Bewertung der Verfügbarkeit von nicht extrahierbaren PAK-Rückständen im Boden

Polyzyklische aromatische Kohlenwasserstoffe (PAK) bilden im Boden nicht extrahierbare Rückstände (NER) aus. Ziel dieser Untersuchungen war es, die Verfügbarkeit von 14 C-markierten NER nach Anwendung unterschiedlicher Stressbedingungen zu charakterisieren und somit zu einer Bewertung der Stabilität von NER unter sich verändernden Umweltbedingungen beizutragen. Sowohl biologische als auch physikalische Behandlungen führten zu keiner relevanten Freisetzung von 14 C-Aktivität aus NER. Lediglich die chemische Destabilisierung von organischen Metallkomplexen mit EDTA zeigte einen Effekt auf die Stabilität der NER. Eine Freisetzung von 14 C-Aktivität in extrahierbarer Form fand statt. Entweder handelt es sich dabei um zuvor physikalisch eingeschlossene Moleküle oder um lösliche organische Substanz (DOM)

Metabolites of xenobiotica and mineral oil constituents linked to macromolecular organic matter in polluted environments

The type of association between pollutants and humic substances of soils, sediments and river waters has been investigated. Metabolites, which can arise from the microbiological degradation of polyaromatic hydrocarbons (PAH) and polychlorinated biphenyls (PCB), were cleaved from the macromolecular matrix by selective chemical degradation techniques (OH−, BCl3, Rh/H2). Hydrolysis reactions performed with Na18OH proved that some metabolites of pollutants form stable ester bonds by condensation processes with functional groups of humic substances, a phenomenon which has major implications for transport, toxicity and bioavailability of xenobiotica

Efficient plasmid transformation of the beta-lactam producer Streptomyces clavuligerus

The conditions for optimal formation and regeneration of protoplasts of Streptomyces clavuligerus were established. The optimal temperature for regeneration of protoplasts and for transformation was 26 degrees C in three different regeneration media. The best efficiency of transformation was obtained with 40% polyethylene glycol 1000. The efficiencies of regeneration and transformation increased greatly when protoplasts were obtained from cultures in the early stationary phase of growth. The number of transformants per assay increased linearly with rising concentrations of protoplasts. However, the number of transformants per protoplast decreased at concentrations of protoplasts above 1.5 X 10(9). The total number of transformants rose linearly at increasing plasmid DNA concentrations, but the number of the transformants per microgram of DNA became constant at concentrations above 1 microgram of DNA. Transformation frequencies as high as 5 X 10(5) transformants per microgram of DNA were obtained when plasmid pIJ702 was isolated from S. clavuligerus but not when isolated from Streptomyces lividans.</jats:p