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The blooming of toxic cyanobacteria Microcystis in eutrophicated reservoirs causes serious difficulties for water supply worldwide. For the appropriate management of such reservoirs, a prediction model of toxic cyanobacteria Microcystis can be a useful tool. Therefore, this study aims to develop a Bayesian hurdle Poisson model for statistical prediction of toxic Microcystis from only two predictors, air temperature and trophic state index (TSI) calculated from chlorophyll-a. The gene copy number of the mcyB gene was used as a surrogate of toxic Microcystis cell density. The data on mcyB gene and chlorophyll-a were collected from 20 reservoirs in Nagasaki Prefecture (Japan). The daily average air temperature was downloaded from the local meteorological stations and a mean for 30 days before sampling date was calculated. The results showed that higher temperature and larger TSI accelerate the growth of toxic Microcystis. Furthermore, this model successfully predicted mcyB gene copy number as a surrogate of toxic Microcystis cell density for different conditions of air temperature and TSI with sufficient accuracy. Therefore, the proposed model has the potential to be a useful prediction tool for toxic cyanobacteria Microcystis in the integrated management of reservoirs.

Understanding the phytoplankton in aquaculture ponds is critical for proper pond management. Despite the importance, the relationships between phytoplankton composition, cultured fish type, season, and nutrients were not well understood. This study statistically investigated these relationships in aquaculture ponds. Data collected at 21 tilapia and 13 catfish ponds in September 2009 (wet season), December 2009 (cold season), and March 2010 (hot season) in northern Thailand were used for the analysis. The statistical analysis showed that PO4-P and NH4-N concentrations in catfish ponds were significantly higher than in tilapia ponds (p < 0.05, Wilcoxon test). The cyanobacterial abundance in catfish ponds was significantly greater than in tilapia ponds (p < 0.05, Wilcoxon test). In the hot season (March), green algae were abundant (p < 0.05), while cyanobacteria were depleted (p < 0.05). Multiple linear regression model was applied to determine important factors for statistically explaining cyanobacterial abundance. The result indicated that the best model selected by AICc included season and pond type as factors influencing cyanobacterial abundance but not nutrients. However, since the effect of nutrients was included in the difference in nutrient concentration due to the difference in fish species in the ponds, it was speculated that nutrients were insignificant as explanatory variables. Furthermore, it was hypothesized that cyanobacterial abundance was reduced in March (hot season) because the predation of cyanobacteria by tilapia may be encouraged at high temperature.

This study is a preliminary spatial-temporal assessment method of the ungauged catchment to determine the variation in water quality (WQ) and the land use influence on river basins’ health. The intermittent WQ data, the principal component analysis, and the redundancy analysis were used to evaluate the (dis)similarity among the 10 ungauged streams and their significance in the entire catchment. These revealed some similarities/differences in nutrient pollution and latent land-use influence on the streams’ health. There were similarities between R6-R7, R9-R10, among R1 to R4 basins, while R5 and R8 had distinct variances in their WQ dynamics. The intensive vegetable and rice production in R5, R7, R8, R9, and R10 basins were the major sources of high nutrient concentrations. The unique variations, especially in R5 and R8 basins could be attributed to other different pollution sources. Hence, it’s of great significance to carry out comprehensive research in the above 5 river basins. That is the efficiency of management practices, identification of pollution sources, and the extent to which the elevated nutrients in the streams interact with biota within the river regime. This research offers a method to evaluate WQ dynamics in relation to human interferences in river basins of a catchment with limited data under similar climatic conditions.

This paper presents a framework for mapping flow information from the gauged to the ungauged river basins. The calibration and validation of a hydrologic model were conducted to establish basic watershed characteristics. The new framework was then applied to account for the two watersheds' proportionality in their similarity, such as the influence of land use on transplanting flow signatures. Three land-use scenarios-discharges at the ungauged and gauged sites formed the basis of an equation mapping the gauged discharge signal to the ungauged site. In comparison with intermittent observed data, the framework prediction attained a precision of 0.85≥NSE≤0.95, 0.80≥R2≤0.94, 0.56≥bR2≤0.89. Despite considerable differences in the watershed area, slope, soils, and land cover, the framework satisfactorily depicted the variation in flow pulses of each river. In the absence of established hydrological information, this provides an alternative flow estimation at ungauged sites, reducing uncertainties in the regionalization of model parameters.

