Positive and negative aspects of suplhate-reducing bacteria in environment and industry

The submitted work is oriented on the study of two aspects of the sulphate-reducing bacteria metabolism: the metals bioprecipitation and the concrete biodeterioration. The bioprecipitation of metals with the bacterially produced hydrogen sulphide by sulphate-reducing bacteria (SRB) represents the positive effect of the SRB existence in the environment. It allows the industrial exploitation in the area of the removal metals from industrial wastewaters. Referred method involves principal stages such as: hydrogen sulphide bacterial production, metals precipitation by biologically produced hydrogen sulphide, metal sulphides separation, setting pH of the filtrate from previous steps by 1M NaOH and metal hydroxides separation. The basis of the first stage i.e. the hydrogen sulphide bacterial production is the cultivation of SRB. In the laboratory conditions the sodium lactate is the energetic substrate for the growth of bacteria. Its price is not economic for the application in the practice and is needed investigate the alternative substitutes. Therefore was studied the cultivation of sulphate-reducing bacteria to using the selected energetic substrates such as: calcium lactate, glycerol and whey. Experimental studies confirm that all chosen substrates are suitable alternative substrates of sodium lactate for the bacterial sulphate-reduction. In the regard to the efficiency of bacterial sulphate reduction the calcium lactate is the best. The biodeterioration of the concrete presents the negative effect of the SRB existence in the environment. The research was oriented on the simulation of the biodeterioration of concrete samples under the simultaneous influence of the sulphur-oxidising bacteria genera Acidithiobacillus thiooxidans and sulphatereducing bacteria genera Desulfovibrio in the environs of the waste water, the acid mine drainage, the nutrient medium and the distilled water. The observation of the surface structure changes of concrete samples confirms the highest biodeterioration influences in the case of the acid mine drainage application.

New insights of Tripoli and “Calcare di Base” Formations from Caltanissetta (Sicily) and Rossano (Calabria) Basins: a detailed geochemical, sedimentological and bio-cyclostratigraphical study.

<p>A detailed biostratigraphical and cyclostratigraphical study provided the opportunity of cycle-by-cycle correlations between sections from the marginal and deep areas of the Caltanissetta Basin (Sicily), and the northern Calabrian Rossano Basin. All the sections were compared with the Falconara-Gibliscemi composite section. We present new mineralogical and geochemical data on the transition from Tripoli to Calcare di Base (CdB), based on the study of several field sections. The outcrops display good record of the paleoceanographical changes that affected the Mediterranean Sea during the transition from slightly restricted conditions to the onset of the Mediterranean Salinity Crisis (MSC). This approach permitted to better constrain depositional conditions and highlighted a new palaeogeographical pattern characterized by separated sub-basins. The sedimentological and geochemical parameters of these basins introduced a different and diachronous response to the global constraints of the MSC. Our preliminary results display already evidences of paleoenvironmental changes: (1) a lithological transition passing from the Tripoli’s triplet (grey marls, reddish laminites and diatomites) to the complex carbonates of CdB; (2) the appearance of evaporite pseudomorphs implying early stage diagenesis; (3) the presence of sulphur-rich deposits involving process of bacterial sulphate reduction. The local transition from the uppermost part of the Tripoli cycles to the CdB reflects the worsening of the marine connections, leading to the individualisation of semi-closed settings where the marine inputs were not great enough to balance the effects of the climate fluctuations and especially of the evaporation/precipitation budget.</p>

Chemical evidence from laboratory experiments for biokarst development in the Ordos Basin, northwestern China

The present work is designed to simulate the dissolution of sulphate rock under various conditions of different bacterial cell numbers, temperatures and reaction times both in water-rock system and water-rock-bacteria systems by laboratory experiment. The rate of sulphate reduction were estimated using the experimental data. The results suggested that the sulphate-reducing bacteria promote the sulphate rock dissolution and increase the amount of dissolved sulphate. The dissolution of sulphate rock driven by bacterial sulphate reduction results in the formation of sulphate rock karst. The research is an insight into biokarst, which provides a new perspective for the field of petroleum geology.

Origin of fabric-selective dolomitization recognizable in the field: two case studies from Anisian carbonate rocks in the western Balkanides

The origin of dolomitized burrows (Cruziana ichnofacies) in limestones and dolomitic layers in limestone-dolostone ribbon rocks was studied on the basis of petrography, X-ray diffractometry, geochemical data and isotope signatures of the dolomites. Selective dolomitization of the burrows with a local source of Mg occurred in a near-surface setting from non-evaporitic solutions with low Mg/Ca ratio. The low-temperature precipitation of non-stoichiometric (with Ca excess) dolomite was microbially mediated and controlled by bacterial sulphate reduction. The carbon for dolomite formation was largely derived from seawater and/or dissolution of precursor carbonate sediments, and partly derived from the decomposition of organic matter. Selective dolomitization of primarily argillaceous carbonate layers in the ribbon rocks was mainly associated with an autochthonous source of Mg. Clay mineral transformations (i.e., illitization of smectite) at intermediate burial depths supplied Mg ions for the formation of Ca-rich (locally ferroan) dolomite. However, differential diagenesis of the originally clay-rich and clay-poor layers may also have favoured early dolomite precipitation, whereupon contemporaneous seawater was the primary Mg source during shallow burial. The obtained results show that various factors control the formation of fine-grained, non-stoichiometric dolomite with macroscopically recognizable fabric-selective character of replacement.

Sedimentary facies analyses from nano- to millimetre scale exploring past microbial activity in a high-altitude lake (Lake Son Kul, Central Asia)

The fabric of sedimentary rocks in lacustrine archives usually contains long and continuous proxy records of biological, chemical and physical parameters that can be used to study past environmental and climatic variability. Here we propose an innovative approach to sedimentary facies analysis based on a coupled geomicrobiological and sedimentological study using high-resolution microscopic techniques in combination with mineralogical analyses. We test the applicability of this approach on Lake Son Kul, a high alpine lake in central Tien Shan (Kyrgyzstan) by looking at the mineral fabric and microbial communities observed down to the nanoscale. The characterization of microbe–mineral interactions allows the origin of four carbonate minerals (e.g. aragonite, dolomite, Mg-calcite, calcite) to be determined as primary or diagenetic phases in Lake Son Kul. Aragonite was mainly of primary origin and is driven by biological activity in the epilimnion, whereas diagenetic minerals such as Mg-calcite, calcite, dolomite and pyrite were triggered by bacterial sulphate reduction and possibly by methanotrophic archaea. A new morphotype of aragonite (i.e. spherulite-like precursor) occurs in Unit IV (c. 7100–5000 cal. BP) associated with microbial mat structures. The latter enhanced the preservation of viral relics, which have not yet been reported in Holocene lacustrine sediments. This study advocates that microbe–mineral interactions screened down to the nanoscale (e.g. virus-like particles) can be used successfully for a comprehensive description of the fabric of laminated lake sediments. In this sense, they complement traditional facies sedimentology tools and offer valuable new insights into: (1) the study of microbial and viral biosignatures in Quaternary sediments; and (2) palaeoenvironmental reconstructions.