Basic Aspects of Electrode Potential Change in Submerged Fermentation

The platinum electrode potentials relative to the standard half cell depended on a pH value, dissolved oxygen concentration, equilibrium constant and oxidation reduction potentials of the liquid The overall potential change in submerged fermentation gave no independent information on these individual factors A thermostatic and pH-static apparatus excluded influences of temperatures and pH values on the electrode pontentials If the determination was completed for short time duration, potentials were governed by the dissolved oxygen tension. While the oxygen concentration was maintained at a same level, redox potential changes became a dominant. This measurement of redox potential, which gave the concentration of extremely low dissolved oxygen that could not be detected by the membrane-coated oxygen electrode, was practically useful for the control of aerobic fermentation     

The microbial environment of marine deposit-feeder guts characterized via microelectrodes

Microbial viability and growth in animal guts are dependent upon conditions influenced by both the physiological activities of the animal and the activities of the microbes themselves. To examine the relative contribution of these influences, the guts of Molpadia intermedia (a subtidal holothuroid) and a variety of other marine deposit feeders from diverse habitats were probed with mini- or microelectrodes to measure oxygen, Eh, and pH. In general, bulk oxygen and pH conditions of the gut mimicked those of ambient sediments, revealing nearly neutral pH and zero oxygen in sub- and intertidal animals, with more oxygen in bathyal animals ingesting oxygenated sediments. Eh in guts of subsurface deposit feeders that likely subduct and aerate sediments before ingestion did not mimic sediments. Axial Eh profiles, in contrast to those of pH and oxygen, revealed significant changes along the gut. In most deposit feeders, values decreased from mouth to midgut, suggesting high rates of microbial metabolism within the gut. Increases in Eh were observed in the most distal portion of guts, however, likely due to anal intake of aerated water, and throughout the guts of terebellid polychaetes that feed on highly reducing sediments. This addition of a strong oxidant by the animal may be necessary to avoid sulfide poisoning and may provide access to organic products by stimulating chemoautotrophy. Radial profiles of the gut revealed sharp gradients of Eh and oxygen. In general, steep redox gradients stimulate bacterial metabolism and may lead to exceptionally high respiratory rates. Radial diffusion calculations made using oxygen profiles surrounding the gut reveal that, as predicted by digestion theory, oxygen consumption rates are rapid and are higher in the hindgut, where the digestive products of the animal are available to microbes, than in the foregut.Offprint requests to: C. Plante.     

Factors influencing the extent and development of the oxic zone in sediments

Dissolved oxygen concentrations in river-sediment porewaters are reported and modelled using a zero-order reaction rate and the Monod equation. After mixing the sediments and allowing settling, the dissolved oxygen profile in the bed-sediment was expected to reach a steady-state rapidly (< 1 h). However changes in the vertical profile of oxygen over a period of 38 days revealed that the penetration of oxygen increased and the dissolved oxygen flux at the interface decreased with time, probably as the oxidation kinetics of organic matter and redox reactions in the sediment changed. Experiments with three contrasting silt and sand dominated sediments (organic matter content between 0.9 and 18%) at two water velocities (ca 10 and 20 cm s^–1) showed that the dissolved oxygen profiles were independent of velocity for each of the sediments. The most important controls on the reaction rate were the organic matter content and specific surface area of the sediment. A viscous diffuse-boundary-layer above the sediment was only detected in the experiments with the silt sediment where the sediment oxygen demand was relatively high. In the coarser sediments, the absence of a diffuse layer indicated that slow oxidation processes in the sediment controlled the dissolved oxygen flux at the interface. The problem of determining a surface reference in coarse sediment is highlighted. The results are discussed with reference to other studies including those concerned with estuarine and marine sediments.     