The use of low-cost agricultural waste-derived biochar in solving water and environmental challenges induced by climate change was investigated and sound conclusions were presented. Water reuse strategies can diminish the impact of climate change in rural and remote areas of developing countries. The novel biochar materials from three agro-waste biomass (Matamba fruit shell, Mushuma, and Mupane tree barks) were investigated and characterized to attest to their capacity to remove iodine from the aqueous solution. Their surface morphologies were assessed using Field Emission Scanning Electron Microscopy with Energy Dispersive X-Ray Spectroscopy (FESEM-EDX) which exhibited their structural phenomena to purge environmental pollutants. The Fourier-transform infrared spectroscopy (FTIR) was conducted to show surface functional groups of the biochar materials and Matamba fruit shell exhibited hydroxyl (-OH), carbonyl groups (C=O), C=C stretches of aromatic rings, and the carboxylate (C–O–O–) groups on its surface with corresponding data from the Isotherm and Kinetic models, statistically analyzed by the conventional and Bayesian methods. These surface mechanisms are said to be induced by weak van der Waals forces and - and -stacking interaction on the biochar surface. These adsorbents promised to be potential materials for environmental-ecosystem-protection and water re-use approach.

Biochar-inspired tertiary removal system is beneficial in preventing antibiotic residue discharged from hospital wastewater treatment. Taking advantage of a simple kiln controlled at around 600 °C, we succeeded in carbonizing corncobs to biochar with a surface area of 306 m2/g. Using ciprofloxacin (CFX), ofloxacin (OFX), and delafloxacin (DLX), we demonstrated the performance of the corncob biochar for the sorption removal. The pseudo-second-order rate of DLX was lower than CFX and OFX. The maximum sorption capacity Qmax of 93.9 μg/g for DLX, 399.6 μg/g for CFX, and 306.0 μg/g for OFX were estimated using the Langmuir model. The parameter KL relating to binding strength for DLX is 8 times larger than CFX and OFX. The Qmax could be mainly determined by the pore size distribution of the biochar and the dimensions of FQs considering hydration. Furthermore, we discussed that these results might relate to the number of halogen atoms and functional groups in the fluoroquinolones.

Remote communities in developing countries are facing ever-increasing water scarcities, due to cumulative demand induced by the climate change and global warming impacts. For the socio-economic and health well-being of the local communities, sufficient, efficient, and affordable water supply is fundamental from local-based adsorbents. Matamba Fruit shell was obtained and pyrolyzed to obtain well-transformed biochar, which exhibited enough capacity to remove Iodine from aqueous solution. The maximum capacity of adsorption of the Matamba Fruit shell was 2.122 mmol L

This report describes the whole-genome sequence of a microcystin-degrading bacterium, Novosphingobium sp. strain MD-1, isolated from a lake in Japan. The Novosphingobium sp. strain MD-1 genome had a total length of 4,617,766 bp. Moreover, strain MD-1 showed a conserved microcystin-degrading gene cluster (mlrA to mlrF), similar to Sphingopyxis sp. strain C-1.

Three individuals of Bdelloid rotifer (J1, J2 and J3) were isolated from a MBR system in Nagasaki University and one individual of rotifer (J4) in the original seed sludge collected from a wastewater treatment plant for the MBR was isolated. The four rotifer species were able to proliferate in toxic Microcystis cell suspension. The partial sequence of 18S rRNA gene of each isolated rotifer was determined using In-fusion cloning and searched by BLAST. The gene of the four rotifers J1, J2, J3 and J4 showed the same sequence, then the consensus sequence was in the branch of Bdelloid rotifers in the phylogenetic tree. Furthermore, a specific Bdelloid forward primer 55F and reverse primer 395R for real-time PCR was designed based on the consensus sequence for quantitative researches on the Bdelloid rotifers population. We succeeded to quantify the population of a Bdelloid rotifer cultured in toxic Microcystis cell suspension using the new designed primer pairs.

We have focused on membrane vibration in MBR to find an effective design for the reduction of membrane fouling. In the previous study, we developed a direct measurement method for membrane vibration of a hollow fiber membrane (HFM) using an accelerometer (ACM). In this study, we studied on vibration characters on an HFM bundle in a practical membrane module in MBR using the ACMs in a large transparent water tank. Three ACMs were attached at the middle (P1), top (P2) and bottom (P3) position along a center line in the HFM bundle in which air was supplied from a diffuser below the membrane module with different aeration rates from 0 to 250 L/min. The acceleration of membrane vibration time series for the X-axis direction (left-right displacement) and Z-axis direction (back-front displacement) was recorded at three positions. The average vibration amplitudes of the acceleration along both directions at each position were increased as the aeration rate was increased. The HFM bundle showed a collective vibration with a frequency peak between 0 and 50 Hz. The Z-axis motion character of HFM bundle is regarded as a sheet vibration. The obtained vibration character was useful for the new design of a membrane module in MBR against the membrane fouling.

