Competition for oxygen by iron and 2,4,6-trichlorophenol oxidizing bacteria in boreal groundwater

Kinetics of simultaneous iron and 2,4,6-trichlorophenol (TCP) oxidation by groundwater enriched cultures were studied in order to reveal the competition for oxygen in aerobic in situ bioremediation of boreal groundwater. Chemical iron oxidation at near neutral pH in synthetic groundwater depended by the first order on the concentrations of ferrous iron and dissolved oxygen and by the second order on pH. The chemical iron oxidation rate constant was on average 2.2 x 10(13)mol(-2)L(2)atm(-1)min(-1). Chemical iron oxidation was insignificantly affected by natural organic matter, 2,4,6-tri-, 2,3,4,6-tetra- or pentachlorophenol in groundwater. Biological oxidation of iron followed zero-order kinetics. At pH of 6.3 and dissolved oxygen (DO) concentration of 11.5 mgL(-1), the rate of biological iron oxidation was 3.8 x 10(-4)mmolL(-1)min(-1) and up to one order of magnitude higher than the chemical oxidation rate, 5.2 x 10(-6) mmolL(-1)min(-1). Biological oxidation of iron was completely inhibited by pentachlorophenol at 23 micro mol-1. With a groundwater enriched culture, oxygen was consumed at higher rates by 2,4,6-TCP oxidizers (2.5-7.6 x 10(-5)mmolDOL(-1)min(-1)) than the iron oxidizing bacteria (0.8-3.1 x 10(-5) mmolDOL(-1)min(-1)) at both low and saturated DO-concentrations. The results indicate that in situ iron oxidation is predominantly biogenic in the studied boreal aquifer. 2,4,6-TCP degrading bacteria consumed DO at higher rates than the iron oxidizing bacteria and thereby, favour bioremediation of the polychlorophenol contaminated groundwater.     

Direction of glucose fermentation towards hydrogen or ethanol production through on-line pH control

The present study investigated the production of hydrogen (H₂) and ethanol from glucose in an Anaerobic Continuous Stirred Tank Reactor (ACSTR). Effects of hydraulic retention time (HRT) and pH on the preference of producing H₂ and/or ethanol and other soluble metabolic products in an open anaerobic enriched culture were studied. Production rates of H₂ and ethanol increased with the increase of biomass concentration. Open anaerobic fermentation was directed and managed through on-line pH control for the production of H₂ or ethanol. Hydrogen was produced by ethanol and acetate-butyrate type fermentations. pH has strong effect on the H₂ or ethanol production by changing fermentation pathways. ACSTR produced mainly ethanol at over pH 5.5 whereas highest H₂ production was obtained at pH 5.0. pH 4.9 favored the lactate production and accumulation of lactate inhibited the biomass concentration in the reactor and the production of H₂ and ethanol. The microbial community structure quickly responded to pH changes and the Clostridia dominated in ACSTR during the study. H₂ production was maintained mainly by Clostridium butyricum whereas in the presence of Bacillus coagulans glucose oxidation was directed to lactate production.     

Bioelectricity production on xylose with a compost enrichment culture

An exoelectrogenic culture was enriched on 1.0 g/L xylose from a compost sample in two-chamber microbial fuel cells (MFCs). Electricity production was optimized by changing mixing type, external resistance, xylose concentration and pH. Furthermore, the changes in microbial communities after each optimization step were monitored with PCR-DGGE. Electricity production was highly dependent on operational conditions that affected power densities (PD), Coulombic efficiencies (CE), substrate degradation, utilization of soluble metabolites for electricity production and stability of MFC performance. The optimum operational conditions for electricity production were without mixing, 100 Ω external resistance, 0.5 g/L xylose and pH 7. With optimized operational conditions PD of 590 mW/m² and CE of 82% were obtained. Microbial community composition, consisting mainly of Geobacter sulfurreducens, Escherichia coli, Sphaerochaeta sp. TQ1 and Bacteroides species, was mainly affected by MFC configuration, i.e. electrical connections, which likely affected the anode potential.     