Sediment Chemistry of Lake Bhim Tal,U. P., India

Certain chemical constituents (NO₃-N, bio-available P, Ca, Na, K, Mn, Cu, Co and organic matter) together with pH, Eh and clay content of surface sediments at various depths of the overlying water in Lake Bhim Tal were examined during 1977—1978. In addition, NH₃-N and dissolved oxygen at the mud-water interface (water immediately above the sediments) were measured. The values of Eh, pH and NO₃-N in the sediments showed a negative relationship with water depth and positive relationship with dissolved oxygen at the interface. The other variables of the sediment were positively related to water depth and negatively related to dissolved oxygen at the interface. Organic matter, K, Na and Ca showed positive relationship with the amount of clay while the cations (K, Na, Ca) and trace metals (Cu, Mn, Co) showed a positive relationship with the amount of organic matter in the sediments.     

Dark Carbon Fixation: An Important Process in Lake Sediments

Close to redox boundaries, dark carbon fixation by chemoautotrophic bacteria may be a large contributor to overall carbon fixation. Still, little is known about the relative importance of this process in lake systems, in spite the potentially high chemoautotrophic potential of lake sediments. We compared rates of dark carbon fixation, bacterial production and oxygen consumption in sediments from four Swedish boreal and seven tropical Brazilian lakes. Rates were highly variable and dark carbon fixation amounted up to 80% of the total heterotrophic bacterial production. The results indicate that non-photosynthetic carbon fixation can represent a substantial contribution to bacterial biomass production, especially in sediments with low organic matter content.     

Importance of biological and abiotic factors for geochemical cycling in a freshwater eutrophic lake

Here we report the results of a comprehensive biogeochemical monitoring of Rostherne Mere in 1998, including changes in dissolved oxygen, organic carbon and nitrogen, nitrate/nitrite, ammonia, Al, Na, S, K, Mg, Ca, Si, Fe, Mn, orthophosphate, particulate N & P, suspended solids, temperature, pH, chlorophyll-a and zooplankton. The results demonstrated the major influence of primary producers on the overall geochemical cycling of N, P and Si, and suggested that the significance of zooplankton might have been previously underestimated. For major anions and cations, however, the influence of biota on lake water concentrations appeared to be negligible, reflecting the fact that these chemicals were present far in excess of plankton requirements. Thus changes in concentrations of Ca, K, Na, Mg and S were rather limited and must have reflected changes in hydrological and meteorological parameters. K, however, demonstrated a transitional pattern, reflecting some influence of biological uptake. During the stratification period, the slow processes of bacterial decomposition in the hypolimnion gradually released chemicals contained in the materials accumulated in the bottom layer, remarkably increasing the concentrations of dissolved compounds of those elements present in amounts comparable with the pool stored in the sedimenting detritus (e.g. orthophosphate P, ammonia N, Si and DOC). The decomposition also resulted in a drop in the redox potential, followed by partial denitrification and chemical release from the sediments. The hypolimnion of the Mere was confirmed to remain at the stage of Mn release, characterised by accumulation of DOC, orthophosphates, ammonia and initial stages of denitrification. High levels of P released from the sediments during the stratification period suggest that the lake’s recovery after sewage diversion might be further delayed.     

The influence of light and nutrient addition upon the sediment chemistry of iron in an arctic lake

The geochemical response of sediments to increased nutrient input to an Alaskan, arctic lake was examined using direct measurements of sediment-water chemical fluxes. An unexpected increase in Fe flux occurred when sediments were exposed to high incident radiation and nutrient concentrations. Correlation between light and acid-soluble Fe concentrations suggests that photoreduction of Fe(III) oxides may occur, but nutrient addition enhanced the effect indicating that primary productivity was also important. The processes controlling the flux of Fe from sediments in this lake were complex and included the redox potential (dissolved oxygen concentration) of the water, quality of organic matter present in the sediment, light, and nutrients supplied from the sediments and/or water column. These four factors together with the possibility of direct uptake of Fe by phytoplankton and the possible release of algal reductants may contribute to Fe cycling in this lake.     

