Degradability of Treated Ethion Insecticide by TiO2 Photocatalysis.

Ethion, an insecticide, is widely used with fruit and vegetable crops. This research studied the reduction and oxidative degradation of standard ethion by TiO2 photocatalysis. A standard ethion solution (1 mg L(-1)) was treated with different concentrations of TiO2 powder (5, 10, 20, 40 and 60 mg mL(-1)) for 0, 15, 30, 45 and 60 min. The amount of ethion residue was detected by gas chromatography with flame photometric detection (GC-FPD) and the concentration of anions produced as major degradation products was determined by Ion Chromatography (IC). The TiO2 photocatalysis efficiently reduced ethion concentrations, with the highest degradation rate occurring within the first 15 min of reaction. The reaction produced sulphate and phosphate anions. The TiO2photocatalysis reduced 1 mg L(-1) ethion to 0.18 mg L(-1) when treated with 60 mg mL(-1) TiO2 powder for 60 min. The lethal concentration (LC50) of standard ethion was also estimated and compared to the treated ethion. All treatments, especially 60 mg mL(-1) TiO2 powder, markedly detoxified ethion, as tested with brine shrimp (Artemia salina L.), with an LC50 value of 765.8 mg mL(-1), compared to the control of 1.01 mg mL(-1).

Sequence analysis of cDNAs encoding the heavy and light chain variable regions of a WSSV-neutralizing monoclonal antibody.

Antibodies raised against individual viral envelope proteins have been used in white spot syndrome virus (WSSV) neutralization assays. We report here the sequence analysis of cDNAs encoding the variable regions of a novel monoclonal antibody that binds to the viral envelope protein and neutralizes WSSV infection. The heavy and light variable chains are most homologous to VH7183 germline gene (AF120472) and IgVk RF germline gene (AJ235936), respectively. Database searches using the derived sequences predicted residues comprising CDR loops. The 12 amino acid residue of the heavy chain CDR3 is rich in negatively charged aspartic acid (25%) and did not show significant homology to any murine V gene available on the database. This study provides insights on the paratope-epitope interaction and can be used to identify compounds with comparable properties as the paratope leading to future development of drugs and vaccines for WSSV infection.

Detection of White spot syndrome virus DNA in pond soil using a 2-step nested PCR.

White spot syndrome virus (WSSV) continues to be the most pathogenic among the penaeid shrimp viruses. In this study, WSSV DNA was detected in pond soil samples using a 2-step nested PCR. Primers described previously were used for the first round of amplification and based on the sequenced amplicon, an inner primer was designed for the 2nd round of amplification. Using plasmid DNA (pET 100) containing the 211 bp target WSSV sequence, analytical sensitivity showed that the 2-step nested PCR protocol was able to detect down to 0.015 fg of the plasmid DNA, or approximately 2 copies of the target DNA sequence. Persistence of WSSV DNA in pond soil samples after various time intervals was determined. WSSV-specific PCR product (161 bp) was still present in the soil samples even after 10 months of storage. The effect of soil heat treatment on the WSSV DNA was also examined. Soils were subjected to 25, 37, 50 and 70 degrees C for 1, 3 and 5 days. The results showed that PCR amplifiable WSSV DNA was still present even after 5 days at 70 degrees C. To our knowledge, this is the first report on the detection of WSSV DNA in soil samples. Based on these findings, it is concluded that the persistence of viral DNA in soil habitats may be an important aspect of WSSV ecology and may have an implication for viral transmissibility.

Changes in chlorinated organic pollutants and heavy metal content of sediments during pyrolysis.

