent samples are described with respect to their colony morpho logy on amTS agar; 13 distinct types were evident. Thirty-six of these were examined for growth in amTS broth (pH 3.0 and 6.0), AGY broth (p H 3.0 and 6.0), and sulfur medium, on which basis they were subdivided into acid tolerants, acidophiles, acidotrophs, and sulfur oxidizers. Eight of the isolates were Thiobacillus acidophilus as indicated by th eir ability to grow on sulfur. Thirteen of the 28 non-sulfur-oxidizing acidophilic heterotrophs displayed nutritional characteristics, colon y morphologies, and cellular morphologies similar to Acidiphilium spec ies.