Nutrient biogeochemistry in the water column (N,P, Si) and porewater (N) of sandy sediment of the Scheldt estuary (SW-Netherlands)

The Scheldt river drains a densely populated and industrialized area in northern France, western Belgium and the south-west Netherlands. Mineralization of the high organic load carried by the river leads to oxygen depletion in the water column and high concentrations of dissolved nitrogen and phosphorus compounds. Upon estuarine mixing, dissolved oxygen concentrations are gradually restored due to reaeration and dilution with sea water. The longitudinal redox gradient present in the Scheldt estuary strongly affects the geochemistry of nutrients. Dissolved nutrients in the water column and dissolved nitrogen species in sediment porewaters were determined for a typical summer and winter situation. Water column concentration-salinity plots showed conservative behaviour of dissolved Si during winter. During summer (and spring) dissolved Si may be completely removed from solution due to uptake by diatoms. The geochemistry of phosphorus was governed by inorganic and biological processes. The behaviour of nitrogen was controlled by denitrification in the anoxic fluvial estuary, followed by nitrification in the upper estuary (prior to oxygen regeneration). In addition, nitrogen was taken up during phytoplankton blooms in the lower estuary. Dissolved inorganic nitrogen species in porewaters from the upper 20 cm of sediments were obtained from a subtidal site in the middle of the lower estuary. Dissolved nutrient concentrations were low in the upper 10–15 cm of the sandy and organic poor (<1% POC) sediments mainly as a result of strong sediment mixing. The porewater profiles of ammonium and nitrate were evaluated quantitatively, using a one-dimensional steady-state diagenetic model. This coupled ammonium-nitrate model showed ammonification of organic matter to be restricted to the upper 4 to 7 cm of the sediments. Total nitrification ranged from 3.7–18.1 mmol m^?2 d^?1, converting all ammonium produced by ammonification. The net balance between nitrification and denitrification depended on the season. Nitrate was released from the sediments during winter but is taken up from the water column during summer. These results are in good agreement with data obtained from the independently calibrated water column model for the Scheldt Estuary (VAN GILSet al., 1993).     

Microenvironments and microbial community structure in sediments

The aim of this study was to explore the potential of a combined chemical and microbiological approach as part of a study of organic carbon oxidation processes in sediments. An assessment of microbiological diversity using molecular techniques was carried out in combination with high resolution chemical measurements at the sediment-water interface of a coastal lagoon affected by eutrophication in autumn 2000. There was a 0.2 mm overlap between the O2 and H2S profiles. pH showed a maximum just above the sediment-water interface coinciding with an oxygen maximum, suggesting photosynthetic activity, and a minimum coinciding with the O2-H2S interface. The redox potential was high in bottom water and surface sediment, reflecting the presence of oxygen and oxides, and reached low values after a step-wise decrease at -18 mm. Reduction of Fe occurred within the biofilm at the O2-H2S interface and was mostly due to reduction by H2S. The elevated concentrations of dissolved Mn in the oxic water may have been caused either by in situ production within organic aggregates or lateral water flow from sites nearby at which Mn2+ diffuses out of the sediment. Sequences related to sulphur chemolitotrophs were retrieved from the biofilm samples, which is consistent with the small overlap between O2 and H2S observed in this biofilm. Although the resolution of techniques used was different, sequencing results were consistent with chemical data in delineating the same horizons according to redox, pH or ecological properties.     

Bacterially mediated iron cycling and associated biogeochemical processes in a subtropical shallow coastal aquifer: implications for groundwater quality

Bacterially mediated iron redox cycling exerts a strong influence on groundwater geochemistry, but few studies have investigated iron biogeochemical processes in coastal alluvial aquifers from a microbiological viewpoint. The shallow alluvial aquifer located adjacent to Poona estuary on the subtropical Southeast Queensland coast represents a redox-stratified system where iron biogeochemical cycling potentially affects water quality. Using a 300 m transect of monitoring wells perpendicular to the estuary, we examined groundwater physico-chemical conditions and the occurrence of cultivable bacterial populations involved in iron (and manganese, sulfur) redox reactions in this aquifer. Results showed slightly acidic and near-neutral pH, suboxic conditions and an abundance of dissolved iron consisting primarily of iron(II) in the majority of wells. The highest level of dissolved iron(III) was found in a well proximal to the estuary most likely a result of iron curtain effects due to tidal intrusion. A number of cultivable, (an)aerobic bacterial populations capable of diverse carbon, iron, or sulfur metabolism coexisted in groundwater redox transition zones. Our findings indicated aerobic, heterotrophic respiration and bacterially mediated iron/sulfur redox reactions were integral to carbon cycling in the aquifer. High abundances of dissolved iron and cultivable iron and sulfur bacterial populations in estuary-adjacent aquifers have implications for iron transport to marine waters. This study demonstrated bacterially mediated iron redox cycling and associated biogeochemical processes in subtropical coastal groundwaters using culture-based methods.     