BACKGROUND: There has been an increasing concern about the treatment and disposal of contaminated sediment from dredged rivers, harbors or estuaries due to the accumulated toxic organics such as dioxins and inorganics, particularly heavy metals like Cr, Pb, Zn, Cu, Hg and Cd. However, considering the huge amount of materials and financial costs involved, any candidate technology must ultimately result in reusable, residual by-products. This can only be made possible if the toxic pollutants are removed or stabilized in the raw sediment and then fed back into the materials cycle. Currently, we are developing a pyrolysis process for the commercial-scale cleanup of dioxins and heavy metal-contaminated river sediment to yield reusable char for various economical applications. In this connection, this paper describes our preliminary investigation into the extent of dioxins and heavy metal volatilization from actual contaminated sediment. The stabilization of certain metallic species, particularly Cr ions, was studied. METHODS: Laboratory scale pyrolysis experiments were conducted using a special, horizontal lab-scale pyrolyzer. Sediment samples from Shanghai Suzhou Creek and Tagonoura harbor were pyrolyzed in the reactor under nitrogen gas at 800 degrees C and different retention times of 30, 60 and 90 min. A constant heating rate of 10 degrees C min(-1) was employed. The pyrolysis gas was first allowed to pass through a cold trap to condense the tar. Uncondensed gases were then channeled through a column containing an adsorbent (XAD-2 Resin) for dioxins. Heavy metal concentrations in the initial and final sediment residues were analyzed by ICP (Nippon Jarrel-Ash) following their acid and alkali (for Cr6+) digestion. Dioxin contents of the pyrolysis char, tar, and exhaust gases in the dioxin adsorbent were also determined. For comparative purpose, thermal treatment under air flow was conducted. RESULTS: The data for the removal of heavy metals from Suzhou Creek sediment showed very significant reductions in Pb, Zn and Cr6+ content of the sediment at this condition. Percentage removals were 42.4%, 60.8% and 42.2%, respectively. The disappearance of Cr6+ was due to reduction reactions rather than volatilization, since the total Cr content remained almost unchanged. Other heavy metals such as Cu, Fe and Ni showed very minimal reductions. Nonetheless, Toxicity Characteristics Leaching Procedure (TCLP) tests confirmed that these residual heavy metals were rather stable in the pyrolysis char. Reduction of toxic Cr6+ at 42.2% has also been achieved by pyrolysis (with N2) as opposed to the more than 580% increase in Cr6+ observed during thermal oxidation (with air). DISCUSSION: Pyrolysis also removes toxic organics, particularly dioxins, from the sediment. For the total dioxins, removal percentage of 99.9999% was achieved even at the lowest retention time of 30 min. Almost all polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzo-furans (PCDFs) were removed at any retention time. The TEQs detected from the solid residues were mainly contributed by dioxin-like PCBs, yet these were present in relatively trace quantities. At the shortest retention time of 30 min, only 0.000085 pg-TEQ g(-1) of polychlorinated biphenyls (PCBs) was detected in the pyrolysis char. Furthermore, the residual PCBs have very low toxicity ratings and none of the highly toxic PCBs, which were initially present in the sediment such as 3,3',4,4',5-PeCB and 3,3',4,4'5,5'-HxCB, were detected in the char. Results further confirmed that most of the dioxins that were removed were transferred to the gas phase so that volatilization may be considered as the main mechanism for their removal. CONCLUSION: Some heavy metals, particularly Pb and Zn, can be volatilized under N2 pyrolysis at 800 degrees C. Pyrolysis also prevented the formation of more toxic Cr6+ ions and, at the same time, resulted in its reduction by around 42.2%, in contrast to the 580% increase during thermal oxidation. PCDDs and PCDFs have been removed and were not formed in the solid products over the retention time range of 30-90 min at 800 degrees C. Dioxin-like PCBs mostly remained and a retention time of 30 min was found to be sufficient for its maximum removal. Recommendations and Perspectives. With the above results, a temperature of 800 degrees C at a retention time of 30 min is sufficient for the removal of total dioxins and of some heavy metals by volatilization. It is, however, necessary to destroy the dioxins as well as recover heavy metals in the gas phase. Stability of remaining heavy metals in the char also needs to be confirmed by leaching tests. These are the major concerns, which we are currently evaluating in order to establish the feasibility of our proposed, large scale pyrolysis system for sediment treatment.

Comparison of Vibrio harveyi strains isolated from shrimp farms and from culture collection in terms of toxicity and antibiotic resistance.

Vibrio harveyi strains isolated from shrimp farms (wild strains) were compared with those from culture collections in terms of minimum inhibitory concentration (MIC) and toxicity. Wild strains had higher MIC values for four antibiotics (kanamycin, carbenicillin, oxytetracycline and ampicillin) and also showed higher toxicity compared with culture collection strains. Vibrio harveyi with the lowest antibacterial resistance was chosen to test if a gradual increase in antibiotic concentration and frequent subculture would enhance its antibiotic resistance. Results showed that V. harveyi was able to develop resistance to oxytetracycline. The MIC value was 250 times higher compared with the MIC before subculturing. Moreover, the V. harveyi strain developed slightly higher toxicity. Therefore, it is possible that there is a relationship between antibiotic resistance and toxicity in V. harveyi.

Comparative analysis of bacterial diversity in freshwater sediment of a shallow eutrophic lake by molecular and improved cultivation-based techniques.

