Metabolic Activity Of Sulfate-reducing Bacteria Research Articles

Synergistic effect of microorganisms and a direct current electric field on X70 steel corrosion in a near-neutral solution

In this paper, the corrosion behavior of X70 steel in the near-neutral simulated soil solution (NS4 solution) under the synergistic effect of sulfate reducing bacteria (SRB) and a direct current electric field (DCEF) were explored. The corrosion rate was determined with the electrochemical technique and the corrosion morphology and corrosion products were respectively characterized by SEM and XPS. In the sterile solution, corrosion morphology of X70 steel was pitting and the corrosion rate increased with the increase in DCEF intensity and exposure time. When DCEF was absent, the corrosion rate of X70 steel in bacterial NS4 solution was faster than that in the sterile solution and the corrosion morphology was general corrosion. The acceleration effect of DCEF on corrosion was more significant than that of SRB. Under the synergistic effect of SRB and DCEF, when DCEF intensity increased below 500 V/m, the metabolic activity of SRB was gradually enhanced and the corrosion rate of X70 steel decreased. The protective effect of biofilm weakened the acceleration effect of DCEF on corrosion and the corrosion behavior was controlled by SRB corrosion. When DCEF intensity increased above 1000 V/m, SRB cells were inactivated and the corrosion rate of X70 steel increased. The corrosion behavior of X70 steel was controlled by DCEF. Based on the above research results, preventative actions were proposed.

Autochthonous Micrite to Aphanodolomite: The Microbialites in the Dolomitization Processes

In the present paper, we examine the influence of micrite types, autochthonous or allochthonous, on the dolomitization processes. The recrystallized and dolomitized Carnian samples from Rifugio Vallandro and Alpe di Specie erratic boulders (South Tyrol, Italy) offer a unique example for studying the relationship between microbialites and dolomitization processes. The comparison between the carbonates of the well-preserved erratic boulders of Alpe di Specie and the isochronous, recrystallized, and dolomitized, samples of Rifugio Vallandro, allows for hypothesizing the role of microbialites on dolomitization processes. The Rifugio Vallandro samples represent variously dolomitized boundstone (made of corals, sponges, and peloidal crusts) with a fine texture (aphanodolomite) which contain organic matter relics, suggesting microbial-mediated mineralization. Geomicrobiological characterization of the microbialites from Alpe di Specie indicates that they formed through microbial metabolic activity of sulfate-reducing bacteria, which thrive on organic matter accumulated in the suboxic to anoxic interspaces of the skeletal framework. Similar processes can be hypothesized for the microbialite precursor of Rifugio Vallandro. Extracellular polymeric substance (EPS) and other organic compounds trapped inside the fine crystal matrix can have a role in the dolomitization processes of the microbialites. High pH and high alkalinity, derived from the degradation of organic matter, may be critical in promoting the dolomitization of microbialites because the high pH increases the concentration and activity of the dissolved CO32−, thereby increasing the dolomite supersaturation and reaction rates. This process produces very fine dolomite (aphanodolomite) that replaces the original organic-rich micrite, while the fine crystalline dolomite forming larger euhedral crystals seems to derive from the allochthonous micrite due to the presence of a large amount of siliciclastics and the absence of organic remains.

Metabolic Activity of Sulfate-Reducing Bacteria from Rodents with Colitis.

Sulfate-reducing bacteria (SRB) are anaerobic microorganisms, which use sulfate as an electron acceptor in the process of dissimilatory sulfate reduction. The final metabolic product of these anaerobic microorganisms is hydrogen sulfide, which is known as toxic and can lead to damage to epithelial cells of the large intestine at high concentrations. Different genera of SRB are detected in the large intestine of healthy human and animals, and with diseases like Crohn's disease and ulcerative colitis. SRB isolated from rodents with ulcerative colitis have produced 1.14 (mice) and 1.03 (rats) times more sulfide ions than healthy rodents. The species of Desulfovibrio genus are the most widespread among all SRB in the intestine. The object of our research was to observe and compare the difference of production of sulfide and reduction of sulfate in intestinal SRB isolated from healthy rodents and rodents with ulcerative colitis.