Seasonal changes in the microbial population of the water column and sediments of the Ongagawa River,northern Kyushu,Japan

The total viable count, population density of Escherichia coli and coliform bacteria, and nitrogen in the microbiomass (microbiomass-N) in sediments were monitored monthly at 12 points in the Ongagawa River basin from June 2002 to May 2006. The measurement of the sediment microbiomass-N was used for evaluation of the sediment’s microbial population in the river ecosystem. An extraordinarily high population of E. coli was observed during the season when there was stagnant water in the basin, with a high population and an insufficient drain diffusion system, and, thus hydrological water control is indispensable to prevent rapid E. coli growth. Microbiomass-N in sediments showed a negative correlation or independent fluctuation in relation to the bacterial population in the water column of the river. Seasonal changes in extracted nitrogen (N) in river sediments did not show correspondence with microbiomass-N in sediments. The microbiomass-N in sediments changed independently of the bacterial population in the river water, indicating that the high population of bacteria in the water does not lead to a high microbial population in river sediments. Ordination of the microbial parameters by canonical correspondence analysis (CCA) showed that microbiomass-N in sediments was quite different from other parameters. Relatively higher H⁺ (lower pH), PO₄ ³⁻ concentration and dissolved oxygen (DO) were the determinant parameters of higher microbiomass-N in sediments. A relative microbial abundance between the water column and sediments as well as each of the microbial populations in the water column and sediments could be a quantitative parameter for evaluating the biochemical processes of stream water.     

b型流感嗜血杆菌培养及细菌溶解产物制备工艺研究

目的研究b型流感嗜血杆菌(Haemophilus influenza type b,Hib)培养条件及细菌溶解产物制备工艺。方法比较Hib在传统培养基和改良培养基的生长情况,优化改良培养基在生物反应器中对Hib培养条件(p H值、温度、溶解氧等),研究最佳菌体细胞破碎方法及细菌溶解产物纯化制备工艺。结果改良培养基可代替传统培养基用于Hib的生产培养,且Hib在p H7.4、温度为36℃、溶解氧为25%的改良培养基中,生长迅速,菌体产量最高。高压匀浆破碎法的破碎效果明显优于超声波破碎法,破碎效果达到98%以上,纯化后的细菌溶解产物的多糖含量、总氮含量、蛋白质含量、核酸含量及细菌内毒素含量均符合《中华人民共和国药典》(三部)2010版中b型流感嗜血杆菌结合疫苗的质量标准。结论初步建立了b型流感嗜血杆菌培养及细菌溶解产物制备工艺。     

Diurnal depth-wise and seasonal changes of physico-chemical factors in Sathiar reservoir

The various physico-chemical factors such as rainfall, depth, water spread, temperature, dissolved oxygen, pH, redox potential, alkalinity, total phosphorus, nitrate, kjeldahl nitrogen and dissolved organic matter were studied both diurnally and seasonally and depth-wise for the period from April 1977 to March 1978. Consideration of physico-chemical factors indicates that they are inter-related. The main characteristics of Sathiar clearly indicate that it is highly eutrophic.     