Comparative analysis of bacterial diversity in freshwater sediment collected from a shallow eutrophic lake was performed by using 16S rRNA gene clone library and improved cultivation-based techniques. Our study demonstrated that the use of gellan gum as a gelling reagent instead of agar was more effective at increasing culturability, cultivating a diverse array of novel microbes, and reducing the gaps of the results between molecular and cultivation-based analyses.

Detection of telomerase activity in tissues and primary cultured lymphoid cells of Penaeus japonicus.

Telomerase is a ribonucleoprotein enzyme that can elongate telomeric DNA, which is thought to be required for the development of cellular immortality and oncogenesis in mammals. We examined telomerase activity in tissues and primary cultured lymphoid cells of adult penaeid shrimps. Using the telomeric repeat amplification protocol (TRAP), we studied the characteristics of a putative novel telomerase in Penaeus japonicus. This telomerase could be inactivated by heating or treatment with RNase A or proteinase K. At elongation, this telomerase required dATP, dGTP, and dTTP, but not dCTP, as substrates. Sequence analysis of the TRAP product revealed that this telomerase synthesized (TTAGG)(n) repeated sequences. The activity of this telomerase was decreased but still readily detectable in 100 ng of protein extract from lymphoid tissue. The telomerase activity was detected in all examined tissues including testis, ovary, lymphoid, heart, hepatopancreas, and muscle. The highest telomerase activity was in the extract of ovarian tissues. In primary cultured lymphoid cells, the telomerase activity was retained. Thus, primary cultured lymphoid cells of Penaeus japonicus possess one of the factors necessary for cell line establishment.

Flavobacterium limicola sp. nov., a psychrophilic, organic-polymer-degrading bacterium isolated from freshwater sediments.

Three novel strains of cold-adapted bacteria, ST-82T, ST-10 and ST-92, were isolated from freshwater sediments. These three isolates were very similar to each other in phenotypic and chemotaxonomic traits, as well as in 16S rDNA sequence. The strains were Gram-negative, elongated filament-like rods that formed bright yellow colonies. They showed neither flexirubin pigments nor gliding motility. The strains were able to hydrolyse casein, gelatin, starch, agar, aesculin, urea, uric acid and tyrosine. They also lysed cells of Escherichia coil and Pseudomonas putida. The temperature range for growth was 0-25 degrees C, with optimum growth occurring at 15-20 degrees C. For all isolates, protease secretion increased as temperature decreased. Sodium chloride inhibited their growth, although the strains tolerated up to 1.5% (w/v) NaCl. Menaquinone-6 was the major respiratory quinone. The major cellular fatty acids were C15 : 0, iso-C15 : 0, anteiso-C15 : 0, C15:1, iso-C15:1, C16 : 1omega7cis, iso-C16 : 1, iso-C17 : 1, iso-C15 : 3-OH and iso-C16 : 0 3-OH. The DNA G + C content was 34.0-34.8 mol%. Phylogenetic analysis based on 16S rDNA sequences suggested that the strains belonged to the genus Flavobacterium and were closely related to Flavobacterium xanthum and Flavobacterium frigidarium, with sequence similarities of 96.9 and 96.3%, respectively. In physiological and biochemical analyses, the isolates were differentiated from all known members of the genus Flavobacterium. The name Flavobacterium limicola is proposed for these novel strains, and the type strain is ST-82T (=JCM 11473T =DSM 15094T).

Penaeid (Penaeus japonicus) lymphoid cells replicate by cell division in vitro.

Penaeid cell culture has gained much attention as a potential model to facilitate researches on the characterization of the virus and to develop more sophisticated and improved diagnostic procedures for use in the aquaculture industry. However, to date, cell division processes of cultured penaeid cells have not been found, which is suggested as one of the reasons that block the establishment of the continuous penaeid cell lines. We reported here the cell division processes of cultured lymphoid cells of Penaeus japonicus. The culture medium used was based on M199 and was modified by supplementing saline components. Cultures were incubated at 25 degrees C, and 5% CO2 was supplemented. In primary cultured lymphoid cells, dividing cells in different shapes were found. Cell division processes of 12 dividing lymphoid cells were tracked. After cell division, their daughter cells turned into fibroblast-like or epithelioid cells. These results proved that the culture conditions used were suitable for lymphoid cells of I japonicus to proliferate in vitro and that cultured lymphoid cells still had the ability to carry out cell division. These findings would give light to the establishment of continuous penaeid cell lines and would also provide us with the knowledge of cell division processes of the penaeid.