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PubMed2005

Diversity matters: dynamic simulation of distributed bacterial states in suspended growth biological wastewater treatment systems.

A MATLAB-based program was developed to simulate the distributions of states and behaviors of microbial storage product-accumulating bacteria in suspended growth systems. Currently available computer simulators of these systems predict dynamic behaviors by numerically solving differential biokinetic equations using average, or "lumped" system states (e.g., average microbial storage products concentrations). However, individual bacterial states are expected to diverge from average values, in part because individuals can have different hydrodynamic histories in terms of their residence times in upstream completely mixed flow reactors. The distributed state simulation program presented in this paper (DisSimulator 1.0) tracks individual bacteria as they move through a completely mixed reactor system. The program was evaluated for competition between polyphosphate-accumulating organisms (PAOs) and non-polyphosphate-accumulating heterotrophs in an enhanced biological phosphorus removal (EBPR) system for treatment of domestic wastewater. For identical systems and process conditions, simulations accounting for distributed states predicted larger anaerobic and aerobic solids residence time requirements for successful EBPR than did simulations using the lumped approach. One reason for this was that distributed simulations predicted large numbers of the PAOs were essentially inactive due to depleted or maximized storage product contents, while the lumped simulations predicted homogenous, 100% active PAO populations. Characteristic state profile shapes developed rapidly and were stable as total population numbers changed. Lumped state assumptions were demonstrated to produce large errors in predictions of EBPR system performance, and so consideration of distributed states may improve the accuracy of microbial storage products-based process simulations in systems with completely mixed hydrodynamics.

Bacterial Physiological Phenomena↗
PubMed1997

Emerging principles of inorganic nitrogen metabolism in Paracoccus denitrificans and related bacteria.

The taxonomy of Paracoccus denitrificans and related bacteria is discussed. Evidence is given which shows that the physiological differences between P. denitrificans and Thiosphaera pantotropha are less fundamental than previously thought. A proposal to consider a species P. pantotropha is mentioned. The properties of the denitrifying enzymes and the genes involved in their formation in P. denitrificans is discussed. The synthesis of the membrane-bound-nitrate reductase is regulated by FNR, that of the nitrite- and nitric oxide reductase by NNR. Evidence is given that FNR acts as a redox sensor rather than an oxygen sensor. The occurrence of aerobic denitrification and coupled heterotrophic nitrification-denitrification in the original strain of Thiosphaera pantotropha are explained by a limiting respiratory activity which activates FNR. Aerobic denitrification leads to a lower growth yield and an increase in mumax in batch culture when a limiting respiratory activity is assumed and when excess substrate is present. Coupled heterotrophic nitrification-denitrification gives a smaller increase in mumax and a more drastic reduction in yield. Both processes are thus advantageous to the organism. In a chemostat with limiting substrate these processes are disadvantageous. T. pantotropha has lost the ability for aerobic denitrification during extended cultivation. Possibly the substrate concentration was limiting during extended cultivation giving a selective advantage to variants which have lost these properties. The calculations predict that P. denitrificans should be able to grow chemolithotrophically with hydroxylamine.

Aerobiosis↗
PubMed2005

Organic matter released from activated sludge bacteria cells during their decay process.

Organic matter released from activated sludge bacteria is a considerable issue in the wastewater reclamation process. In this study, we focused 2-keto-3-deoxyoctulosonic acid in the Lipopolysaccharide existed in the gram-negative bacterial cell wall as an index of organic matter released from bacteria, and investigated the fate of 2-keto-3-deoxyoctulosonic acid in the aerated and ultrasonicated activated sludge samples. The results shows 1) 2-keto-3-deoxyoctulosonic acid concentration in the hydrolyzed sample was higher than non-hydrolyzed sample, and this implied that 2-keto-3-deoxyoctulosonic acid existed in the water phase as a monomer and also as a polymer such as Lipopolysaccharide form and their fragments; 2) the value of (2-keto-3-deoxyoctulosonic acid)/(dissolved organic carbon) ratio did not change in the sludge sonication process and was approximately 0.0006, on the other hand, in the bacteria decay process, the ratio varied from zero to approximately 0.0012; 3) the linear relationship was observed between the degraded heterotrophic biomass and the generated 2-keto-3-deoxyoctulosonic acid; and 4) 2-keto-3-deoxyoctulosonic acid might be considered as an index of organic matter originated from activated sludge bacteria cell.

Gram-Negative Bacteria↗
PubMedDate not supplied

Simulating forest productivity and surface-atmosphere carbon exchange in the BOREAS study region.

