Hana Vojtková

Alkaline Technosol contaminated by former mining activity and its culturable autochthonous microbiota

Technosols or technogenic substrates contaminated by potentially toxic elements as a result of iron mining causes not only contamination of the surrounding ecosystem but may also lead to changes of the extent, abundance, structure and activity of soil microbial community. Microbial biomass were significantly inhibited mainly by exceeding limits of potentially toxic metals as arsenic (in the range of 343–511 mg/kg), copper (in the range of 7980–9227 mg/kg), manganese (in the range of 2417–2670 mg/kg), alkaline and strong alkaline pH conditions and minimal contents of organic nutrients. All of the 14 bacterial isolates, belonged to 4 bacterial phyla, Actinobacteria, Firmicutes; β- and γ-Proteobacteria. Thirteen genera and 20 species of microscopic filamentous fungi were recovered. The most frequently found species belonged to genera Aspergillus (A. clavatus, A. niger, A. flavus, A. versicolor, Aspergillus sp.) with the dominating A. niger in all samples, and Penicillium (P. canescens, P. chrysogenum, P. spinulosum, Penicillium sp.). Fungal plant pathogens occurred in all surface samples. These included Bjerkandera adustata, Bionectria ochloleuca with anamorph state Clonostachys pseudochloleuca, Lewia infectoria, Phoma macrostoma and Rhizoctonia sp.

Classification of strain CCM 4446T as Rhodococcus degradans sp. nov.

Strain CCM 4446T, with notable biodegradation capabilities, was investigated in this study in order to elucidate its taxonomic position. Chemotaxonomic analyses of quinones, polar lipids, mycolic acids, polyamines and the diamino acid of the cell-wall peptidoglycan corresponded with characteristics of the genus Rhodococcus. Phylogenetic analysis, based on the 16S rRNA gene sequence, assigned strain CCM 4446T to the genus Rhodococcus and placed it in the Rhodococcus erythropolis 16S rRNA gene clade. Further analysis of catA and gyrB gene sequences, automated ribotyping with EcoRI restriction endonuclease, whole-cell protein profiling, DNA-DNA hybridization and extensive biotyping enabled differentiation of strain CCM 4446T from all phylogenetically closely related species, i.e., Rhodococcus baikonurensis, Rhodococcus qingshengii, Rhodococcus erythropolis and Rhodococcus globerulus. The results obtained show that the strain investigated represents a novel species within the genus Rhodococcus, for which the name Rhodococcus degradans sp. nov., is proposed. The type strain is CCM 4446T ( = LMG 28633T).

Size distributions of nanoparticles from magnetotactic bacteria as signatures of biologically controlled mineralization

Abstract This paper addresses the problem of magnetite nanoparticle size distributions in magnetotactic bacteria. The methods described in the paper can be used to determine the origin of natural magnetite nanoparticle samples. We analyzed 36 histograms related to bacterial, inorganic, and biomimetic nanoparticle sizes. Using statistical software we concluded that the size of the nanoparticles in cultured magnetotactic bacteria follows an extreme value distribution. Magnetite in uncultured samples can be treated as a two-component mixture containing extreme value and/or log-normally distributed nanoparticles. Analysis of the time-dependent formation of bacterial magnetite revealed that the magnetite size distribution transforms from the initial log-normal (young bacterial culture) through normal-like toward the extreme value distribution (evolved culture). It seems that at a certain moment during bacterial magnetite formation, the bacterial system starts to behave as a closed system. The closing of the system must be followed by another unknown process, because restriction of the nutrient supply into magnetosomes is insufficient for the generation of the extreme value distribution. Based on our analysis, approximately 50% of the magnetite particles in the martian meteorite ALH 84001 follow an extreme value distribution

Heterotrophic bacterial leaching of zinc and arsenic from artificial adamite

Artificial adamite [Zn2(AsO4)(OH)] is a convenient structural model because it is isostructural with other rock-forming minerals in secondary ore deposits formed in cementation zones. Microbial activity in these zones accelerates mineral biogeochemical deterioration and metal release, and our results confirmed that Pseudomonas, Rhodococcus and Cupriavidus strains accelerate adamite leaching by 10 to 465 times compared to controls. Here, the Pseudomonas chlororaphis ZK-1 bacterial strain in a static 42-day cultivation proved more effective than Rhodococcus and Cupriavidus by leaching over 90% arsenic and 10% zinc from adamite in one-step in vitro. We evaluated adamite with the VESTA visualization system for electronic and structural analysis, and our results enhance understanding of zinc and arsenic biogeochemical cycles and mobilization, and highlight bacteria’s beneficial natural and biotechnological application in environmental geochemistry and biohydrometallurgy.