Accelerated biodegradation of nitrophenols in the rhizosphere of Spirodela polyrrhiza

We investigated the biodegradation of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP), and 2,4-dinitrophenol (2,4-DNP) in the rhizosphere of Spirodela polyrrhiza plants by conducting degradation experiments with three river water samples supplemented with each nitrophenol (NP). We then isolated NP-degrading bacteria both from the S. polyrrhiza roots and from the river water. In the river water samples, removal of the three NP was accelerated in the presence of S. polyrrhiza plants. The three NPs persisted in an autoclaved solution with sterile plants suggests that NP removal was accelerated largely by bacterial NP biodegradation rather than by adsorption and uptake by the plants. We isolated 8 strains of NP-degrading bacteria: 6 strains from the S. polyrrhiza roots and 2 strains from river water without the plants. The 2-NP- and 2,4-DNP-degrading bacteria were isolated only from the S. polyrrhiza roots. The 4-NPdegrading bacteria different from those isolated from the river water samples were also found on S. polyrrhiza roots. The 2-NP- and 4-NP-degrading strains isolated from the roots utilized the corresponding NP (0.5 mmol/L) as the sole carbon and energy source. The 2,4-DNP-degrading strains isolated from the roots showed substantial 2,4-DNP-degrading activity, but the presence of other carbon and energy sources was required for their growth. The isolated NP-degrading bacteria from the roots must have contributed to the accelerated degradation of the three NPs in the rhizosphere of S. polyrrhiza. Our results suggested that rhizoremediation with S. polyrrhiza may be effective for NP-contaminated surface water.     

A flow cytometer based protocol for quantitative analysis of bloom-forming cyanobacteria (Microcystis) in lake sediments

A quantitative protocol for the rapid analysis of Microcystis cells and colonies in lake sediment was developed using a modified flow cytometer, the CytoSense. For cell enumeration, diluted sediment samples containing Microcystis were processed with sonication to disintegrate colonies into single cells. An optimized procedure suggested that 5 mg dw (dry weight)/mL dilution combined with 200 W × 2 min sonication yielded the highest counting efficiency. Under the optimized determination conditions, the quantification limit of this protocol was 3.3×10⁴ cells/g dw. For colony analysis, Microcystis were isolated from the sediment by filtration. Colony lengths measured by flow cytometry were similar to those measured by microscopy for the size range of one single cell to almost 400 μupm in length. Moreover, the relationship between colony size and cell number was determined for three Microcystis species, including Microcystis flos-aquae, M. aeruginosa and M. wessenbergii. Regression formulas were used to calculate the cell numbers in different-sized colonies. The developed protocol was applied to field sediment samples from Lake Taihu. The results indicated the potential and applicability of flow cytometry as a tool for the rapid analysis of benthic Microcystis. This study provided a new capability for the high frequency monitoring of benthic overwintering and population dynamics of this bloom-forming cyanobacterium.     

Biodegradation of p-cresol by aerobic granules in sequencing batch reactor

The cultivation of aerobic granules in sequencing batch reactor for the biodegradation of p-cresol was studied. The reactor was started with 100 mg/L of p-cresol. Aerobic granules first appeared within one month of start up. The granules were large and strong and had a compact structure. The diameter of stable granules was in the range of 1-5 mm. The integrity coefficient and granules density was found to be 96% and 1046 kg/m³, respectively. The settling velocity of granules was found to be in the range of 2× 10^-2-6× 10^-2 m/sec. The aerobic granules were able to degrade p-cresol upto 800 mg/L at a removal efficiency of 88%. Specific p-cresol degradation rate in aerobic granules followed Haldane model for substrate inhibition. High specific p-cresol degradation rate up to 0.96 g p-cresol/(g VSS. day) were sustained upto p-cresol concentration of 400 mg/L. Higher removal efficiency, good settling characteristics of aerobic granules, makes sequencing batch reactor suitable for enhancing the microorganism potential for biodegradation of inhibitory compounds.     