Natural organic matter (NOM) removal and structural changes in the bacterial community during artificial groundwater recharge with humic lake water

This study evaluated the removal of natural organic matter (NOM) and structural changes in the microbial community during infiltration of humic lake water at three artificial groundwater recharge (AGR) sites in Finland. The three sites were at waterworks in H?meenlinna, Jyv?skyl? and Tuusula, sites A, B and C, respectively. Site A used groundwater recharge by both basin and sprinkling infiltration, site B used only sprinkling infiltration, and site C used only basin infiltration. Reductions of total organic carbon at sites A, B and C were 91%, 84% and 74%, respectively, in the winter, and 88%, 77% and 73%, respectively, in the summer. The Finnish national recommended value of 2 mg/l for TOC was achieved at all sites and the TOC of natural groundwater at site C was much lower, at 0.6 mg/l. Large molecular fractions of NOM were removed more efficiently than the smaller ones. Total amount of DAPI-stained cells decreased during infiltration at sites A, B and C in winter by 94%, 94% and 75% and in summer by 96%, 97% and 94%, respectively. Bacterial communities in raw waters and extracted groundwaters were diverse with changes occurring during infiltration, which was shown by DNA extraction followed by PCR of 16S rRNA genes and denaturing gradient gel electrophoresis (DGGE) fingerprinting. While the natural groundwater microbial community was diverse, it was different from that of the extracted groundwater in the AGR area. Simultaneous organic carbon removal and the decrease of bacterial counts during infiltration indicated biodegradation. In addition, the changing DGGE profiles during the process of infiltration, demonstrated that changing environmental conditions were reflected by changes in bacterial community composition.     

Spatial and temporal changes in Actinobacterial dominance in experimental artificial groundwater recharge

Artificial groundwater recharge (AGR) is used in the drinking water industry to supplement groundwater resources and to minimise the use of chemicals in water treatment. This study analysed the spatial and temporal changes of microbial communities in AGR using two test systems: a nutrient-amended fluidized-bed reactor (FBR) and a sand column. Structural changes in the feed lake water (Lake Roine), FBR, and sand column bacterial communities were determined by denaturing gradient gel electrophoresis (DGGE) and the length heterogeneity analysis of amplified 16S rRNA genes (LH-PCR). Two clone libraries were created to link the LH-PCR results to the dominant bacterial groups. The lake water bacterial community was relatively stable, with three bands dominating in all LH-PCR products. The most dominant fragment accounted for up to 72% and was derived from Actinobacteria. Based on the clone libraries and LH-PCR data, Actinobacteria also dominated in the unattached bacterial community of the FBR, whereas several Proteobacterial groups were more abundant on the FBR carrier particles. In the stabilised AGR system a major change in the community structure of the lake water bacteria took place during passage within the first 0.6 m in the sand column as the community composition shifted from Actinobacteria-dominated populations to a diverse, mainly Proteobacterial communities. Concurrently, most of the dissolved organic carbon (DOC) was removed at this stage. In summary, the study showed that the make-up of microbial communities in experimental AGR systems responded to changes in their environment. LH-PCR showed potential as a method to determine microbial community dynamics in long-term studies at real-scale AGR sites. This is the first step to provide data on microbial community dynamics in AGR for drinking water production.     

Chloride‐promoted leaching of chalcopyrite concentrate by biologically‐produced ferric sulfate

The effects of chloride ions on chalcopyrite leaching by biologically‐produced ferric sulfate solution and on the iron‐oxidizing culture were determined. Chloride ions significantly increased chalcopyrite leaching by ferric sulfate at 67 °C and 87 °C, but slowed down the leaching at 50 °C. At 90 °C, chloride at 5 g dm^?3 (0.25 g Cl^? g^?1 concentrate) increased the copper yield from 60 to 100% in approximately 2 weeks. Further increase in Cl^? concentration did not affect the leaching. Addition of chloride increased both leaching yields and iron precipitation, which shows that the passivation was not due to iron precipitation. A decreased Ag‐potential of 60 mV against an Ag/AgCl reference electrode in the presence of Cl^? indicates the accumulation of partially oxidized forms of dissolved sulfur compounds such as thiosulfate and polythionate instead of elemental sulfur and, thus, a decrease in sulfur passivation. A chloride concentration of 5 g dm^?3 did not affect the iron oxidation rate of the iron‐oxidizing culture dominated by Leptospirillum ferriphilum. Copyright © 2004 Society of Chemical Industry     

Bioleaching of acid‐consuming low‐grade nickel ore with elemental sulfur addition and subsequent acid generation