A process-based, general ecosystem model (BIOME-BGC) was used to simulate daily gross primary production, maintenance and heterotrophic respiration, net primary production and net ecosystem carbon exchange of boreal aspen, jack pine and black spruce stands. Model simulations of daily net carbon exchange of the ecosystem (NEE) explained 51.7% (SE = 1.32 g C m(-2) day(-1)) of the variance in daily NEE derived from stand eddy flux measurements of CO(2) during 1994. Differences between measured and simulated results were attributed to several factors including difficulties associated with measuring nighttime CO(2) fluxes and model assumptions of site homogeneity. However, comparisons between simulations and field data improved markedly at coarser time-scales. Model simulations explained 66.1% (SE = 0.97 g C m(-2) day(-1)) of the variance in measured NEE when 5-day means of daily results were compared. Annual simulations of aboveground net primary production ranged from 0.6-2.4 Mg C ha(-1) year(-1) and were concurrent with results derived from tree increment core measurements and allometric equations. Model simulations showed that all of the sites were net sinks (0.1-4.1 Mg C ha(-1) year(-1)) of atmospheric carbon for 1994. Older conifer stands showed narrow margins between uptake of carbon by net photosynthesis and carbon release through respiration. Younger stands were more productive than older stands, primarily because of lower maintenance respiration costs. However, all sites appeared to be less productive than temperate forests. Productivity simulations were strongly linked to stand morphology and site conditions. Old jack pine and aspen stands showed decreased productivity in response to simulated low soil water contents near the end of the 1994 growing season. Compared with the aspen stand, the jack pine stand appeared better adapted to conserve soil water through lower daily evapotranspiration losses but also exhibited a narrower margin between daily net photosynthesis and respiration. Stands subjected to water stress during the growing season may exist on the edge between being annual sources or sinks for atmospheric carbon.

Journal Article↗
PubMed1987

Light and acetate regulate a mitochondrial malate dehydrogenase.

A malate dehydrogenase was purified from the unicellular green alga Chlorogonium elongatum Dangeard. The enzyme was localized in the mitochondria by immunogold electron microscopy and was found to be present on the cristae. The concentration of the enzyme is regulated by acetate and light. In cells cultured heterotrophically with acetate as carbon source the activity and the concentration of the enzyme is 5- to 6-fold higher than in autotrophic cells. In mixotrophically cultured cells (light and acetate) the enzyme level attains only half of the value of that in heterotrophic cells. Acetate induces an increase of the enzyme concentration while light has an inhibitory effect on this process.

Journal Article↗
PubMed1987

Dynamics of extracellular DNA in the marine environment.

The production and turnover of dissolved DNA in subtropical estuarine and oligotrophic oceanic environments were investigated. Actively growing heterotrophic bacterioplankton (i.e., those capable of [3H]thymidine incorporation) were found to produce dissolved DNA, presumably through the processes of death and lysis, grazing by bacteriovores, and excretion. Production of dissolved DNA as determined by [3H]thymidine incorporation was less than or equal to 4% of the ambient dissolved DNA concentration per day. In turnover studies, the addition of [3H]DNA (Escherichia coli chromosomal) to seawater resulted in rapid hydrolysis and uptake or radioactivity by microbial populations. DNA was hydrolyzed by both cell-associated and extracellular nucleases, in both estuarine and offshore environments. Kinetic analysis performed for a eutrophic estuary indicated a turnover time for dissolved DNA as short as 6.5 h. Microautoradiographic studies of bacterial populations in Tampa Bay indicated that filamentous and attached bacteria took up most of the radioactivity from [3H]DNA. Dissolved DNA is therefore a dynamic component of the dissolved organic matter in the marine environment, and bacterioplankton play a key role in the cycling of this material.

Bacteria↗
PubMed1999

Variability of some microbial parameters in relation to the hydrological features of the water column in the Eolian Basin (Southern Tyrrhenian Sea).

During the EOCUMM '94 cruise, 15 stations located in the Eolian Islands area (Southern Tyrrhenian Sea) were sampled to analyse the distributions of the total bacterioplankton densities and the heterotrophic viable bacteria counts on Marine Agar 2216. According to the TS (temperature-salinity) diagrams, obtained by processing the CTD (conductivity-temperature-depth) vertical profiles, the sampled stations were grouped in "hydrological clusters". The bacteriological variables, together with the chlorophyll a and the particulate organic carbon measures obtained during the same cruise were used to compare the stations of the same and different clusters. The results indicated that variabilities of the analysed microbial parameters were not obviously related to the hydrographic features of the sampling stations. This work is an attempt to verify the possibility of using microbial parameters to characterize the structure of the water column.