Kinetic analysis and bacterium metabolization of α-pinene by a novel identified Pseudomonas sp. strain

Biodegradation has become a popular alternative remediation technology for its economic and ecological advantages. An aerobic bacterium (strain ZW) capable of degrading αup-pinene was isolated from a biofilter by a selective enrichment. Based on the 16S rRNA gene analysis and physiochemical properties, this strain was identified as Pseudomonas veronii. Under the optimized condition achieved by the response surface methodology (RSM), as well as pH 6.82, temperature 26.3\textcelsius and NaCl concentration 1.36%, almost 100% αup-pinene could be removed within 45 hr. Enzymatic biodegradation by the crude intracellular enzyme could be described well by the Michaelis-Menten model in which the maximum degradation rate V_max and the half-saturation constant K_m were calculated to be 0.431 mmol/(L. min) and 0.169 mmol/L, respectively. Activity assay of catechol suggested that the strain ZW possessed a catechol-1,2-dioxygenase and could decompose benzene-ring through ortho ring cleavage. Based on the identified intermediates by GC/MS, a new metabolic pathway was proposed, in which the final metabolites were some simpler organic and inorganic compounds. The present work demonstrated that the strain ZW would have a great application prospect for the remediation of αup-pinene-contaminated environment.     

Degradation of polycyclic aromatic hydrocarbons by Pseudomonas sp. JM2 isolated from active sewage sludge of chemical plant

It is important to screen strains that can decompose polycyclic aromatic hydrocarbons (PAHs) completely and rapidly with good adaptability for bioremediation in a local area. A bacterial strain JM2, which uses phenanthrene as its sole carbon source, was isolated from the active sewage sludge from a chemical plant in Jilin, China and identified as Pseudomonas based on 16S rDNA gene sequence analysis. Although the optimal growth conditions were determined to be pH 6.0 and 37℃, JM2 showed a broad pH and temperature profile. At pH 4.5 and 9.3, JM2 could degrade more than 40% of fluorene and phenanthrene (50 mg/L each) within 4 days. In addition, when the temperature was as low as 4℃, JM2 could degrade up to 24% fluorene and 12% phenanthrene. This showed the potential for JM2 to be applied in bioremediation over winter or in cold regions. Moreover, a nutrient augmentation study showed that adding formate into media could promote PAH degradation, while the supplement of salicylate had an inhibitive effect. Furthermore, in a metabolic pathway study, salicylate, phthalic acid, and 9-fluorenone were detected during the degradation of fluorene or phenanthrene. In conclusion, Pseudomonas sp. JM2 is a high performance strain in the degradation of fluorene and phenanthrene under extreme pH and temperature conditions. It might be useful in the bioremediation of PAHs.     

Study on the cytoplasmic incompatibility in some natural population of Culex pipiens complex in China and Japan

The cytoplasmic incompatibility in the field population of Culex pipiens complex from China and Japan was studied. The results of the crossing experiments between 11 different strains suggest that some Japanese strains might be possible to be used for control Chinese strains by using male sterile technique, and the heavy infection of wolbachiae in mosquitoes may have some relations with the cytoplasmic incompatibility in the field population of Cx. pipiens complex.     

Degradation of pyrene by immobilized microorganisms in saline-alkaline soil

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) is very difficult in saline-alkaline soil due to the inhibition of microbial growth under saline-alkaline stress. The microorganisms that can most effectively degrade PAHs were screened by introducing microorganisms immobilized on farm byproducts and assessing the validity of the immobilizing technique for PAHs degradation in pyrene-contaminated saline-alkaline soil. Among the microorganisms examined, it was found that Mycobacterium sp. B2 is the best, and can degrade 82.2% and 83.2% of pyrene for free and immobilized cells after 30 days of incubation. The immobilization technique could increase the degradation of pyrene significantly, especially for fungi. The degradation of pyrene by the immobilized microorganisms Mucor sp. F2, fungal consortium MF and co-cultures of MB+MF was increased by 161.7% (P < 0.05), 60.1% (P < 0.05) and 59.6% (P < 0.05) after 30 days, respectively, when compared with free F2, MF and MB+MF. Scanning electron micrographs of the immobilized microstructure proved the positive effects of the immobilized microbial technique on pyrene remediation in saline-alkaline soil, as the interspace of the carrier material structure was relatively large, providing enough space for cell growth. Co-cultures of different bacterial and fungal species showed different abilities to degrade PAHs. The present study suggests that Mycobacterium sp. B2 can be employed for in situ bioremediation of PAHs in saline-alkaline soil, and immobilization of fungi on farm byproducts and nutrients as carriers will enhance fungus PAH-degradation ability in saline-alkaline soil.     

Dimethyl phthalate biodegradation by Dunaliella tertiolecta

Dunaliella tertiolecta has an ability to biodegrade dimethyl phthalate(DMP) was found in this study, and the average of the biodegradation rates were 11.3 mg/(L·d) and 30.5 mg/(L·d), and the average of the phthalic acid (PA) production rates were 1.5 mg/(L·d) and 3.6 mg/(L·d), for initial 100 mg/L and 300 mg/L DMP, respectively. The larger amount of accumulation by D. tertiolecta under higher DMP concentration may be responsible for the increase of biodegradation rate, and one of products of DMP biodegradation by D. tertiolecta may be PA. By fitting the process of DMP biodegradation by D. tertiolecta with a kinetic equation newly suggested, the standard deviations between calculated and observed values were 2.5 mg/L and 5.7 mg/L, respectively.     

