Search

Tolerance and adaptation to heavy metals of Desulfovibrio- and Desulfotomaculum-strains of different origin have been investigated in enrichment cultures under different conditions of sulphate supply. Three groups of low, medium, and high toxicity were found with As, V, and Mo in the first, Ni, Sb, Co, and Hg in the second, and Cd, Zn, U, and Cu in the third group. If the SO"4-supply was restricted to heavy metal sulphates with a relation of 1:1 of heavy metal- and SO"4 -ions (2:3 with Sb2(SO4)3) the tolerance was somewhat lowered. Adaptation to higher concentrations of heavy metals was possible, if the strains had not yet been exposed and adapted to higher concentration levels at their natural habitats. The tolerance range of desulfurizers has been compared with the tolerance range of different biochemical types of microorganisms.

Eine Methode wird beschrieben, die es gestattet, unter Verwendung der Stempelplattentechnik nach LEDERBERG eine gemischte Bakterienpopulation quantitativ in Gruppen hinsichtlich ihres Wachstumsverhaltens gegenuber verschiedenen Salzkonzentrationen aufzugliedern. Sie erfordert weniger Arbeits- und Materialaufwand als bisher verwendete Methoden. Die Methode wurde auf drei verschiedene naturliche Standorte angewendet: Meerwasser, Fluswasser und ein kleines flaches, stehendes, salzhaltiges Gewasser. Sie erscheint im Prinzip auch fur die Aufgliederung einer Mischpopulation hinsichtlich der Beeinflussung des Wachstums durch andere Faktoren geeignet.

Besides leaching of sulfidic ores with thiobacilli, a second way of microbial leaching is tested with carbon-heterotrophic fungi and bacteria for those types of ores, where thiobacilli fail to work. The active agents are metabolic products, f. i. organic acids, which are released into the medium producing water soluble compounds with heavy metals A screening method is described for recognizing active strains in samples of soil, metal-containing sites, mining heaps and other biocoenoses, using the dilution method in plates with different media. The critical signs of supposed leaching activity are halo formations around growing colonies in turbid agar media with suspended particles of Ca carbonate or Ca phosphates of low solubility, and in a second group of experiments with insoluble compounds of heavy metals, f. i. oxides. The leaching activity was tested with metal compounds suspended in liquid media and inoculated with active strains of the screening program. First results were reached with oxides of copper (CuO), uranium (U3O8) and an uranium-containing phosphorite.