The bioleaching of a nickel concentrate and an acid‐consuming nickel ore was studied using a co‐culture of Acidithiobacillus ferrooxidans and A. thiooxidans, as well as a thermophilic enrichment culture, VS2. The VS2 was dominated by a Sulfolobus species related to Sulfolobus metallicus. Nickel concentrate was readily solubilized with A. ferrooxidans and the VS2, resulting in nickel yields of 56% and 100%, respectively. Low‐grade nickel ore required 350 g H₂SO₄ kg^?1 ore for maintaining the pH of the leaching solution below 3. To overcome the high acid demand, biological elemental sulfur oxidation was combined with the ore leaching. Leaching of a 2% (wt/vol) nickel ore with a co‐culture of A. thiooxidans and A. ferrooxidans resulted in nickel yield of up to 86% with acid supplementation of 290 g H₂SO₄ kg^?1 ore. When coupled with biological sulfur oxidation, an 86% nickel recovery was achieved with 0.5% (wt/vol) ore concentration without further sulfuric acid addition. The VS2 oxidized sulfur at a rate of 0.063 g L^?1 d^?1 and the simultaneous nickel ore leaching resulted in 100% nickel yield. In summary, the potential of using elemental sulfur addition and subsequent biological acid generation to maintain the low pH during bioleaching of an acid‐consuming nickel ore was demonstrated. Copyright © 2005 Society of Chemical Industry     

Plasma miR-9-3p and miR-136-3p as Potential Novel Diagnostic Biomarkers for Experimental and Human Mild Traumatic Brain Injury

Noninvasive, affordable circulating biomarkers for difficult-to-diagnose mild traumatic brain injury (mTBI) are an unmet medical need. Although blood microRNA (miRNA) levels are reportedly altered after traumatic brain injury (TBI), their diagnostic potential for mTBI remains inconclusive. We hypothesized that acutely altered plasma miRNAs could serve as diagnostic biomarkers both in the lateral fluid percussion injury (FPI) model and clinical mTBI. We performed plasma small RNA-sequencing from adult male Sprague–Dawley rats (n = 31) at 2 days post-TBI, followed by polymerase chain reaction (PCR)-based validation of selected candidates. miR-9a-3p, miR-136-3p, and miR-434-3p were identified as the most promising candidates at 2 days after lateral FPI. Digital droplet PCR (ddPCR) revealed 4.2-, 2.8-, and 4.6-fold elevations in miR-9a-3p, miR-136-3p, and miR-434-3p levels (p < 0.01 for all), respectively, distinguishing rats with mTBI from naïve rats with 100% sensitivity and specificity. DdPCR further identified a subpopulation of mTBI patients with plasma miR-9-3p (n = 7/15) and miR-136-3p (n = 5/15) levels higher than one standard deviation above the control mean at <2 days postinjury. In sTBI patients, plasma miR-9-3p levels were 6.5- and 9.2-fold in comparison to the mTBI and control groups, respectively. Thus, plasma miR-9-3p and miR-136-3p were identified as promising biomarker candidates for mTBI requiring further evaluation in a larger patient population.     

Molecular diagnosis of human rhinovirus infections: comparison with virus isolation

To compare the sensitivity and specificity of RT-PCR with that of virus isolation in the detection of human rhinoviruses, we tested nasopharyngeal aspirates from 200 patients on the 1st and 7th days after the onset of the common cold. An assay utilizing a short amplicon in the conserved 5' noncoding region was found highly sensitive. Of 192 positive samples altogether, 65 were found positive by RT-PCR only, 6 were positive by isolation exclusively, and 121 gave positive results in both tests.     

Ultrasound evaluation of mechanical injury of bovine knee articular cartilage under arthroscopic control

A local cartilage injury can trigger development of posttraumatic osteoarthritis (OA). Surgical methods have been developed for repairing cartilage injuries. Objective and sensitive methods are needed for planning an optimal surgery as well as for monitoring the surgical outcome. In this laboratory study, the feasibility of an arthroscopic ultrasound technique for diagnosing cartilage injuries was investigated. In bovine knees (n = 7) articular cartilage in the central patella and femoral sulcus was mechanically degraded with a steel brush modified for use under arthroscopic control. Subsequently, mechanically degraded and intact adjacent tissue was imaged with a high frequency (40 MHz) intravascular ultrasound device operated under arthroscopic guidance. After opening the knee joint, mechanical indentation measurements were also conducted with an arthroscopic device at each predefined anatomical site. Finally, cylindrical osteochondral samples were extracted from the measurement sites and prepared for histological analysis. Quantitative parameters, i.e., reflection coefficient (R), integrated reflection coefficient (IRC), apparent integrated backscattering (AIB), and ultrasound roughness index (URI) were calculated from the ultrasound signals. The reproducibilities (sCV %) of the measurements of ultrasound parameters were variable (3.7% to 26.1%). Reflection and roughness parameters were significantly different between mechanically degraded and adjacent intact tissue (p < 0.05). Surface fibrillation of mechanically degraded tissue could be visualized in ultrasound images. Furthermore, R and IRC correlated significantly with the indentation stiffness. The present results are encouraging; however, further technical development of the arthroscopic ultrasound technique is needed for evaluation of the integrity of human articular cartilage in vivo.