The effect of sulfate-reducing bacteria on hydrogen permeation of X80 steel under cathodic protection potential

The pipelines buried underground are always influenced by sulfate-reducing bacteria (SRB) and cathodic protection (CP). The literature had recorded the fracture accidents of buried pipeline caused by SRB and cathodic potential. To investigate whether SRB can influence the hydrogen damage of pipeline steel under cathodic potential, the synergistic effect of SRB and cathodic potential on hydrogen permeation behavior of X80 steel was investigated by electrochemical tests and optical observation, by which both the growth cycle of microorganism and the applied potential are considered. The results showed that the hydrogen permeation current density of X80 steel in SRB-inoculated solution was three times higher than that without SRB. Serious hydrogen blistering on the surface of specimen was observed in the presence of SRB. The permeation current increases with the negative shifting of the applied cathodic potential in SRB-inoculated solution, which is attributed to the cathodic polarization and the metabolic activities of SRB. The research indicated that the hydrogen damage of pipeline is more likely occurred in the environments with SRB under a more negative cathodic CP potential.

Electrochemical characterization of direct electron uptake in electrical microbially influenced corrosion of iron by the lithoautotrophic SRB Desulfopila corrodens strain IS4

Corrosion of iron infrastructure in anoxic environments is commonly ascribed to the metabolic activity of sulfate-reducing bacteria (SRB), which can influence electrochemical processes on the metallic surface. The present study characterizes electron transfer processes at the electrode/microorganism interface of the specialized lithoautotrophic SRB Desulfopila corrodens strain IS4 that is capable of taking up electrons directly from elemental iron, thereby leading to severe corrosion. Electrochemical analysis of the highly corrosive SRB is performed in bio-electrochemical cells operated with artificial seawater under anoxic conditions, complemented by infrared spectroelectrochemical analysis and environmental SEM observations. In order to provide clear insights into electron transfer processes, sterile controls and a non-corrosive hydrogenotrophic control strain are analyzed in parallel. Remarkably, the electron uptake from electrodes by D. corrodens strain IS4 is not restricted to iron serving as the sole electron donor for the microbial metabolism, but instead proceeds also on graphite and doped germanium cathodes. Consequently, a well-defined electrochemical analysis of the electron uptake mechanism is possible, since corrosion precipitates typically observed on iron electrodes are absent on both of the other cathode materials. Direct electron transfer in the absence of artificial electron mediators is achieved at a potential of −0.4V vs. SHE under neutral conditions. Electrochemical and infrared spectroelectrochemical analysis indicated c-type cytochromes as the redox active components associated with the outer membrane to be involved in the direct electron uptake from reduced surfaces by D. corrodens strain IS4.

REINVESTIGATING CARBONIFEROUS "ACTINOMYCETES": AUTHIGENIC FORMATION OF BIOMIMETIC CARBONATES PROVIDES INSIGHT INTO EARLY DIAGENESIS OF PERMINERALIZED PLANTS

Paleoecological interactions among fossil microorganisms have garnered significant interest within the paleobotanical community; however, an understanding of the early diagenesis of associated plant material is of critical importance when assessing putative body fossils of fungi and bacteria. Structures preserved within permineralized petioles of the Carboniferous fern Botryopteris tridentata Felix (Scott) have been interpreted as the earliest remains of Actinobacteria found in association with vascular plants, but re-examination of the specimens indicates instead that these biomimetic structures (BMS) are authigenic carbonate minerals. Using spinning disk confocal microscopy, we generated monochromatic luminescence maps of BMS found within the phloem cells of Botryopteris. Luminescence was captured at wavelengths of 665 nm, consistent with an interpretation of these structures as disordered dolomites, an inference subsequently corroborated with energy-dispersive X-ray spectrometry (SEM-EDS). The presence of high-magnesium carbonates within Botryopteris is suggestive of an early anaerobic stage of plant tissue degradation characterized by metabolic activities of sulfate-reducing bacteria. Anaerobic biodegradation may also have been performed by chytridiomycetes, and we interpret larger (5–8

