Advanced Materials Research Vols. 20-21

Abstract: Open pit mining characterizes the area of Lusatia (Germany), which corresponds to dramatic changes of the natural ecosystem. Landscapes with huge waste heaps and acid mine lakes are created by former mining activities. The studied waste heap is about 70 years old and is situated between two lakes (Restsee 107 and Restsee 108) formed ten years later. Samples taken by drilling drills showed hints of active sulfate reduction activities within the heap and the ground water. Black precipitations were visible on the sediment cores and an intensive H2S odor was noticed. Investigations of the hydrochemistry of the ground water within the heap were started with the drilling of twelve wells along two parallel lines (I, II). Various analytical parameters were measured (see Storch et al. IBS 2007, short lecture topic environmental problems). The bacterial communities of two wells are investigated by molecular methods. The water samples differ in pH (MPL1: 2.4 and MPL11: 4.4) and were therefore chosen to investigate into more detail. Creating a 16S rDNA library, the microbial diversity in the water was characterized. The 200 clones of sample MPL11 were highly diverse: a restriction analysis using the enzyme RsaI revealed 120 different restriction types. Numbers of sequences were related to sulfate reducing bacteria and to uncultivated bacteria from acidic environmental sites. The obtained sequences will be used to study the remaining wells by T-RFLP and to discuss these results in respect to sulfate reduction under acidic conditions.

Abstract: In the Lusatia area a pilot plant for the treatment of acidic mine waters by microbial iron oxidation and a concomitant iron hydroxysulfate precipitation is operated. Molecular based studies of acidic waters from this iron hydroxysulfate producing pilot plant revealed the presence of 16S rRNA gene sequences from undescribed iron-oxidizing bacteria. Most of these were related to autotrophic Betaproteobacteria (see Heinzel et al. IBS 2007, poster number 98). For cultivating different iron-oxidizing bacteria water samples from this pilot plant were directly plated on various solid media. Double-layer plates were used, with a heterotrophic Acidiphiliumstrain in the underlayer, because of the high sensitivity of autotrophic bacteria towards organic substances. The media contained different iron-substrates with and without organic carbon sources. Colonies appeared at the latest after three weeks and they were encrusted with ferric iron. The phylogeny of the isolated strains was determined and the physiological requirements, like temperature, pH optima, preferred carbon source and iron concentrations, were analyzed. Many isolates which were related to Acidithiobacillus ferrooxidans strains could be cultivated, as well as an isolate related to the genus Thiomonas and one isolate related to a Ferribacter polymyxa species. The Thiomonas-like isolate showed best growth in media containing tryptone soya broth, sodium thiosulfate and ferrous sulfate at pH 2.5 and 30°C. The other Betaproteobacterium grew on ferrous sulfate medium at pH 2.5 between 16 and 37°C. In liquid culture experiments the cells of both isolates were attached to the iron minerals built in the medium. These physiological characteristics of the isolates helped to vary parameters in the pilot plant to optimize the process of iron oxidation and improved waste water remediation.

Abstract: The alpha-proteobacterial genus Acidiphilium consists of several acidophilic species, generally known as a part of the mesophilc microbial flora of leaching biotopes. All of them can grow chemoorganotrophically on carbon sources like sugars and many express additional photosynthetic pigments. Thus far, only Ap. acidophilum is known to be capable of chemolithotrophic growth on elemental sulfur oxidation. The oxidation potential of inorganic sulfur species by the other strictly heterotrophic species has not yet been thoroughly investigated. Here, we demonstrate the unequivocal evidence of inorganic sulfur compound oxidation by strains of Ap. cryptum and other Acidiphilium species. Evolutionary and biochemical aspects of this new feature among the heterotrophic Acidiphilium spp. are discussed. This finding will possibly help to solve the long-standing question about the biochemical nature of elemental sulfur oxidation in mesophilic leaching bacteria.

Abstract: The purpose of this work was to characterize elemental sulfur oxidation by a psychrotrophic Acidithiobacillus ferrooxidans culture that originated from an AMD-impacted surface soil in a permafrost area in northern Siberia. In this work, the iron-oxidizing culture was cultivated with elemental sulfur with and without Fe2+ or Fe3+ in flasks on a shaker to avoid oxygen limitation.