Klaus Bosecker

Technetium reduction and precipitation by sulfate‐reducing bacteria

Resting cells of the sulfate‐reducing bacterium Desulfovibrio desulfuricans ATCC 29577 were able to precipitate the radionuclide technetium, supplied as the pertechnetate anion (TcO4 ‐), under anaerobic conditions by two discrete mechanisms. Sulfidogenic cultures, supplied with sulfate and lactate as an electron acceptor and donor, respectively, precipitated the radionuclide as an insoluble sulfhide. Using electron microscopy in combination with energy‐dispersive x‐ray analysis (EDAX), the precipitate was shown to be extracellular, and contained S as the major element at a fivefold stoichiometric excess to Tc as quantified by proton‐induced x‐ray emission analysis (PIXE). With hydrogen supplied as the electron donor, the pertechnetate anion was utilized as an alternative electron acceptor in the absence of sulfate. The radionuclide was removed from solution, but in these cultures the precipitate was cell associated, with Tc as the major element detected by PIXE (Tc:S ratio of 2:1). Reduction of the radion...

Leaching Heavy Metals from Contaminated Soil by Using Thiobacillus ferrooxidans or Thiobacillus thiooxidans

Iron- and sulfur-oxidizing bacteria identified as Thiobacillus ferrooxidans and T. thiooxidans were successfully enriched from various soil samples contaminated with heavy metals and organic compounds. Depending on the growth medium, the soil sample, and the type of contaminant, the indigenous isolates solubilized > 50% of most of the heavy metals present in the solid sample (As, Cd, Co, Cr, Cu, Ni, V, Zn, B, Be). Leaching with T. ferrooxidans strains resulted in total extraction of Cd, Co, Cu, and Ni. With sulfur-oxidizing bacteria > 80% of Cd, Co, Cu, and Zn was mobilized from rainwater sludge. Pb and Ba were not detected in the leachate, given the insolubility of their sulfate compounds. An increase in pulp density up to 20%, indicating 6.6% total organic carbon in the soil and rubble leach experiment (sample 557), did not inhibit the growth of the indigenous T. ferrooxidans strain. In view of these results, bioleaching appears to have some potential for remediation of heavy metal contaminated soils.

Nocardiopsis metallicus sp. nov., a metal-leaching actinomycete isolated from an alkaline slag dump.

A taxonomic study was carried out on a metal-mobilizing, alkaliphilic bacterium from an alkaline slag dump, strain KBS6(T). The strain produced substrate and aerial mycelia. Growth occurred in the pH range 7.0-10.5, with an optimum at pH 8.5. A salt concentration of up to 10% was tolerated, and various organic substrates were used for growth. The results of a 16S rDNA sequence comparison revealed that strain KBS6(T) belongs to the genus Nocardiopsis. DNA-DNA hybridization with the two closest relatives, Nocardiopsis exhalans and Nocardiopsis prasina, gave similarity values of 18.2 and 44.1%, respectively, which indicated that strain KBS6(T) represents a novel species of the genus Nocardiopsis. This is consistent with the morphological, physiological and chemotaxonomic data. Because of the ability of this micro-organism to solubilize metals, the name Nocardiopsis metallicus sp. nov. is proposed for strain KBS6(T) (= DSM 44598(T) = NRRL B-24159(T)), this being the type strain.

Biodegradation of Crude Oils

Petroleum from well sites in the Gifhorn Trough (Lower Saxony, NW-Germany) and the Maracaibo Basin (Venezuela) contained various types of microorganisms capable of degrading crude oils. Genetically related oils were inoculated with the isolated microorganisms and the degradation of the oils was followed by chromatographic techniques. Parameters important for the reactions (pH, supply of oxygen, nitrogen and phosphorus, reaction medium) were monitored and optimized. The degradation of n-alkanes was followed closely. Microorganisms active in degradation (yeast, bacteria) easily survived a period of inactivity due to missing nutrients and were reactivated within hours to degrade newly added crude oil. Under substrate-limiting conditions selectivity of degradation was found, destroying medium-chain n-alkanes (C20, C21) at a faster rate than long-chain n-alkanes (C30, C31). During degradation the physical parameters of the crude oils (e.g. density, viscosity, average molecular weight) were altered and shifted into the direction of heavy oil. In vitro degraded oil is very similar to oil degraded in nature. Aromatic hydrocarbons and biomarker molecules (steranes and triterpanes) were not degraded under the conditions used. Pyrolysis-GC analysis of asphaltenes revealed no significant changes in the composition of pyrolyzates during biodegradation. There is sufficient evidence that heavy oils - besides some other effects - are generated by the in situ-biodegradation of conventional oils.

