ISOLATION AND PHYSIOLOGICAL CHARACTERIZATION OF THIOTHRIX SP

Thiothrix CT3 was isolated in pure culture by micromanipulation techni que. The growth of this microorganism was analyzed in autotrophic, het erotrophic and mixotrophic conditions, in a bicarbonate: containing mi neral medium supplemented with thiosulphate and/or acetate. Thiothrix CT3 was able to grow in all the conditions examined: the maximum growt h rates estimated were 1.8, 2.5 and 2.5 d(-1) respectively. The capaci ty of this organism to grow autotrophically, as supposed by Winogradsk y in 1888, is a strong advantage over the other bacteria present in ac tivated sludge, when sulphides are produced or carried by the sewer. B oth the maximum growth rate and growth yield coefficient shown during heterotrophic and mixotrophic growth were comparable, indicating that the simultaneous presence of two substrates (acetate and a reduced sul phur compound) does not give it any particular advantage. The strong p resence of Thiothrix spp. in many plants located in South Italy can be explained by the wide nutritional versatility of this filamentous bac terium.