Analysis of Variance↗
PubMed2004

Anoxic control of odour and corrosion from sewer networks.

Anoxic processes can effectively control odour and corrosion in sewer networks. However, the absence of fundamental knowledge on the kinetics of anoxic transformation of sewage prevents the engineering applications of anoxic control in sewers. This paper focuss on a basic understanding of the anoxic transformations needed for a conceptual simulation of the water phase processes. Experiments conducted in batch reactors have shown that nitrite builds up in wastewater during denitrification. Part of the nitrate-reducing biomass is capable of utilizing nitrite after nitrate is depleted. Compared with aerobic transformation, anoxic processes have low values of maximum growth rate of the biomass and also a low endogenous respiration rate. Heterotrophic yield determined under anoxic conditions, at level of 0.25 mmol e-eq (mmol e-eq)(-1), accounted for less than 40% of the corresponding aerobic values.

Bacteria, Anaerobic↗
PubMed2007

Hydrogen-dependent denitrification of water in an anaerobic submerged membrane bioreactor coupled with a novel hydrogen delivery system.

Hydrogen-dependent denitrification has gained significant attention due to its potential economic advantage over heterotrophic denitrification. However, effective hydrogen delivery and biomass retention under anaerobic conditions are significant challenges to implementation of this process. An innovative hydrogenotrophic denitrification system, that addresses these challenges, consisting of an anaerobic submerged membrane bioreactor (MBR) and a novel hydrogen delivery unit, was evaluated for removal of nitrate from a synthetic groundwater feed. The hydrogen delivery unit was designed to release hydrogen-supersaturated water to the reactor and was efficient in hydrogen delivery, providing complete mass transfer. The anaerobic submerged MBR was successful in both reducing nitrate from 25 mg NO(3)-Nl(-1) to below detection and separating biomass from treated water to produce effluent free of suspended solids. Nitrogen gas produced during denitrification was internally recycled to effectively achieve membrane scouring and reactor mixing. The total organic carbon was similar to that of the incoming feed water, averaging approximately 6 mgl(-1).

Anaerobiosis↗
PubMed2003

Nitrification, denitrification and biological phosphorus removal in piggery wastewater using a sequencing batch reactor.

Nutrients in piggery wastewater with high organic matter, nitrogen (N) and phosphorus (P) content were biologically removed in a sequencing batch reactor (SBR) with anaerobic, aerobic and anoxic stages. The SBR was operated with 3 cycles/day, temperature 30 degrees C, sludge retention time (SRT) 1 day and hydraulic retention time (HRT) 11 days. With a wastewater containing 1500 mg/l ammonium and 144 mg/l phosphate, a removal efficiency of 99.7% for nitrogen and 97.3% for phosphate was obtained. Experiments set up to evaluate the effect of temperature on the process showed that it should be run at temperatures higher than 16 degrees C to obtain good removals (> 95%). Batch tests (ammonia utilization rate, nitrogen utilization rate and oxygen utilization rate) proved to be good tools to evaluate heterotrophic and autotrophic biomass activity. The SBR proved to be a very flexible tool, and was particularly suitable for the treatment of piggery wastewater, characterized by high nutrient content and by frequent changes in composition and therefore affecting process conditions.

Animals↗
PubMed2004

Treatment of landfill leachate by a pilot-scale modified Ludzack-Ettinger and sulfur-utilizing denitrification process.

Nitrogen removal efficiency of a pilot-scale system consisted of Modified Ludzack-Ettinger (MLE) followed by sulfur-utilizing denitrification (SUDNR) process was evaluated with a landfill leachate. For SUDNR, a down-flow mode sulfur packed bed reactor (SPBR) filled with sulfur and limestone particles was used. Although total nitrogen removal efficiency of the MLE process was about 80% at the recycle ratio of 4, effluent contained 350-450 mg/L NO(3-)-N. Up to a loading rate of 1.2 kg NO(3-)-N/m3-day, the SPBR could achieve complete removal of nitrate, and nitrate removal rate was kept to that level even at higher loading rate. When a COD/N ratio of MLE process was maintained at 2 instead of 4, more organics with molecular weight less than 500 were utilized for heterotrophic denitrification although denitrification was not complete with the lack of electron donors. Clogging in the SPBR, mainly by the accumulation of nitrogen gas in the pores, could easily be removed by introducing the effluent in an upward direction for 1 min at 1 hr intervals. The proposed treatment system could achieve nitrate free effluent with a slight increase in chemical cost. Furthermore, depending on further COD removal requirement after biological treatment, the proposed treatment system can be an economical solution.