English

The successful long-term operation and sustainability of passive systems for the treatment of mining influenced water (MIW) affected by metals and acidity has been challenged by a lack of understanding on organic substrate design. Metabolic activity of sulfate-reducing bacteria (SRB) in bioreactors produces H2S that precipitates dissolved metals, and it is the main mechanism that removes metals from solution. Fermentation products of the organic substrate provided support the SRB indirectly. The relation between changes in bioavailable carbon (C) in the substrate, SO4 2- reduction and metal removal was thus studied. The systems under investigation are two identical 1,500-gallon tanks filled with volume fractions of 0.7 walnut shells, 0.25 corn stover, and 0.05 manure. The tanks have an operating volume of approximately 1,100 gallons, receive influent water at a nominal rate of 1 L/min, and have an estimated hydraulic residence time of about 1.5 days (based on 50% porosity). The bioreactors receive mining influenced water from the National Tunnel in Black Hawk, CO that has a typical metals concentration of 35mg/L Fe, 8mg/L Zn, and 0.6mg/L Cu; pH is circumneutral at 5.5 ±1.0. To assess bioavailable C in the substrate, hot water and acid soluble C and lignin-to- cellulose ratios were periodically analyzed. Preliminary chemical analysis of the substrate suggests that only the hot water extractable fraction (organic acids and labile polysaccharides) changed during the first three quarters of operation. The lignin-to- cellulose ratio during the same period was relatively unchanged, suggesting that the rate of organic substrate depletion was low. Sulfate reduction was variable but sufficient to promote efficient removal of Cu and Zn. After the first 12 months of operation, the average percentages for metal removal in the duplicate bioreactors were >99% for Cu and Zn and 70% for Fe, the latter ranging between 40 and 95%. The low rate of substrate depletion suggests the substrate mixture may provide long-term support of the sulfate-reducing consortium. The bioreactors were able to successfully remove Cu and Zn but Fe removal was problematic. This suggests that extent of SO4 2- reduction was not sufficient to effectively remove iron in the National Tunnel MIW.

Dissimilatory sulfate reduction in hypersaline coastal pans: Activity across a salinity gradient

The impact of salinity on the metabolic activity of sulfate-reducing bacteria in five highly saline to hypersaline coastal pans was studied using a radioactive tracer ( 35 SO 4 2 - ) technique. We recorded sulfate reduction at in situ porewater salinities of up to 422. Furthermore, enumeration of sulfate reduction rates in whole core incubations conducted under in situ conditions suggested a high variability in the activity of sulfate-reducers. Average reduction rates (27–3685 nmol cm −3 d −1) varied according to depth, season and site sampled. The highest reduction rates measured in the hypersaline pan were comparable to the highest reported rates from highly productive salt marsh and microbial mat ecosystems. Correspondingly, the depth-integrated rates (integrated to 12 cm) varied from 6 to 241 mmol m −2 d −1 and were also among the highest ever reported rates. The reduction rates decreased down-core and, surprisingly, were highest in the winter season when the lowest sediment temperatures were encountered. High salt concentrations did not inhibit sulfate reduction rates. Rather, higher rates were measured at pans with higher in situ salinities. In laboratory slurry incubation experiments, sediments from the saltpans were treated with increasing salt concentrations. Regression analysis suggested that the short term response of microbial consortia to up-shock was an increase in sulfate reduction activity up to salinities of 272–311 and 134–244, in hypersaline and highly saline pans, respectively. Beyond these salinities, the cells showed evidence of reduced activities.

Spatial variability of sulfate reduction in a shallow aquifer

The distribution and metabolic activity of sulfate-reducing bacteria (SRB) in a shallow, suboxic aquifer were studied. A radioimaging technique was used to visualize and quantify the activity of sulfate reducers in sediments at a centimetre-level scale. The distribution of SRB metabolic activity was heterogeneous with areas showing little activity far outnumbering areas with high activity. Variation in sulfate-reducing activity was not statistically correlated with variation in depth, bacterial numbers, or the following sediment properties: sediment type (sand, peat or silt), grain size, permeability and hydraulic conductivity. Sulfate-reducing bacteria activity did vary significantly with sediment porosity (multivariate analysis, r = 0.48). We hypothesized that the small pore sizes associated with sediments with low porosity restricted the ability of SRB to grow to high numbers as well as their access to nutrients. To further explore the relationship between pore size and microbial metabolic activity, columns with varying pore diameters were constructed. Sulfate-reducing bacteria in the columns with the smallest pore diameters had the lowest rates of metabolism and SRB metabolic rates increased as the pore diameter increased. For the aquifer studied, sediment porosities and pore sizes were the main factor controlling SRB activity.