Removal of sulfamethazine antibiotics by aerobic sludge and an isolated Achromobacter sp. S-3

Removal characteristics of sulfamethazine (SMZ) by sludge and a bacterial strain using an aerobic sequence batch reactor (ASBR) were studied. Operating conditions were optimized by varying the reaction time and sludge retention time (SRT). An Achromobacter sp. (S-3) with the ability to remove SMZ was isolated from the ASBR. The effects of different operating parameters (pH and temperature) on the biodegradation of SMZ by S-3 were determined. The results indicate that, between 0.5 and 4 hr, reaction time of the ASBR had a significant effect on the SMZ removal efficiency in the system. The SMZ removal efficiency also increased from 45% to 80% when SRT was prolonged from 5 to 25 days, although longer SRT had no impact on SMZ removal. The SMZ adsorption rate decreased with increasing temperature, which fitted Freundlich isotherm well. The removal of SMZ in the ASBR was due to the combined effects of adsorption and degradation, and degradation played a leading role.     

Start-up of the anammox process from the conventional activated sludge in a hybrid bioreactor

The anaerobic ammonium oxidation (anammox) process was successfully started up from conventional activated sludge using a hybrid bioreactor within 2 months. The average removal efficiencies of ammonia and nitrite were both over 80%, and the maximum total nitrogen removal rate of 1.85 kg N/(m³.day) was obtained on day 362 with the initial sludge concentration of 0.7 g mixed liquor suspended solids (MLSS)/L. Scanning electron microscope (SEM) observation of the granular sludge in the hybrid reactor clearly showed a high degree of compactness and cell sphericity, and the cell size was quite uniform. Transmission electron microscope photos showed that cells were round or oval, the cellular diameter was 0.6--1.0 μupm, and the percentage of the anammoxosome compartment was 51%--85% of the whole cell volume. Fluorescence in situ hybridization analysis (FISH) indicated that anammox bacteria became the dominant population in the community (accounting for more than 51% of total bacteria on day 250). Seven planctomycete 16S rRNA gene sequences were present in the 16S rRNA gene clone library generated from the biomass and affiliated to Candidatus Kuenenia stuttgartiensis and Candidatus Brocadia sp., a new anammox species. In addition, the average effluent suspended solid (MLSS) concentrations of outlets I (above the non-woven carrier) and II (below the non-woven carrier) were 0.0009 and 0.0035 g/L, respectively. This showed that the non-woven carrier could catch the biomass effectively, which increased biomass and improved the nitrogen removal rate in the reactor.     

Responses of activities, abundances and community structures of soil denitrifiers to short-term mercury stress

The responses of activities, abundances and community structures of soil denitrifiers to mercury (Hg) stress were investigated through a short-term incubation experiment. Four soil treatments with different concentrations of Hg (CK, Hg25, Hg50, and Hg100, denoted as 0, 25, 50, and 100 mg Hg/kg dry soil, respectively) were incubated for 28 days. Soil denitrification enzyme activity (DEA) was measured at day 3, 7 and 28. The abundances and community structures of two denitrification concerning genes, nirS (cd₁-nitrite reductase gene) and nosZ (nitrous oxide reductase gene), were analyzed using real-time PCR and denaturing gradient gel electrophoresis (DGGE). Results showed that soil DEA was significantly stimulated in the treatments of Hg25 and Hg50 compared with others at day 7. Meanwhile, no difference in the abundances of soil nirS and nosZ was found between Hg spiked treatments and CK, except the lower abundance of nirS (P<0.05) in the Hg added treatments compared with that in the CK at day 28. The community structures of denitrifiers based on nirS gene presented obvious change at day 7 along with the Hg additions, however, no variation was found in all treatments based on the nosZ gene. The results indicated that Hg (Hg25 and Hg50) had a strongly short-term stimulation on soil DEA, and nirS gene is more sensitive than nosZ gene to Hg stress.     