Behavior of hydrogen peroxide in electrolyzed anode water

Oxygen electrodes and spectrophotometric analysis have been used to evaluate the contribution of H2O2, in addition to available chlorine, to the high redox potential of electrolyzed anode water (EAW) with potassium chloride as an electrolyte. H2O2 was added externally to EAW, and the reaction between H2O2 and the available chlorine in the water was examined. EAW has a low pH (2.5), a high concentration of dissolved oxygen, and extremely high redox potentials (19 mg/l and 1,319 mV) when the available chlorine is at the concentration of about 580 microM. The addition of H2O2 to EAW led to H2O2 decomposition, and the amount of oxygen produced was equivalent to the amount of available chlorine. Oxygen production was reduced by ascorbic acid, and completely inhibited by 600 microM ascorbate. The rate of oxygen production was much affected by pH, and was slowest at or near pH 5.0. Rates were particularly high in alkaline solution. Absorbance at 235 nm (pH 3.0 and 5.0) and 292 nm (pH 10.0) decreased when H2O2 was added to the EAW at these pHs, and the extent of decrease was similar pH dependency to that of the oxygen production rate. Oxygen was not produced after H2O2 was added to EAW at pH 2.6 when available chlorine was absent, but oxygen was produced after potassium hypochlorite was added to such EAW. The oxygen production rates in EAW without available chlorine at pH 5.0 and 2.0, pH adjustment with KOH and HCl, respectively, were faster than the rate at pH 2.6, and fastest at pH 2.0. These results suggest that H2O2 or hydroxyl radicals derived from Fenton's reaction did not contribute to the high redox potential of EAW prepared with chlorine compounds as an electrolyte, so that the decomposition of H2O2 occurred rapidly with the reactions of chlorine and hypochlorite ions in EAW.     

Physical background of the development of oxygen depletion in ice-covered lakes

The effect of the heat interaction between a water column and sediments on the formation, development, and duration of existence of anaerobic zones in ice-covered lakes is estimated based on observational data from five frozen lakes located in northwestern Russia and North America. A simple one-dimensional model that describes the formation and development of the dissolved oxygen deficit in shallow ice-covered lakes is suggested. The model reproduces the main features of dissolved oxygen dynamics during the ice-covered period; that is, the vertical structure, the thickness, and the rate of increase of the anaerobic zone in bottom layers. The model was verified against observational data. The results from the verification show that the model adequately describes the dissolved oxygen dynamics in winter. The consumption rates of DO by bacterial plankton and by bottom sediments, which depend on the heat transfer through the water–sediment interface, are calculated. The results obtained allow the appearance of potentially dangerous anaerobic zones in shallow lakes and in separate lake areas, which result from thermal regime changes, to be predicted. Priority programme of the German Research Foundation—contribution 10.     

The distribution of phosphate over iron-bound and calcium-bound phosphate in stratified sediments

Release of phosphate from, and adsorption ontosediments is calculated as a chemical equilibriumbetween dissolved o-phosphate and two solidphosphates, i.e. iron- and calcium-bound phosphate.Organic phosphates play a minor role, if any at all.Using chemical equilibrium equations, the distributionof the two solid inorganic phosphates is calculatedfrom the accumulated phosphate quantity as function oftime and depth in sediment layers of shallow lakes orwetlands. It is shown that this distribution dependson water depth, pH, Ca²⁺ concentration in thewater, Fe(OOH) concentration in the sediments andmaximal binding capacity of the sediments. Bycomparing values of dissolved phosphate at differentpH values, it is shown that acidification, whichusually takes place in hypolimnia, will cause releaseof phosphate, which is not necessarily dependent onthe redox potential. The release does depend on pH,Ca²⁺ concentration in the water, CaCO₃concentration in the sediments and the saturationstage of the two P-pools in the surface layers ofthese sediments. This revised version was published online in July 2006 with corrections to the Cover Date.     

Bioremediation of coal pile run off waters using an integrated microbial ecosystem

The pH of coal pile run off was elevated from <2 to >7 and dissolved heavy metal concentrations were brought within or below drinking water standards following batch treatments utilizing a mixed culture of bacteria. Treatment tanks containing the wastewater were inoculated with the bacterial culture and appropriate media for growth. Remediation (i.e. elevated pH, change in redox, and metal precipitation) occurred in both aerated and non-aerated treatment tanks inoculated with bacteria. The bacterial culture included specific strains of Bacillus and Pseudomonas. Remediation did not occur in treatment tanks containing growth nutrients alone. © Rapid Science Ltd. 1998     

Modelling faecal <Emphasis Type="Italic">streptococci</Emphasis> mortality in constructed wetlands implanted with <Emphasis Type="Italic">Eichhornia crassipes</Emphasis>

