The complete genome sequence of Clostridium botulinum F str. 230613, insertion sites, and recombination of BoNT gene clusters.

The genomic DNA of Clostridium botulinum F str. 230613 includes a chromosome (3 993 083 bp, 3502 coding sequences (CDs)) and a plasmid (17 531 bp, 25 CDs). The arrangement of the botulinum neurotoxin serotype F (BoNT/F) gene cluster, a 15-kb (or longer) fragment including the bont gene and other relevant genes, and its different insertion sites in C. botulinum A2 and C. botulinum F were formulated. Mobile elements and virulence factors were analysed. We also found a cell adhesion and pectin lyase domain-containing protein, which may function in attaching to the host and as a pectin lyase. The nine BoNT gene clusters of group I C. botulinum strains were located at three sites in the chromosome of C. botulinum F str. 230613. This study showed the inserting inclination of BoNT/A1 tend to have gene clusters inserted at site 3, BoNT/F at site 2, and BoNT/A2 at site 1. Additionally, we found the recombination event between the BoNT gene clusters of sites 2 and 3, a mechanism that contributed to the diversity of the BoNT gene cluster arrangement.

Shiga toxin type 2 (Stx2), a potential agent of bioterrorism, has a short distribution and a long elimination half-life, and induces kidney and thymus lesions in rats.

Shiga toxin type 2, a major virulence factor produced by the Shiga toxin-producing Escherichia coli, is a potential toxin agent of bioterrorism. In this study, iodine-125 (125I) was used as an indicator to describe the in vivo Stx2 biodistribution profile. The rats were injected intravenously (i.v.) with 125I-Stx2 at three doses of 5.1-127.5 µg/kg body weight. Stx2 had a short distribution half-life (t (1/2)α, less than 6 min) and a long elimination half-life in rat. The toxicokinetics of Stx2 in rats was dose dependent and nonlinear. Stx2 concentrations in various tissues were detected at 5-min, 0.5-h, and 72-h postinjection. High radioactivity was found in the lungs, kidneys, nasal turbinates, and sometimes in the eyes, which has never been reported in previous studies. In a preliminary assessment, lesions were found in the kidney and thymus.

Passive protection of purified yolk immunoglobulin administered against Shiga toxin 1 in mouse models.

Shiga toxins produced by Escherichia coli O157:H7 cause a wide spectrum of enteric diseases, such as lethal hemorrhagic colitis and hemolytic uremic syndrome. In this study, the B subunit protein of Shiga toxin type 1 (Stx1) was produced in the E. coli system, was further purified by Ni-column Affinity Chromatography method, and was then used as an immunogen to immunize laying hens for yolk immunoglobulin (IgY) production. Titers of IgY increased gradually with boosting vaccination and, finally, reached a level of 105, remaining steady over 1 year. Then the protective efficacy of IgY against Stx1 was evaluated by in vitro and in vivo experiments. It was shown that the anti-Stx1 IgY could effectively block the binding of Stx1 to the Hela cells and could protect BALB/c mice from toxin challenges. The data indicates the facility of using egg yolk IgY as a therapeutic intervention in cases of Shiga toxin intoxication.

[Kinetics on dimethoate aqueous solution degradation in ultrasonic airlift loop Reactor].

The kinetic rules of degradation were studied in ultrasonic airlift loop reactor (UALR) in which O3 was introduced as oxidant and the organophosphorus pesticide dimethoate was used as typical contaminant. It was found that the dimethoate degradations under the individual ultrasonic radiation treatment without O3 (US), the oxidation of O3 gas (O3) and the synergetic effect of UALR and O3 (UALR/O3) were all consonant with the apparent first-order reaction by the kinetics investigations. The dimethoate removal rates of US, O3 and UALR/O3 methodologies under the conditions of dimethoate initial concentration of 50 mg/L, initial solution pH of 6.0, dimethoate solution volume of 80 mL, ultrasonic intensity of 0.5 W/cm2, O3 flow of 200 L/h, temperature of 20 degrees C and the treatment time of 4 h were 27%, 15% and 90%, respectively. Under these conditions, the rate constant enhancement factor of dimethoate degradation reached 4.816. Furthermore, a simplified mechanistic kinetic model was derived from the degradation mechanism of the synergetic effect of US, O3 and hydroxyl free radical (*OH) in the UALR/O3 system.

Study on degradation of dimethoate solution in ultrasonic airlift loop reactor.

In this work, the degradation of dimethoate solution in ultrasonic airlift loop reactor (UALR) assisted with advanced oxidation processes was studied. The effects of O3 flow rate, ultrasonic intensity, pH value and reaction temperature on the degradation rate were investigated. UALR imposed a synergistic effect combining sonochemical merit with high O3 transfer rate. Under the optimal operation conditions: ultrasonic irradiation time was 4h, O3 flow rate was 0.41 m3h(-1), ultrasonic intensity was 4.64 W cm(-2), pH value was 10.0, reaction temperature was 25 degrees C, and initial concentration of dimethoate was 20 mg L(-1), degradation rate of dimethoate increased to 90.8%. The experimental results indicated that the method of UALR degradation of organic pollutants in the presence of gas could reduce reaction time and improve degradation rate. UALR was an advisable choice for treating organic waste waters and this device could be easily scale up. Thus this process has wide application prospect in industry.