Environmental Fate of Two Organophosphorus Insecticides in Soil Microcosms under Mediterranean Conditions and Their Effect on Soil Microbial Communities

Assessing dissipation is an integral part of determining pesticide risk. The adsorption and dissipation characteristics of two model insecticides, chlorpyrifos (CHP) and dimethoate (DMT), in a Mediterranean soil were investigated in order to evaluate soil microbial toxicity and to study their soil bioavailability for the purpose of managing pesticide residue with potential bioremediation of contaminated soil. The aim of this study was also to define novel methods for assessing the ecotoxicity of CHP and DMT on microorganisms in the soil. Koc values ranged between 33420–91601 cm³/g and 129–184 cm³/g for CHP and DMT, respectively, indicating that the former is characterized by a strong adsorption affinity, whereas, the latter has a weaker one. In the dissipation study, the half-life (T_1/2) of CHP in top soil was 11.55days; whereas, when dissipation was studied in the same soil sterilized, the half-life was 13.86 days, showing a relatively important abiotic degradation effect. For DMT, however, T_1/2 was 17.32 days and 13.86 days in sterilized soil and non-sterilized soil, respectively, illustrating partial biotic degradation. In terms of leaching behavior, the groundwater ubiquity scores calculated for CHP and DMT were 0.85 and 1.95, respectively, indicating that CHP is a non-leacher, while DMT can be considered a transition insecticide.     

Modulation of Endotoxicity of Shigella Generalized Modules for Membrane Antigens (GMMA) by Genetic Lipid A Modifications: RELATIVE ACTIVATION OF TLR4 AND TLR2 PATHWAYS IN DIFFERENT MUTANTS*

Outer membrane particles from Gram-negative bacteria are attractive vaccine candidates as they present surface antigens in their natural context. We previously developed a high yield production process for genetically derived particles, called generalized modules for membrane antigens (GMMA), from Shigella. As GMMA are derived from the outer membrane, they contain immunostimulatory components, especially lipopolysaccharide (LPS). We examined ways of reducing their reactogenicity by modifying lipid A, the endotoxic part of LPS, through deletion of late acyltransferase genes, msbB or htrB, in GMMA-producing Shigella sonnei and Shigella flexneri strains. GMMA with resulting penta-acylated lipid A from the msbB mutants showed a 600-fold reduced ability, and GMMA from the S. sonnei ΔhtrB mutant showed a 60,000-fold reduced ability compared with GMMA with wild-type lipid A to stimulate human Toll-like receptor 4 (TLR4) in a reporter cell line. In human peripheral blood mononuclear cells, GMMA with penta-acylated lipid A showed a marked reduction in induction of inflammatory cytokines (S. sonnei ΔhtrB, 800-fold; ΔmsbB mutants, 300-fold). We found that the residual activity of these GMMA is largely due to non-lipid A-related TLR2 activation. In contrast, in the S. flexneri ΔhtrB mutant, a compensatory lipid A palmitoleoylation resulted in GMMA with hexa-acylated lipid A with ∼10-fold higher activity to stimulate peripheral blood mononuclear cells than GMMA with penta-acylated lipid A, mostly due to retained TLR4 activity. Thus, for use as vaccines, GMMA will likely require lipid A penta-acylation. The results identify the relative contributions of TLR4 and TLR2 activation by GMMA, which need to be taken into consideration for GMMA vaccine development.     

Effect of meta-Topolin on micropropagation and adventitious shoot regeneration in Prunus rootstocks

The effect of meta-Topolin (mT), an aromatic natural cytokinin, on micropropagation and adventitious shoot regeneration was evaluated on Prunus rootstocks, Torinel (Prunus domestica L.) and Ferdor (Prunus insititia  ×  domestica). In vitro shoots were grown for three subcultures on a multiplication medium containing 2.1, 4.2 or 6.3 μM of mT or 2.1 µM N ⁶-benzyladenine (BA). Then, apical leaves were excised and transferred on a medium supplied with BA, thidiazuron (TDZ) or zeatin for adventitious regeneration. Shoots multiplied on 2.1 μM mT or BA, were also induced to root with α-naphthalene acetic acid and acclimatized. meta-Topolin did not improve shoot proliferation, respect to BA, however, positively influences growth and quality of shoots. Ferdor from mT showed higher rooting percentage (92 %), root number and length, respect to the control, while a similar response was observed in Torinel with both cytokinins. Acclimatisation was higher than 90 % for both genotypes and, after 5 months, the highest length of roots was found in plants from mT. Adventitious regeneration was obtained only in leaves from shoots previously grown on mT. The highest regeneration responses, 65 and 42 %, respectively for Ferdor and Torinel, were obtained in the regeneration medium supplied with TDZ.