Effects of alternating temperatures on development and reproduction of the armyworm,Mythimna separata (Walker)

Effects of cycling and constant temperature on development and reproduction of the armyworm, Mythimna separata (Walker) were investigated by rearing the insects on the artificial diet under temperatures covering low(16-24℃ vs. 20 ℃ ), medial(20-28℃ vs. 24℃ ) and high(24-32 ℃ vs. 28 ℃) regions. In the low region, all the immature stages of the insect developed significantly faster under alternating temperatures than at corresponding constant temperatures. For the medial region, their development was little affected by variable temperatures. For the high region, developmental durations tended to be longer under cycling temperatures except egg stage.Mean fecundities of the adult moths markedly increased under cycling temperatures as compared with those at respective constant temperature in all regions.Possible reasons for effect of alternating temperatures on insect development are discussed in some details.     

Spatial heterogeneity of cyanobacterial communities and genetic variation of Microcystis populations within large, shallow eutrophic lakes (Lake Taihu and Lake Chaohu, China)

Cyanobacteria, specifically Microcystis, usually form massive blooms in eutrophic freshwater lakes. Cyanobacterial samples were collected from eight sites of both Lake Taihu and Lake Chaohu in late summer to determine the diversity and distribution pattern of cyanobacteria and Microcystis in large, shallow, entropic lakes with significant spatial heterogeneity and long-term Microcystis bloom. Molecular methods based on denaturing gradient gel electrophoresis and clone library analysis were used. A similar heterogeneous distribution pattern of cyanobacteria in both lakes was observed. Most parts of these two lakes with high trophic level were dominated by Microcystis. However, in the regions with low trophic levels as well as low concentrations of chlorophyll a, Synechococcus occupied a considerable percentage. Different morphospecies and genotypes dominated the bloom-forming Microcystis populations in these two lakes. Microcystis viridis and Microcystis novacekii were dominant in Lake Chaohu, whereas Microcystis flos-aquae was dominant in Lake Taihu. Only 2 of the13 Microcystis operational taxonomic units were shared between these two lakes. Analysis of molecular variance based on 16S to 23S internal transcribed spacer sequences indicated the significant genetic differentiation of Microcystis between these two lakes (F_st = 0.19, p < 0.001). However, only 19.46% of the genetic variability was explained by the population variation between lakes, whereas most (80.54%) of the genetic variability occurred within the lakes. Phylogenetic analysis revealed no phylogeographic structure of Microcystis population in these two lakes, as illustrated by their cosmopolitan nature. Our results revealed that spatial heterogeneity within lakes has more impact on the cyanobacterial diversity than geographical isolation in a local scale.     

Competition of the active roots of Cassia siamea Lam. and Zea mays L.(cv.Katumani Composite B) in an alley cropping trial in semi arid Kenya

A study on root competition in alley cropping was carried out in an agroforestry system, involving Cassia siamea Lam. and maize ( Zea mays L. cv. Katumani composite B). The existence and intensity of root competition in the top soil as manifested by the distribution of the active roots of cassia and maize, in space and time, was assessed. The root length density of maize was far greater than that of cassia in the upper 10 cm, implying that cassia was not competing with maize for water and/or nutrients at that depth. However, at maize crop tasselling and grain filling stages there was a marked overlap of roots of the two plants at lower depths (20—50 cm). This varied with distance from the cassia hedge in a way that there was a tendency for highest overlap near middle maize rows. This partly explained observed yield differences. Therefore cassia may not be a suitable choice for alley cropping with maize under semi-arid conditions on non-sloping land, unless most of its active roots can be properly managed to absorb resources below the feeding rhizosphere of the active maize roots.     

Performances of the cotton bollworm,Heliothis armigera (Hubner) at different temperatures and relative humidities

The cotton bollworm, Heliothis armigera (Hubner) is an important insect species at-tacking many crops. Their performances have been examined at temperatures from 15℃ to 35℃ and relative humidities (RH) between 22.5% and 100%, respectively, in order to assess possible effect of climate in future on its occurrence and infestation. Durations of all developmental stages of the insect shortened with increasing temperature. The temperature favoring population growth ranged from 25℃ to 30℃.Larval duration and adult longevity decreased as relative humidity increased, but development of other stages was independent of RH. At RH of over 64%, their survival rate, egg production and oviposition rate varied a little, and all the population parameters of the insect remained at a relative constant level.     

Effect of SO2 on performance of the turnip moth,Agrotis segetum Schiff

Effect of SO₂-enriched air on the turnip moth, Agrotis segetum Schiff.was investigated by rearing the larvae on rape leaves that had been exposed to 40 or 80 ppb of the air pollutant in field fumigation chambers. An examination on the 11th day showed that the larvae in both treatments survived more, developed markedly faster, their fresh v/eig'ht and mean relative growth rate were significantly greater than those of control insect. Improvement of their growth and development resulted in decrease of total larval duration by 0.5 - 1.0 day. Pupal and adult performances were little affected by SO₂ level to which larval food plant was exposed. Possible reason responsible for enhanced growth and development of the insect species was discussed.     