Kandawgyi Lake is a famous recreational place in Yangon; however, the water quality deterioration and algae blooming occurred in recent years due to the economic development and people’s unawareness. In this study, the dynamic behaviors of water quality and mechanisms of eutrophication is investigated. During one-year field observation’s results showed that the lake’s water quality had been polluted by domestic wastewater depend on the high value of BOD and COD. Moreover, it was found that the thermal stratification exists about 1.0 meters water depth of the lake and anoxic water mass exists near the bottom of the lake. Besides, the one-year water depth observation showed the seasonal changes of water depth and, the water depth prediction by using the IOM mass balance model indicated better agreements in a dry season than a wet season. From the results of this study, it was thought that internal loading of nutrients could be the main reason of the algae blooms. Therefore, we proposed the bottom sediment removal as the most effective method to improve the water quality. Furthermore, small constructed wetlands at each inlet drains also can be an effective method as a countermeasure for the prevention of the next sediment accumulation.

Toxic cyanobacterial blooms frequently develop in eutrophic freshwater bodies worldwide. Microcystis species produce microcystins (MCs) as a cyanotoxin. Certain bacteria that harbor the mlr gene cluster, especially mlrA, are capable of degrading MCs. However, MC-degrading bacteria may possess or lack mlr genes (mlr+ and mlr− genotypes, respectively). In this study, we investigated the genotype that predominantly contributes to biodegradation and cyanobacterial predator community structure with change in total MC concentration in an aquatic environment. The 2 genotypes coexisted but mlr+ predominated, as indicated by the negative correlation between mlrA gene copy abundance and total MC concentration. At the highest MC concentrations, predation pressure by Phyllopoda, Copepoda, and Monogononta (rotifers) was reduced; thus, MCs may be toxic to cyanobacterial predators. The results suggest that cooperation between MC-degrading bacteria and predators may reduce Microcystis abundance and MC concentration.

Anaerobic Membrane Bioreactor (AnMBR) technology in recent years has been actively used for municipal and industrial wastewater treatment. Also, AnMBR technology has been considered as an alternative wastewater treatment application over conventional activated sludge system. AnMBRs are best possible operated with flat sheet, hollow fiber, or tubular membranes both in the microfiltration or in the ultrafiltration, but on ceramic membrane use has not been reported widely. AnMBRs are a desirable technology that needs additional research efforts and development. However, membrane fouling, which continues a major problem for all membrane bioreactors, seems much more serious under anaerobic than aerobic conditions. In this review, membrane fouling issues (including membrane fouling mechanism, classification, influent parameters, and mitigation) were discussed and summarized. Moreover, in fouling control, biogas sparging and recirculation (i.e. methane production) were addressed. Lastly, future research perspectives relating to its application and membrane fouling research are planned.

Environmental water ecosystems are facing serious hypoxia challenges because of high nutrient loadings from point and non-point sources. Therefore, the use of Vertical sub-surface flow constructed wetlands (VSSFCWs) for mitigating environmental water pollution through enhanced nitrification and denitrification processes. They offer a promising nutrient removal mechanism while also providing an ideal environment for the growth of perennial grasses. VSSFCWs not only play a role in providing safe sanitation, they produce biomass that can be harvested and used to produce fodder and biofuel in this complex global world. Biochar offers best habitation for microorganisms to decompose organic matter. The potential of constructed wetland biomass for bioenergy production through carbon sequestration had been observed. Planted with common reed macrophytes to promote biodiversity, the 0.251 m2 constructed wetland has been treating 0.03 cubic meter per day (CMD) of farm wastewater. The overall aboveground biomass was 1277 kg and total carbon content 471 kg at the peak of aboveground accumulation for the system emergent macrophyte. Incinerating of 80% biomass harvested of experimental area in an incineration plant could produce 2446 kWh for one month.