Faecal streptococci mortality was investigated in a water hyacinth (Eichhornia crassipes) constructed wetland pond. The wetland was 7.5 m long, 1.5 m wide and 1.0 m deep, and was implanted with E. crassipes. In order to assess the performance of the system towards bacterial mortality, a mathematical model, based on plug flow philosophy was developed. The model incorporated the role of factors, namely solar intensity, pH, dissolved oxygen, temperature, sedimentation, and root attached growth. Model analysis strongly suggests that bacterial mortality rate constant was largely influenced by two factors, namely solar intensity and root biofilm attachment, with both contributing approximately 70.5% of removal. The contribution of other factors like temperature, dissolved oxygen, pH and sedimentation on bacterial mortality rate were less significant. For example, dissolved oxygen, pH and sedimentation contributed 5%, 8% and 0.82%, respectively. Thus, the sedimentation factor was omitted from the model because of its insignificant contribution. The same was done for temperature, due to low ambient temperature range (3.1°C) in the study area. The overall model bacterial removal efficiency was 83%.     

Quantification of Tinto River sediment microbial communities: importance of sulfate-reducing bacteria and their role in attenuating acid mine drainage

Tinto River (Huelva, Spain) is a natural acidic rock drainage (ARD) environment produced by the bio-oxidation of metallic sulfides from the Iberian Pyritic Belt. This study quantified the abundance of diverse microbial populations inhabiting ARD-related sediments from two physicochemically contrasting sampling sites (SN and JL dams). Depth profiles of total cell numbers differed greatly between the two sites yet were consistent in decreasing sharply at greater depths. Although catalyzed reporter deposition fluorescence in situ hybridization with domain-specific probes showed that Bacteria (>98%) dominated over Archaea (<2%) at both sites, important differences were detected at the class and genus levels, reflecting differences in pH, redox potential, and heavy metal concentrations. At SN, where the pH and redox potential are similar to that of the water column (pH 2.5 and +400 mV), the most abundant organisms were identified as iron-reducing bacteria: Acidithiobacillus spp. and Acidiphilium spp., probably related to the higher iron solubility at low pH. At the JL dam, characterized by a banded sediment with higher pH (4.2 to 6.2), more reducing redox potential (-210 mV to 50 mV), and a lower solubility of iron, members of sulfate-reducing genera Syntrophobacter, Desulfosporosinus, and Desulfurella were dominant. The latter was quantified with a newly designed CARD-FISH probe. In layers where sulfate-reducing bacteria were abundant, pH was higher and redox potential and levels of dissolved metals and iron were lower. These results suggest that the attenuation of ARD characteristics is biologically driven by sulfate reducers and the consequent precipitation of metals and iron as sulfides.     

Biological,chemical and physical characteristics of downwelling and upwelling zones in the hyporheic zone of a north-temperate stream

Along a single stream riffle, there is a typical flow pattern in which surface water enters the hyporheic zone in a downwelling zone at the head of the riffle and hyporheic water returns to the stream surface in an upwelling zone at the tail of the riffle. Distinct patterns of physical and chemical conditions in the hyporheic zone are likely to determine patterns of microbial activity and occurrence of hyporheic fauna. Interstitial water and core samples were taken at three depths in the downwelling and upwelling zones of a single riffle in the Speed River, Southern Ontario, Canada. Physical and chemical characteristics of the hyporheic water, bacterial density, protein content, detritus content and faunal composition of the hyporheic sediment were analysed. The downwelling and upwelling zones differed significantly in temperature, pH, redox potential, dissolved oxygen and nitrate with significant positive correlations occurring among the latter three. There were no differences in bacterial density or detritus content between the two zones nor between depths in either zone, but protein content, considered to be a measure of biofilm biomass, was significantly higher in the downwelling zone. Total density of hyporheic fauna and the number of taxa decreased with increasing depth in both upwelling and downwelling zones, and were positively correlated with surface water characteristics (oxygen, temperature and nitrate), sediment protein content and detritus; however, only a weak correlation was found with zone. The composition of taxa differed between the two zones, and faunal distribution was correlated with dissolved oxygen, detritus, protein content and depth.