Bioreactors↗
PubMed2004

Thioredoxin links redox to the regulation of fundamental processes of plant mitochondria.

Mitochondria contain thioredoxin (Trx), a regulatory disulfide protein, and an associated flavoenzyme, NADP/Trx reductase, which provide a link to NADPH in the organelle. Unlike animal and yeast counterparts, the function of Trx in plant mitochondria is largely unknown. Accordingly, we have applied recently devised proteomic approaches to identify soluble Trx-linked proteins in mitochondria isolated from photosynthetic (pea and spinach leaves) and heterotrophic (potato tubers) sources. Application of the mitochondrial extracts to mutant Trx affinity columns in conjunction with proteomics led to the identification of 50 potential Trx-linked proteins functional in 12 processes: photorespiration, citric acid cycle and associated reactions, lipid metabolism, electron transport, ATP synthesis/transformation, membrane transport, translation, protein assembly/folding, nitrogen metabolism, sulfur metabolism, hormone synthesis, and stress-related reactions. Almost all of these targets were also identified by a fluorescent gel electrophoresis procedure in which reduction by Trx can be observed directly. In some cases, the processes targeted by Trx depended on the source of the mitochondria. The results support the view that Trx acts as a sensor and enables mitochondria to adjust key reactions in accord with prevailing redox state. These and earlier findings further suggest that, by sensing redox in chloroplasts and mitochondria, Trx enables the two organelles of photosynthetic tissues to communicate by means of a network of transportable metabolites such as dihydroxyacetone phosphate, malate, and glycolate. In this way, light absorbed and processed by means of chlorophyll can be perceived and function in regulating fundamental mitochondrial processes akin to its mode of action in chloroplasts.

Apoptosis↗
PubMed2001

Effect of ozonation and UV irradiation with direct filtration on disinfection and disinfection by-product precursors in drinking water treatment.

Pilot plant studies were conducted to evaluate the effect of pre-ozonation and ultraviolet irradiation on disinfection, disinfection by-product precursors and water quality in a direct filtration water treatment system. Disinfection parameters including total coliforms, faecal coliforms and heterotrophic plate count were investigated. Total organic carbon (TOC), trihalomethanes (THMs), total organic halides (TOX), filtered water turbidity and colour were also evaluated. It was found that advanced pre-oxidation processes (ozonation and UV irradiation) significantly increase the level of disinfection of raw water. Removal of total trihalomethanes and total organic halides precursors improved with ozonation and UV irradiation, compared to no oxidation treatment in direct filtration and/or in conventional water treatment. All coliforms (total and faecal) were completely destroyed by ozonation alone, and also with ozonation in conjunction with UV irradiation. However, the heterotrophic plate count was not significantly reduced at an ozone residual concentration of 0.1 mg l(-1). This suggests that disinfection efficiency is strongly influenced by competition reactions of organic and inorganic compounds with ozone. Precursors of total trihalomethanes and total organic halides were reduced by 90% and 98%, respectively, with advanced pre-oxidation processes. Water quality parameters were improved by the pre-ozonation and UV irradiation treatment system.

Disinfectants↗
PubMed1980

Uptake of D-glucose and L-proline by oligotrophic and heterotrophic marine bacteria.

The transport systems of the oligotrophic bacterium 486 for D-glucose and L-proline have been compared with those of the heterotrophic bacterium RP-303. Kinetic studies demonstrated that the rates of D-glucose and L-proline uptake by the two organisms were saturable processes. The apparent Km values of strain 486 for D-glucose and L-proline were 13.0 microM and 0.2 microM, respectively, whereas those of strain RP-303 were 3.2 microM for D-glucose and 1.8 microM for L-proline. Competition studies indicated that the D-glucose transport system of each bacterium was highly specific for D-glucose. The L-proline transport system of the oligotrophic bacterium 486 had a broad specificity, whereas that of the heterotrophic bacterium RP-303 had a narrow one.

Amino Acids↗
PubMed1985

Fate of recombinants of the rat mandibular epithelium with cranial ectomesenchymal cells of different sources in vitro.