Antibiotics, widely known as major environmental xenobiotics, are increasingly being released into ecosystems due to their essential functions in human health and production. During the COVID-19 pandemic waves, antibiotic use increases remarkably in treating bacterial coinfections. Antibiotics were initially expected only to affect prokaryotes, but recent research has shown that they can disturb the biological systems of eukaryotes, especially vulnerable aquatic creatures, through both direct and indirect processes. However, their toxicity to the freshwater cladoceran Simocephalus vetulus, an essential link in the aquatic food web, has never been evaluated. The effects of four fluoroquinolones (ciprofloxacin: CFX, ofloxacin: OFX, gatifloxacin: GFX, delafloxacin: DFX), tetracycline (TET), and a mixture of these medicines (MIX) on S. vetulus thoracic limb rate (TLR) were examined in this study. After S. vetulus was exposed to 20 and 40 mg GFX L

Ciprofloxacin (CFX) and ofloxacin (OFX) are two of the most often used fluoroquinolone antibiotics, and their residues are found in large amounts in various aquatic settings. However, the toxicity tests of CFX using eukaryotic organisms such as Daphnia magna are inadequate, and the test result of OFX is currently unknown. Therefore, the chronic toxicity test for D. magna was performed during 42 days under exposure to CFX and OFX concentrations of 50, 500, and 5000 μg L−1. All exposure conditions did not cause mortality for D. magna. CFX exposure at 500 μg L−1 resulted in an earlier oogenesis date and increased brood size in the second birth. The Poisson-based generalized linear mixed-effects model revealed that the reduction of fertility was statistically significant for the CFX and OFX exposures at 5000 μg L−1. On the other hand, the production of dead eggs as offspring degradation was also found significantly as maternal D. magna exposed to antibiotics at 5000 μg L−1. In addition, following long-term exposure to antibiotics, maternal adaptation to antibiotics was established for offspring deterioration and fertility. However, the OFX exposure showed that the fertility-suppressed effects continued for a longer period than the CFX exposure. Although no rational explanation has yet been given for the more substantial effect of OFX on reducing fertility than CFX, molecular cell biology and symbiotic microbial flora derived from previous studies could explain our ecotoxicological results. This study is the first report for the OFX chronic toxicities on D. magna by comparing it to the toxicity of CFX. Our study contributes to guiding the future impact assessment of fluoroquinolone antibiotic pollution on ecosystems, including the need for new statistical methods in ecotoxicological studies.

This study aims to offer insights into how ciprofloxacin (CIP) impact bacterial community structures in the Sponge-MBR process when CIP is spiked into hospital wastewater. We found that the CIP toxicity decreased richness critical phylotypes such as phylum class ẟ-, β-, ɣ-proteobacteria, and Flavobacteria that co-respond to suppress denitrification and cake fouling to 37% and 28% respectively. Cluster analysis shows that the different community structures were formed under the influence of CIP toxicity. CIP decreased attached growth biomass by 2.3 times while increasing the concentration of permeate nitrate by 3.8 times, greatly affecting TN removal by up to 26%. Ammonia removal was kept stable by inflating the ammonia removal rate (p 0.003), with the wealthy Nitrospira genus guaranteeing the nitrification activity. In addition, we observed an increasing richness of Chloroflexi and Planctomycetes, which may play a role in fouling reduction in the Sponge-MBR. Therefore, if the amount of antibiotics in hospital wastewater continues to increase, it is so important to extend biomass retention for denitrification recovery.

We developed a novel fiber filtration system, which allows the filter bed packing density to be adjusted, to treat raw water of differing turbidities without coagulants. A bench-scale fiber filter is used to remove 5–20 μm poly(methyl methacrylate) particles with high efficiency, without the use of coagulants. The obtained data are analyzed using Yao’s model and regression models. The first filtration cycle achieved a benchmark removal efficiency of 90 % of 5 μm particles for 71 min with a Darcy velocity of 38.2 m/h. Each cycle included a backwash process, but the filtration time gradually decreased to about 46 min by the 5th cycle. However, pressure loss did not increase significantly during the filtration cycles. The shortening duration of filtration over operating successive cycles was postulated as residual particles remaining in the bed after backwash and rinsing. We measured pressure loss at various Darcy velocities for fiber filters with different packing densities and found that the square term of Darcy velocity in Ergun’s model was significant by the regression analysis. Based on the experimental results of the novel fiber filtration system, we compare the performance and running cost of a conventional fiber filtration system and a rapid sand filtration system. The novel fiber filtration system comprising 940 mm fiber filter elements at a packing density of 110 g/L removed 96 % of 5 μm particles at a Darcy velocity about four times greater than that of the rapid sand filter. The running cost of the novel fiber filter was estimated to be approximately one-sixth that of the conventional fiber filter using poly aluminum chloride and less than approximately 30 % of the sand filter.