Effects of Cd2+ on the nucleolus in root tip cells of Allium cepa

The effects of different concentrations of cadmium chloride ranging from 0.5 to 20 ppm on the nucleolus in root tip cells of Allium cepa were studied using the silver staining technique. The results indicated that after the treatment with Cd²⁺,different changes in nucleolar morphology appeared. The nucleolar material was extruded from the nucleus into the cytoplasm,and the nucleoli at mitotic metaphase did not disappear. Apparently,cadmium showed a specific effects on the nucleoli in root tip cells of Allium cepa. The possible mechanism behind this phenomenon is also briefly discussed.     

Hydrolysis of l-(2-chlorobenzoy|)-3-(4-chlorophenyl) urea in aquatic system

The degradation of the insect growth regulator 1-(2-chlorobenzoyl)-3-(4-chlorophenyl)urea (CCU)was studied both in distilled water and in buffer solution．The experimental results indicated that CCU is not stable in aqueous solution and easily decomposes in alkaline water．At pH 6 and pH 10，the half lives (T_v2)of hydrolysis arc about 9 days and 2 days，respectively．The rate of hydrolysis increases as either the concentration of alkalinity or temperature increases．At [NaOH]=0.01865 mol/L，with every lO^oC increase in temperature，the reaction rate increases about 3 times．the activation energy for hydrolysis is 7l.56 kJ/mol．Basic catalyzed degradation of CCU at levels greatly above its solubility in water resulted in rapid degradation to as many as four identified products：(4-chlorophenyl)urea，2-chlorobenzoic acid，2-chlorobenzamide，and 4-chloroaniline．The major products were(4-chlorophenyl)urea and 2-chlorobenzoic acid．     

Integrated assessment of biochemical responses in Mediterranean crab (Carcinus maenas) collected from Monastir Bay, Tunisia

The biochemical response of Mediteranean Crab (Carcinus maenas) collected at five stations of Monastir Bay and from Kuriat station as control was studied using a set of complementary biomarkers. The catalase, glutathione S-transferase, lactate dehydrogenase, acetycholinesterase activities; and metallothionein and malonediladehyde levels in gills were evaluated. Results revealed differences among sites in relation to each specific biomarker. Hence, a suite of biomarkers can be used to discriminate sampling sites according to types of pollution, reflecting differing conditions of anthropogenic impact. Based on Integrated Biomarker Response, the highest values and critical biochemical alteration were observed at Khniss and Ksibat in response to urban and industrial discharges and the lowest IBR value was found at reference site. The current study has shown clearly that a biomarker-based index is usefulness tool in the monitoring Tunisian coast using C. maenas as sentinel specie. Further studies in progress to investigate the seasonal variations of IBR levels and its relationship to pollutants concentrations in the sediment, gills and digestive gland of Carcinus maenas from Monastir Bay.     

Effects of two polybrominated diphenyl ethers (BDE-47, BDE-209) on the swimming behavior, population growth and reproduction of the rotifer Brachionus plicatilis

Polybrominated diphenyl ethers (PBDEs) are new kinds of persistent organic pollutants (POPs) and their potential threats to the equilibrium and sustainability of marine ecosystems have raised worldwide concerns. Here, two kinds of PBDEs, tetra-BDE (BDE-47) and deca-BDE (BDE-209) were applied, and their toxic effects on the swimming behavior, population growth and reproduction of Brachionus plicatilis were investigated. The results showed that: (1) The actual concentrations of BDE-47 and -209 in the seawater phase measured by GC-MS (Gas Chromatography-Mass Spectrometer) were much lower than their nominal concentrations. (2) In accordance with the 24-hr acute tests, BDE-209 did not show any obvious swimming inhibition to rotifers, but a good correlation did exist between the swimming inhibition rate and BDE-47 concentration suggesting that BDE-47 ismore toxic than BDE-209. (3) Both BDE-47 and -209 had a significant influence on the population growth and reproduction parameters of B. plicatilis including the population growth rate, the ratio of ovigerous females/non-ovigerous females (OF/NOF), the ratio of mictic females/amictic females (MF/AF), resting egg production and the mictic rate, which indicate that these parameters in B. plicatilis population were suitable for monitoring and assessing PBDEs. Our results suggest that BDE-47 and -209 are not acute lethal toxicants and may pose a low risk to marine rotifers at environmental concentrations for short-term exposure. They also accumulate differently into rotifers. Further research data are needed to understand the mechanisms responsible for the effects caused by PBDEs and to assess their risks accurately.