Influence of sulfate-reducing bacteria on outdoor hydrogen production by photosynthetic bacterium with seawater.

The application of seawater for bacterial fermentative production is a cost-effective technology. Hydrogen production by marine photosynthetic bacterium with seawater failed to continue after more than 10 days, and was accompanied by the formation of hydrogen sulfide and a change in culture color from red to black. However, substrate consumption in the blackish culture was comparable to that in a hydrogen-producing culture. A decrease in hydrogen production occurred upon the addition of sodium sulfide at concentrations of 1.5 mM or higher. PCR analysis targeted at the 16S rDNA sequence selective for sulfate-reducing bacteria revealed the existence of sulfate-reducing bacteria in inoculation cultures of the phototrophic bacterium and medium for hydrogen production. Hence, the high sulfate concentration of seawater, the low oxidation-reduction potential under hydrogen-producing conditions, and the presence of electron donors such as acetate might promote the metabolic activities of sulfate-reducing bacteria, resulting in the deterioration of hydrogen production with seawater.

Sulfate-reducing bacteria and silica solubility: a possible mechanism for evaporite diagenesis and silica precipitation in banded iron formations

Selective replacement of sulfate-evaporite minerals by silica and the precipitation of silica in association with sulfide mineral phases in banded iron formations may be mediated by the metabolic activities of sulfate-reducing bacteria. Hydrogen sulfide is known to be a product of this metabolism and is often called upon as a source of sulfur for metallic sulfides in sedimentary rocks. We report here on the influence that chemical changes induced by bacterial sulfate reduction have on silica solubility.Controlled in vitro growth experiments with Desulfovibrio desulfuricans and silica show (1) this organism can grow in silica concentrations as great as 400 ppm with no inhibition and (2) growth in the presence of silica yields a decrease in dissolved silica.Growth experiments with 80 ppm silica produced a lowering in dissolved silica from 80 ppm to 60 ppm, a 25% decrease, in just 30 h. Control experiments in the absence of cells resulted in no effective decrease in dissolved silica. The ability of sulfate-reducing bacteria to remove silica from solution may be related to local changes in pH and to hydrogen bonding of amorphous silica followed by polymerization to higher weight molecules.

Stable isotope study of the cyclic diatomite—Claystones from the tripoli formation, Sicily: A prelude to the Messenian salinity crisis

The Tripoli Formation, underlying the Messenian evaporites of Sicily, comprises cyclic alternations of diatomites and claystones that commonly contain dolomite. An oxygen- and carbon-isotope study on the carbonate component of the diatomaceous interbeds records normal marine conditions, whereas the 18O values (+4.0 to +8.5‰) of the dolomite in the claystones signify dolomitization by highly evaporated waters. Extremely negative 13C values (−3.5 to −22.0‰) of this dolomite, certain interbedded limestones, and the overlying Calcare di base denote an organic source of carbon dioxide, the origin of which could be explained by the metabolic activity of sulfate-reducing bacteria in anoxic sediments. This, in turn, implies the former presence of evaporites (?gypsum) before the onset of the Messenian salinity crisis. Eustatic sea-level changes dependent upon the waxing and waning of the Antarctic ice sheet are proposed as the cause of the periodic restrictions in the Tripoli Sea. During high sea-level stands, diatomaceous sedimentation took place under normal marine conditions; during low sea-level stands, restriction and subsequent evaporation of water entering the Tripoli Sea favored the formation of dolomitizing solutions which diagenetically altered the carbonates in the clay-rich sediments. The restriction of the Tripoli Sea during low sea-level stands required the presence of a shallow Atlantic—Mediterranean sill. Progressive tectonic constriction of the connection between the two water bodies, or global eustatic sea-level lowering, is indicated by the extensive dolomitization of the uppermost transitional unit of the Tripoli Formation and the calcitized “evaporite” beds of the Calcare di base. The final phase was total restriction which led to the desiccation of the deep Mediterranean basins and the onset of the Messinian salinity crisis.