The overall dioctyl terephthalate (DOTP) degradation efficiency during food waste composting was 98%. The thermophilic phases contributed to 76% of the overall degradation efficiency, followed by the maturation phase (22%), then the mesophilic phase (0.7%). The thermophilic phase had the highest specific degradation rate of 0.149 d-1. The progression of the bacterial community during the composting process was investigated to understand DOTP biodegradation. The results showed that the bacterial richness and the alpha diversity of the DOTP composting were similar to a typical composting process, indicating that the high concentration of DOTP did not hinder the thriving and evolution of the bacterial community. Additionally, Firmicutes was the most dominant at the phylum level, followed by Proteobacteria and Bacteroidetes. Bacilli was the most dominant class (70%) in the mesophilic phase, with the abundance decreasing thereafter in the thermophilic and maturation phase. Moreover, Lactobacillus sp. was the dominant species at the beginning of the experiment, which was probably responsible for DOTP biodegradation. The high removal efficiency observed in the maturation phase indicates that degradation occurs in all the composting phases, and that compost can be used to enhance natural attenuation. These findings provide a better understanding of the bacterial communities during biodegradation of DOTP and plasticizers via food waste composting and should facilitate the development of appropriate green bioremediation technologies.

The hydraulic loading rate (HLR) is a vital factor affecting the biological attached growth processes. Herein, a pilot-scale down-flow hanging sponge reactor (DHS) with a capacity of 0.5 m3/d was investigated under different HLRs (5.56 and 11.12 m3/m2.d). The DHS reactor was operated at an organic loading rate of 1.2 kgCOD/m sponge 3 .d. The results showed that COD removal attained 60.4 ± 11.4% at HRL of 5.56 m3/m2 d while this removal increased to 78% during the steady stage of operating at HLR of 11.12 m3/m2.d. Total suspended solid (TSS) was moderately removed with the efficiencies of 69.7%–75.6%. High NH 4 + -N removal of 80% was attained during operation, indicated that the nitrification process was mildly sensitive to change of HLR. This proposed technology brings a beneficial economic in decreasing energy consumption. This study suggested a viable treatment solution of the DHS using natural air ventilation, which favors low-income areas.

A microfluidic device with analytical chambers for electrochemical measurements has been employed to detect photosynthetic activity at single cell level. The flowing cells (Microcystis viridis) in a main channel are individually guided to the chamber with microelectrodes by an electrophoretic manipulation. The reduction current of oxygen was continuously monitored to determine the photosynthetic activity upon light irradiation. The average rates for oxygen generation were estimated and found to be 10(-18) mol/s level.

To predict outbreaks of infectious disease and to prevent epidemics, it is essential not only to conduct pathological studies but also to understand the interactions between the environment, pathogen, host and humans that cause and spread infectious diseases. Outbreaks of mass mortality in carp caused by Cyprinid herpesvirus 3 (CyHV-3), formerly known as koi herpesvirus (KHV), disease have occurred worldwide since the late 1990s. We proposed an environment–KHV–carp–human linkage as a conceptual model for “environmental diseases” and specify research subjects that might be necessary to construct and shape this linkage.

Alkali tolerance and the mechanism of microcystin (MC) degradation were investigated in the MC-degrading bacterial species, Sphingopyxis sp. C-1, to better understand the increased MC degradation under the alkaline conditions that arise during the disappearance of water blooms. MC-degrading bacteria harbour mlrA, mlrB and mlrC that encode MC-degrading enzymes. Sphingopyxis sp. C-1 also possesses these genes, as well as the mlrD gene that has been assumed to encode MC and its degradation transporter. This study demonstrated that MC degradation activity was promoted by the intermittent addition of microcystin-LR (MCLR) to cultures of strain C-1. That the expression of mlrA, mlrB and mlrC is induced by MCLR also was indicated, whereas that of mlrA and mlrB is induced by the MCLR degradation products linear MC, H-Adda-Glu-Mdha-Ala-OH (tetra peptide) and 2S, 3S, 8S, 9S-3-amino-9-methoxy-2, 6, 8-trimethyl-10-phenyldeca-4E, 6E-dienoic acid (Adda). Adda played a key role in the induction of mlrA and mlrB gene expression, and the cyclic structure of MCLR was closely associated with the induction of mlrC gene expression. It is suggested, therefore, that Adda is an essential part of a signalling molecule involved in cell-to-cell communication. Finally, the MC-degrading bacteria responded to MCLR and its degradation products by degrading the MlrA, MlrB and MlrC enzymes through a sequential chain reaction for the expression of each.