Chemical reactions and stability of biomarkers and stable isotope ratios during in vitro biodegradation of petroleum

Abstract Petroleum from the Gifhorn Trough (Lower Saxony, F.R.G.) and the Maracaibo Basin (Venezuela) were analyzed for microorganisms capable of biodegradation. Genetically related oils were inoculated with the isolated microorganisms and the degradation of the oils was followed by chromatographic techniques. Parameters important for the reactions (pH, oxygen concentration, nitrogen, and phosphorus, reaction medium) were monitored and optimized. The degradation of n-alkanes was followed closely. It was shown that the microorganisms responsible for degradation (yeasts and bacteria) could easily survive a period of inactivity due to missing nutrients and could be reactivated within hours to degrade newly added petroleum. Under conditions in which oxygen or nitrogen was limited, selectivity was observed: medium-chain n-alkanes (C18, C20) were degraded faster than long-chain (C30) or short-chain (C14) n-alkanes. Branched-chain alkanes were also degraded. The physical parameters of the oils (e.g. density, viscosity, average molecular weight) were altered as expected during degradation. In vitro degraded oil is very similar to oil degraded in nature. It was found that biomarker molecules are resistant to degradation under the conditions used. Pyrolysis-GC analysis of asphaltenes revealed no significant changes in the composition of pyrolyzates during biodegradation. A small shift in the carbon isotope ratios in the aromatic hydrocarbon fraction was observed between biodegraded and unaltered samples.

Diversity of Iron Oxidizing Bacteria from Various Sulfidic Mine Waste Dumps

More than 100 cultures of acidophilic Fe(II)- and/or sulfur-oxidizing microorganisms from mine waste dumps in 10 different countries all over the world have been maintained in liquid media in the BGR-strain collection for many years. Our 16S rDNA analysis showed that most of the cultivated Fe(II)-oxidizers belong to four genera: Acidithiobacillus, Acidimicrobium, “Ferrimicrobium” and Leptospirillum. All analyzed Acidithiobacillus strains were identified as At. ferrooxidans. The Leptospirillum strains were affiliated with L. ferriphilum or L. ferrooxidans. The Gram-positive strains related to Acidimicrobium or ”Ferrimicrobium” were phylogenetically more diverse than the strains of the genera Acidithiobacillus and Leptospirillum and fell into three separate clusters. While several strains could be identified as syngeneic (16S rDNA) with “Ferrimicrobium acidiphilum”, two other 16S rDNA clusters were distantly related and might represent new species or even new genera. In addition, one new Sulfobacillus strain and one new Alicyclobacillus strain could be identified. Furthermore several strains related to Acidiphilium acidophilum have been detected and form one 16S rDNA cluster.

Bioleaching of silicate manganese ores

Organic acids excreted by microorganisms dissolve manganese from silicate ores. Oxalic acid is more effective than citric, gluconic, and glycolic acid. Eighteen percent of the manganese in manganese silicate ore from Razoare, Romania, was dissolved within 6 days. Improvement of leaching conditions increased this to 20% within 6 h. Besides the manganese in the ore, 45% of the aluminum and 8% of the iron were dissolved in this time interval. This demonstrates that bioleaching of manganese from silicate ore is feasible, thus opening up new possibilities for the mineral processing industry.

Biodegradation of Sulfur Minerals and its Application for Metal Recovery

Abstract Bacteria of the genus Thiobacillus are capable of changing water-insoluble metal sulfides to water-soluble metal sulfates by a set of interacting biochemical and geochemical reactions. These reactions can be utilized for the mobilization of metals from low-grade ores. Biodegradation of sulfide minerals - bacterial leaching - is already being used on a large scale in cases where conditions are appropriate. An enlargement of its possibilities, both with regard to the particular microorganisms used as well as to the ore-type to be leached, is of great economic interest.