The recombinants of the mandibular molar bud epithelia with cranial ectomesenchymal cell groups from several different sources--mandibular molar area, tongue anlagen, and lateral nasal process--were cultured. Dental laminalike buds were developed in each of the recombinants (incidence of development 38-86%). In the heterotrophic recombinants, heterotypic differentiation of mandibular epithelium was also induced. However, the foreign ectomesenchymal cells were not induced heterotypically by the epithelial genetic factor, but the mesenchymal genetic factor is maintained. It is suggested that mandibular molar bud epithelia have potency to proliferate into mesenchyme under non-organ-specific influences of ectomesenchymal cells and that presumptive mandibular mucosal epithelia have multipotency for differentiation sensitive to inductive influences by the heterotypic cranial ectomesenchymal cells but that the mandibular molar bud epithelia have no heterotypic inductive activity for the differentiation of cranial ectomesenchymal cells.

Animals↗
PubMed2002

Heterotrophic bacteria in the northern Adriatic Sea: seasonal changes and ectoenzyme profile.

A seasonal study of the quantitative and qualitative distribution of heterotrophic bacterial community was carried out in the Adriatic Sea between April 1995 and January 1996, in order to evaluate its spatial and temporal variability and metabolic potential in the degradation processes of organic matter. The culturable bacteria (CFU) ranged between 0.1 and 22% of total bacterioplankton with a maximum percentage in surface samples of coastal zones. Their distribution was generally affected by the prevailing hydrological conditions. At the coastal stations about 44-75% of CFU variance could be explained by river runoff. The changes in the composition of heterotrophic bacterial community showed a seasonal succession of main bacterial groups, with a prevalence of Gram negative, non fermenting bacteria in the cold period (April-January) and an increase of Vibrionaccae and pigmented bacteria in summer. The seasonal variations were more important at the stations influenced by rivers than offshore. The bacterial community showed a greater versatility for organic polymers hydrolysis in the offshore station than in the coastal areas. Over 60% of all isolated heterotrophic bacteria expressed peptidase, lipase and phosphatase ectoenzymes activities, in all seasons and showed an increasing trend in warm period (in July October). The alpha- and beta-glucosidase potentials of bacteria were lower (20% on average) and showed different pattern during the year. These results suggest different role of the bacterial community in the decomposition of organic matter in the Adriatic Sea. Since only 20% of bacterial strains expressed glucosidase activity, carbohydrate-rich polymers such as mucilage might accumulate.

Bacteria↗
PubMed2005

Effect of petrochemical sludge concentrations on microbial communities during soil bioremediation.

Qualitative and quantitative changes of microbial communities in soil microcosms during bioremediation were determined throughout one year. The soil was contaminated with 0%, 2.5%, 5%, 10% (wt/wt) of petrochemical sludge containing polynuclear aromatic hydrocarbons. We analyzed the hydrocarbon concentration in the microcosms, the number of cultivable bacteria using CFU and most probable number assays, the community structure using denaturing gradient gel electrophoresis, and the metabolic activity of soil using dehydrogenase activity and substrate-induced respiration assays. After one year of treatment, the chemical analysis suggested that the hydrocarbon elimination process was over. The biological analysis, however, showed that the contaminated microcosms suffered under long-term disturbance. The number of heterotrophic bacteria that increased after sludge addition (up to 10(8)-10(9) cells ml(-1)) has not returned to the level of the control soil (2-6 x 10(7) cells ml(-1)). The community structure in the contaminated soils differed considerably from that in the control. The substrate-induced respiration of the contaminated soils was significantly lower (approximately 10-fold) and the dehydrogenase activity was significantly higher (20-40-fold) compared to the control. Changes in the community structure of soils depended on the amount of added sludge. The species, which were predominant in the sludge community, could not be detected in the contaminated soils.

Biodegradation, Environmental↗
PubMed1970

Inhibitory Effect of Carbohydrate on Flowering in Lemna perpusilla: II. Reversal by Glycine and l-Aspartate. Correlation with Reduced Levels of beta-Carotene and Chlorophyll.

Flowering of Lemna perpusilla strain 6746 grown on 0.1 strength Hutner's medium in short days was inhibited by sucrose, glucose, fructose, and mannose, but not by various other sugars or metabolic intermediates. Only those sugars that inhibited flowering supported heterotrophic growth. Experiments with a single inductive long night indicated that an early stage in flowering was the sugar-sensitive process. Inhibition of flowering by carbohydrates was accompanied by reduced levels of chlorophyll and beta-carotene. The inhibitory effects of carbohydrates on flowering were partially reversed by iminodiacetate, glycine, and l-aspartate but not by d-aspartate, ethylenediaminetetraacetate, acetate, delta-aminolevulinic acid, or mevalonic acid. The possibility is discussed that carbohydrate repression of flowering and of chloroplast pigments resulted from inadequate levels of amino acids.

Journal Article↗