The littoral zone of lakes and lagoons is often used by fish for feeding or reproduction. However, the large changes in temperature that are typical of natural environments, including the littoral zone, represent a potential stressor for fish. Despite the importance of this habitat, little is known about the effect of daily temperature fluctuations on the stress responses of fish. We monitored daily temperature changes in the near-shore and offshore regions of a natural lagoon between May and July 2008–2010. We observed large temperature fluctuations more frequently in the near-shore zone than the offshore zone. We then exposed common carp (Cyprinus carpio) to a temperature regime similar to that observed in the near-shore zone and measured the levels of cortisol released into the water. The rate of cortisol release increased when carp were exposed to an increase in temperature of ~0.6°C/h over a 5-h period. Conversely, there was no change in the rate of release when temperatures decreased. Our results highlight the importance of maintaining high temporal resolution when evaluating the stress response to daily fluctuations temperature.

Electrochemical devices have been fabricated with 2 platinum (Pt) microelectrodes located at the bottom of microwells to characterize the photosynthetic activity of a single Microcystis viridis (cyanobacterium) cell. The cell was manipulated into the microwells by performing electrophoresis by applying dc voltage (typically 1.30 V peak-to-peak) to the Pt microelectrode. After removing the excess cells around the microwells, the microwells were covered using a urethane cover-plate, which blocked the diffusion of oxygen generated from the trapped cells thus leading to oxygen accumulation in the chamber. The cells trapped in the microwells were irradiated with a light-emitting diode light for 10 min to stimulate oxygen evolution by photosynthesis. The amount of oxygen accumulated in the chamber was determined by amperometry. The average rate of oxygen generation from a single cyanobacterium was calculated from the charge that was calculated from the responses and found to be at the level of 10−17 mol/s. Our system will be applicable to fundamental studies of cell biology and on-site monitoring of environmental toxicity.

Endocrine disruptors that act like hormones in the endocrine system might have toxic effects. Therefore, it is important to develop a portable device that can detect hormone active chemicals in samples rapidly and easily. In this study, a microfluidic device was developed for the detection of hormone active chemicals using genetically engineered yeast cells. The yeast cells were used as biosensors since they were genetically engineered to respond to the presence of hormone active chemicals by synthesizing beta-galactosidase (beta-gal). For achieving further sensitivity, we incorporated interdigitated array (IDA) electrodes (width, 1.2 microm; gap, 0.8 microm) with 40 electrode fingers into the analytical chamber of the microfluidic device. The yeast cells precultured with a hormone active chemical, 17beta-estradiol (E2), were trapped from the main channel of the device to the analytical camber by electrophoresis. After trapping in the analytical chamber, we performed electrochemical detection of beta-gal induced in the yeast cells with the IDA electrodes. Actually, electrochemical detection was performed on p-aminophenol that was converted from p-aminophenyl-beta-D-galactopyranoside with beta-gal. The electrochemical signals from the yeast cells precultured with 17beta-estradiol were successfully detected with the device. Furthermore, the inhibitory effects of antagonists such as tamoxifen were also detected electrochemically by using the device. Thus, the present microfluidic device can be used for highly sensitive detection of hormone active chemicals.

We microfabricated a novel device consisting of a 4 × 4 array microchamber sandwiched with the two microband electrode array. This device allows dielectrophoretic (DEP) manipulation of microbeads to introduce into and release out a certain address of the V-shaped microchamber, by applying AC voltage (10 Vpp, 10 kHz) on the basis of DEP forces. The design and the position of the two electrodes (row and column electrodes) at each microchamber were optimized by simulation based on a finite element method. More importantly, electrochemical generation-collection measurement was possible to evaluate enzymatic activity. After microbeads immobilized with glucose oxidase (GOD) was entrapped in the V-shaped microchamber with DEP, a measuring solution containing 3 mM ferrocenemethanol (FcCH2OH) and 0.1 M glucose was introduced. The medium in the V-shaped microwell was immediately exchanged into the measuring solution whereas microbeads stayed within the microwell without applying DEP voltage, because the flow within the microchamber was isolated from that of the main channel. Then the potential of the row and column electrodes were set at 0.5 and 0.1 V vs Ag/AgCl. The GOD activity can be monitored as the decrease in the [FcCH2OH]+ reduction current.

