Abstract: Colonies of iron-oxidising acidophilic bacteria were isolated on solid media containing up to 500 mM NaCl from non-saline samples from the Rio Tinto (Spain). One of these isolates was identified as an "Acidithiobacillus ferriphilus" strain. Laboratory cultures of the type strain of Acidithiobacillus ferridurans grown on hydrogen for one year were also found to adapt to the presence of 500 mM salt. This culture also grew on sulfur, but not on ferrous iron, in media containing 500 mM NaCl. It regained its ability to oxidise iron only after protracted incubation in salt-free media. Molecular analysis found an insertion of about 1.5 kb in the regulatory region of the rus operon of the strain that was unable to oxidize iron. This insertion was lost in the strain that had subsequently regained this ability. Our results suggest that chloride tolerance and dissimilatory oxidation of iron by these bacteria do appear to be mutually exclusive.
Abstract: Cueva de la Mora and Guadiana are two acidic mine pit lake in the Iberian Pyrite Belt (south-west Spain) that exhibit depth-related stratification, which is in turn reflected in the bacterial community population the different layers. Here we describe the microbial communities present in samples of sediments located close to the surface and deep within the lakes, which show interesting contrasts to planktonic communities.
Abstract: Acidithiobacillus ferrooxidans and Acidithiobacillus ferrivorans are used in bioleaching to recover metals such as copper or gold from low-grade ores. At. ferrooxidans is one of the best studied bioleaching microorganisms. At. ferrivorans is known for its ability to leach ores at low temperature. Both microorganisms are involved in acid mine drainage (AMD) formation. The cells are embedded in extracellular polymeric substances (EPS), which play an important role in the attachment to metal-sulfide-surfaces and in catalysis of their dissolution. EPS amounts and compositions differ, depending on the energy source, as it was shown for At. ferrooxidans R1. Recently, At. ferrooxidans strains were reclassified into four different subgroups, which are considered to correspond to four different species. As well, a biofilm study, using three of these closely related iron-oxidizing Acidithiobacillus species, demonstrated differences regarding attachment to pyrite among them. Consequently, this study focuses on the investigation of At. ferrooxidans and At. ferrivorans species and their EPS composition with regard to varying cultivation conditions. Also different energy sources like, elemental sulfur or pyrite were tested. EPS were extracted by the use of a cation exchange resin (DOWEX). Obtained EPS were analyzed for their total amount of proteins, extracellular DNA (eDNA) and carbohydrates.
Abstract: Although acidophilic iron oxidizing bacteria related to “Ferrovum myxofaciens” P3G have been detected in various mining sites the knowledge about their physiology is limited to the type strain “F. myxofaciens” P3G. In order to further the knowledge on the metabolic capacity of “Ferrovum” related iron oxidizers we conducted a comparative genome analysis of three “Ferrovum” strains: JA12, PN-J185 and Z-31 (Z-31). The results of the phylogenetic analysis and the genome-to-genome distance calculation indicate that Z-31 belongs to a different “Ferrovum” species than JA12 and PN-J185. Comparative genome analyses revealed variations regarding the carbon, nitrogen and energy metabolism of the three strains which also corroborate the results concerning their phylogenetic relationship.
Abstract: The methods of biodegradation are of special interest because they help solving environmental problems of wastes detoxification from gold-mining operations. The use of bacterial strains is a promising approach in the field of biotechnology to destruct cyanide-bearing compounds. The diversity of microbial communities both in heap in situ and in the enriched cultures was studied with molecular genetic methods. The differences in representation of bacteria, cultivated in unexploitable and operating heaps, are territory, site and heap specific. The strains of Pseudomonas sp. and Methylobacterium sp. possess the biotechnological potential and might be used in biodegradation of heap leaching wastes in extreme continental climate.
Abstract: Leptospirillum ferriphilum is an acidophilic iron-oxidizing bacterium that is relevant for chemical leaching of sulfide ores. In the extremely acidic conditions found in bioleaching operations, this microorganism deals with an abundant supply of soluble iron and other metals that might induce oxidative damage to biomolecules through the generation of reactive oxygen species (ROS). We evaluated the role of Dyp-type peroxidase in the protection against oxidative stress in L. ferriphilum DSM14647. The genetic region encoding dypA was cloned and sequenced. The predicted DypA enzyme is 295 amino acids long with an estimated molecular mass of 32.9 kDa containing a highly conserved peroxide reduction motif. Genetic complementation of catalases/peroxidases-deficient Escherichia coli cells indicated that expression of dypA from L. ferriphilum restored the resistance to hydrogen proxide to levels exhibited by the wild type strain. Exposure of L. ferriphilum to hydrogen peroxide leads to a significant transcriptional activation of dypA suggesting its involvement in the response to oxidative stress in this bacterium. This is the first Dyp-type peroxidase characterized from an acidophilic microorganism, making it a potential candidate for research in basic and applied biology.
Abstract: During the 20th century, Germany belonged to the world’s largest producers of lignite coal. Approaches for remediation of lignite spoil and overburden material were carried out since at least the last 50 years. Today, results of former remediation can be evaluated by their long-term effects. Coal spoil seepage waters can impact billions of m3 of ground water in involved areas for a very long time horizon (eternity impacts).
In the last years our working group had studied especially lignite coal spoil sites in the Lusatia (East Germany) with sandy substrates and faster vertical mass transport processes. In new investigations, another coal spoil site in Middle Germany with more cohesive soil substrates and layers of drift clays was studied, and geochemical and microbial parameters were characterized. The investigated site partially had a remediated topsoil layer since 40 years, and since this time agricultural cultivation of different plants (grains, legumes, Pocaceae) was performed. In this paper, data of different microbial populations in the coal spoil substrate and geochemical background data are given, and they are compared with former data of microbial communities in sandy substrates and their impact to the environment. Finally, the success of long-term remediation of such sites, the influence onto microbial life and impact to the environments will be compared and discussed.
Abstract: Strains of acidophilic bacteria, isolated from different global locations, were shown to be representatives of a novel genus within the Firmicutes phylum. All isolates oxidised and reduced iron and catalysed the oxidative dissolution of pyrite. Together they formed two distinct phylogenetic clusters, one of which included mesophilic strains that did not oxidise sulfur, and the other thermotolerant/moderately thermophilic strains that could oxidise sulfur. The novel genus Acidibacillus is proposed for these new isolates, to include A. ferrooxidans (mesophilic iron-oxidising strains) and A. sulfooxidans (moderately thermophilic iron-and sulfur-oxidising strains) as candidate species.