Papers by Author: Christian Thyssen

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Authors: Francisco Issotta, Paulo C. Covarrubias, Ana Moya-Beltrán, Sören Bellenberg, Christian Thyssen, Wolfgang Sand, Harold Nuñez, Cristóbal Mena, David S. Holmes, Raquel Quatrini, Mario Vera Véliz
Abstract: The family Acidiferrobacteraceae (order Acidiferrobacterales) currently contains three genera of chemolithoautotrophs: Sulfuricaulis (2016), Sulfurifustis (2015) and Acidiferrobacter (2011). While the two former are neutrophilic sulfur oxidizers isolated from lake sediments in Japan, the latter is an extremely acidophilic, moderately osmophilic, thermotolerant iron/sulfur oxidizer known to occur in macroscopic streamers in Rio Tinto, Spain and in acid waters worldwide. The type strains of both Sulfuricaulis limnicola (HA5T) and Sulfurifustis variabilis (skN76T) have been sequenced, and the draft genome of the ZJ isolate of Acidiferrobacter thiooxydans (MDCF01) has recently been deposited in public databases. Despite this fact, little evidence on the genomic diversity and evolution of this group has been presented so far. Using comparative genomic analyses and phylogenetic reconstruction strategies, we explored the evolutionary information contained in the available genome sequences to shed light on the taxonomic status of a novel isolate of the genus Acidiferrobacter (SP-III/3; DSM 27195).
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Authors: Christian Thyssen, David Holuscha, Jens Kuhn, Friederike Walter, Wolfram Fürbeth, Wolfgang Sand
Abstract: Bioleaching and biocorrosion are based on similar biochemical processes. Microbe-surface interaction, biofilm formation and concomitant extracellular polymeric substance (EPS) production gained increasing interest in the past decades. Nowadays it is generally accepted that biofilm formation and an accompanying formation of manganese oxides by manganese oxidizing bacteria such as Leptothrix spp. account for one type of pitting corrosion of stainless steel (SS). However, little is known about biofilm formation, EPS composition of manganese oxidizing microorganisms and their influence on microbiologically influenced corrosion. Consequently, we studied biofilm formation of Leptothrix discophora, the biooxidation of manganese in biofilms on floating filters as well as biofilm formation on stainless steel and the involved corrosion processes. Cells were visualized by epifluorescence (EFM) or confocal laser scanning –microscopy (CLSM). Additionally, the influence of biofilm formation and biooxidation of manganese by L. discophora on the open circuit potential (OCP) and pitting potential (Epit) of stainless steel was measured using a 3 electrode setup. L. discophora grew well in biofilms on floating filters and on SS coupons and incorporated in both conditions Mn2+ in the form of MnO2 from the bulk phase into the biofilm. OCP measurements of actively manganese-oxidizing biofilms on stainless steel showed a significant ennoblement of ≥200 mV.
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Authors: Claudia Janosch, Christian Thyssen, Mario A. Vera, Violaine Bonnefoy, Thore Rohwerder, Wolfgang Sand
Abstract: The elemental sulfur oxidising enzyme Sulfur Oxygenase Reductase (SOR) is very well investigated in acidothermophilic archaea, such as Acidianus brierleyi and Sulfolobus metallicus. In contrast, not much is known about the biochemistry of elemental sulfur oxidation in acidophilic bacteria. Recently, however, the SOR-encoding gene has been found also in a bacterial strain closely related to the moderate thermophile Acidithiobacillus caldus. Confusingly, for the latter species, also the involvement of the SOX system as well as thiosulfate:quinone oxidoreductase (TQO) and tetrathionate hydrolase (TTH) in sulfur compound oxidation has been proposed based on genome analysis. In this study, we have detected the sor-gene in other Acidithiobacillus caldus-like strains, isolated from various bioleaching habitats, indicating that SOR plays an important role in sulfur oxidation in this species. Based on sequence comparison, the new bacterial sor-genes are closely related and distant from the known archaeal sequences as well as from the SOR found in the neutrophilic bacterium Aquifex aeolicus. In addition, SOR activity has been detected in crude cell extracts from all Acidithiobacillus caldus-like strains tested. The enzyme is truly thermophilic as highest activities were achieved at 65 °C, which is far beyond the growth optimum of Acidithiobacillus caldus. This finding may give rise to the question whether the presence of SOR in Acidithiobacillus caldus is only relevant while growing at elevated temperatures. Currently, experiments are performed for testing this hypothesis (comparing growth and enzyme activities at 30 vs. 45 °C).
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