This report describes the whole-genome sequence of an alkalitolerant microcystin-degrading bacterium, Sphingopyxis sp. strain C-1, isolated from a lake in China.

mlrA is the only microcystin-degrading gene detected in Sphingomonas sp. MJ-PV. The gene has an extremely rare nucleotide sequence and homologous genes have not yet been discovered in the DNA database. We discovered the existence of a gene homologous to mlrA in new microcystin-degrading bacteria, MD-1 and Y2. These strains possessed mlrA homologues, and the identities of the genes of MD-1 and Y2 with the corresponding MJ-PV exceeded 98% and 84%, respectively. On the other hand, the mlrA gene was not detected in laboratory strains of the closely related Sphingomonas spp. strains employing hemi-nested polymerase chain reaction detection using two primer sets. Although the microcystin-degrading bacteria were closely related strains, they did not cluster together as the same species. We can conclude that the mlrA gene is conserved in three different bacterial species, and it is unique to microcystin degraders but not to the genus Sphingomonas.

The calculated value of microalgal massproductivity is an important parameter incommercial mass production and derivativecompound production. Mathematical analysiswas conducted in order to predict the rateof microalgal mass production, which wascalculated from the factor of oxygenevolution rate and the respiration rate percell. Calculated productivities of twomutants with small light-harvestingpigment, a phycocyanin deficient mutant ofSynechocystis PCC 6714 (strain PD-1)and a mutant with small light-harvestingpigment of Chlamydomonasperigranulata (strain LHC-1), wereevaluated compared with the wild-types ofthese mutants, respectively. The resultsshow that calculated productivity isimproved by reducing the content oflight-harvesting pigment, which issupported by the actual values ofphotosynthetic productivity. Productiveimprovement by reducing the content oflight-harvesting pigment is not limited toa special strain but applies to a widevariety of photosynthetic organisms.

A microcystin degradative bacteria was isolated from natural lakes and its phylogenetic position was confirmed. The 16 s rRNA of the bacteria exhibited 98.5% homology with the 16 s rRNA of Sphingomonas stygia belonging to the alpha subdivision on proteobacteria. The bacteria could degrade microcystins as a sole carbon source, therefore the bacteria utilizes microcystin. The bacteria could degrade microcystins LR, YR and RR, and their specific degradation rates were 0.66 h−1, 1.25 h−1 and 1.90 h−1, respectively. The degradation activity and growth rate of the bacteria was decreased under alkaline pH conditions.

In this study, effects of phosphorus concentration on aquatic microcosms were evaluated in terms of microbial population dynamics and the photosynthetic activity that is the starting point of the material flux. Microcosms that consist of algae Chlorella vulgaris, bacteria Pseudomonas putida and ciliate Cyclidium glaucoma were incubated using media that contain various concentrations of KH2PO4. At 14-16 days after the incubation started, sodium [14C] bicarbonate was added to each microcosm, and then microbial uptake of radioactive substrate was monitored. The population density of C. uulgaris and C. glaucoma increased, as initial phosphorus concentration was higher, while that of P.putida was constant. The photosynthetic activity of C. vulgaris also increased, as initial phosphorus concentration becomes higher. In the microcosm, P. putida uses metabolites produced by C. vulgaris and is preyed by C. glaucoma. Therefore, the growth activity of P.putida increased as the photosynthetic activity of C. vulgaris increased, but predation pressure by C. glaucoma also increased. Consequently, the population of P. putida kept constant. These findings lead to the conclusion that phosphorus concentration strongly affects the microbial population dynamics and material flux in the microbial loop in the aquatic ecosystem. However, the mass balance of each organism should keep steady state in the environment where the population of predator such as protozoa, invertebrates, fish and so on was kept suitable.

The biodegradability of microcystins produced by water-bloom was examined using the river die-away test. Although microcystin LR was not degraded during the first eight days after starting the test, after the eighth day, it began to be degraded rapidly, suggesting that microcystin LR was degraded by inductive metabolism and specific biodegradation. The activity of specific degradation of microcystin LR in the samples from a pond in which water-bloom was occurring was higher than from a pond with no water-bloom. Furthermore, the activity of specific degradation of microcystin LR in the samples taken during the water-bloom season (July 2001) was higher than on no water-bloom season (June 2001) . These results show that the bacteria that can degrade microcystin LR act accompanying the occurrence of water-bloom. Also, under the alkaline condition, microcystin LR was not degraded in the sample from the pond without water-bloom, but was degraded rapidly in the sample from the pond with water-bloom. We suggest that alkaliphilic or tolerant alkaline bacteria are strongly involved in the degradation of microcystin LR in the pond with water-bloom. We concluded that the fate of microcystin in the environment depend on specific bacteria which could adapt to two requirements, specific degradation metabolism for microcystin and tolerance to alkaline environment.

Potential for degradation of microcystin by biofilm was examined by some batch experiments using biofilm scraped from practical biological treatment facility combined with conventional treatment processes. The viable cells of Microcystis viridis, which produced microcystin LR, RR and YR were degraded at 6 to 10 days by the addition of biofilm. Biofilm collected in summer season had especially higher potential for degradation of Microcystis with complete degradation at 6 days. In all seasons, Monas spp. grew remarkably, accompanied with the higher decrease of the viable cells of Microcystis and the micro-animals were considered as a main predator for Microcystis cells. Intracellular microcystin LR, RR, YR were degraded simultaneously with high reduction of Microcystis cells. Dissolved microcystin LR of 1,000 μg l−1 was effectively degraded by indigenous aquatic bacteria on biofilm during 5 days, the degradability became higher with the increase in the concentration of microcystin LR. From the results of our research, it was clarified that the aggregated microorganisms consisting of biofilm had high potential for degradation of intracellular and dissolved microcystin.

In order to clarify the effect of the manganese released from lake sediment on the growth of M. aeruginosa, the cyanobacterium was cultured with leachate obtained by column leaching experiments which used lake sediment in Lake Kasumigaura Japan. The growth of M. aeruginosa in the leachate of sediment at St.1 and St.9 reached the density higher than 1.2×106 cells⋅ml-1, and was larger than those at the other points. The corresponding manganese concentrations of these leachates were also more than 10 times higher than the other points. That is why, it was considered that manganese might promote the growth of M. aeruginosa. Furthermore, in order to clarify the relation between manganese and the growth of M. aeruginosa, it was cultured with the addition of manganese into leachates of sediment and artificial medium. From the results, the addition of manganese or EDTA in all leachates of sediment except those for St.l and St.9, also accelerated the growth of M. aeruginosa. Moreover, it was obvious that manganese only promoted the growth of M. aeruginosa in the presence of EDTA, according to the results of experiments with artificial medium. A comparison of the results of experiments with leachate of sediment and artificial medium indicated that manganese complexing-agents like EDTA were included in the leachate of sediment. The relation between manganese and complexing-agents released from sediment is thus important for controlling the growth of M. aeruginosa in eutrophic lake.

In order to reduce favorably the growing Microcystis aeruginosa in eutrophicated lakes and marshes with no defective influence to aquatic ecosystem, suppression characteristics of M. aeruginosa in a model pond combined with bioreactor, in which predative microanimals, Monas guttula, Aeolosoma hemprichi and Philodina erythrophthalma were inoculated, was continuously examined. M. aeruginosa in the pond decreased slowly at early 2 days running, after the 4th day the reduction was clearly accerelated under hydraulic retention time of 8 hrs. For quantitative evaluation of the biomass-reduction, the reduction rate of M. aeruginosa in the lake was simulated by that of bioreactor with high densed micro-animals on the carrier. It was found that practical reduction rate of M. aeruginosa was ten-fold higher than theoretical value. As a reason for the significant reduction, it was considered that micro-animals released from the bioreactor combined with the lake might contribute the reduction.

To investigate the influence of materials released from lake sediment on the flora of phytop1ankton, we cultured three algal species, the green algae Scenedesmus acutus, the cyanobacterium Microcystis aeruginosa and filamentous cyanobacterium Oscillatoria agardhii with water obtained from an elution experiment of lake sediment. The effect of materials released from sediment on the growth of algae clearly varied from species to species of algae. The growth of green algae S. acutus was influenced by nitrogen released from sediment, though nitrogen was not actually supplied from the sediment somuch. The growth of filamentous cyanobacterium O. agardhii was mainly influenced by phosphorus released from the sediment. On the other hand, the growth of cyanobacterium M. aeruginosa was influenced by some materials, which were not nitrogen and phosphorus. From the results of an incubation experiment with adding EDTA and past research reports, it was suggested that these materials were organic complexes of iron, which stability constants was high, and inhibited M. aeurignosa from getting iron. This is a new finding in the relation between algae and lake sediment, and indicates that organic matter as complex-ligand released from sediment is one of the important factors affecting the flora of phytoplankton.