Activity of the fungus Pleurotus ostreatus and of its proteases on Panagrellus sp. larvae

Biological control has been shown to be one of the possible biotechnological applications of fungi and their proteases. The objective of this study was to evaluate the nematicidal activity of the fungus Pleurotus ostreatus and its proteases on Panagrellus sp. larvae. Proteolytic activity of P. ostreatus (PLO 06) was measured and characterized at different pHs, temperatures and in the presence of a inhibitor (PMSF). Daily samples of culture medium were collected in order to determine the period of maximum enzyme production. A zymogram showed the profile of several proteases. Predatory activity of the fungus P. ostreatus (PLO 06) was evaluated on Panagrellus sp. larvae (assay A) as well as the nematicidal activity of PLO 06 proteases on the same larvae (assay B). At pH 9 and 60°C, the activity of the proteases reached the maximum. In the presence of inhibitor, there was no proteolytic activity. A sample collected on the fifth day of incubation showed the highest enzyme activity. P. ostreatus demonstrated capture activity on larvae Panagrellus sp. The values of the reduction of the larvae (Assay A) were: day 1 (65.6%); day 2 (77.4%); day 3 (95.2%). The reduction of the larvae (Assay B) was 42%. P. ostreatus (PLO 06) and its proteases were very effective against Panagrellus sp. larvae, demonstrating great potential for use in integrated biological control.Keywords: Pleurotus, protease, Panagrellus sp., biological control, nematicidal. Abbreviation: PMSF, Phenylmethylsulfonyl fluoride

Nematicidal activity of Paecilomyces marquandii proteases on infective larvae of Ancylostoma spp

ABSTRACT The present study aimed to evaluate the action of Paecilomyces marquandii proteases on Ancylostoma spp L3. White halos in the zymogram confirmed the proteolytic action. Difference (p <0.01) between the number of L3 in the differents groups was found, with 41.4% of reduction of Ancylostoma spp. L3 before 24 hours

Population density, water supply, and the risk of dengue fever in Vietnam: cohort study and spatial analysis.

BACKGROUND: Aedes aegypti, the major vector of dengue viruses, often breeds in water storage containers used by households without tap water supply, and occurs in high numbers even in dense urban areas. We analysed the interaction between human population density and lack of tap water as a cause of dengue fever outbreaks with the aim of identifying geographic areas at highest risk. METHODS AND FINDINGS: We conducted an individual-level cohort study in a population of 75,000 geo-referenced households in Vietnam over the course of two epidemics, on the basis of dengue hospital admissions (n = 3,013). We applied space-time scan statistics and mathematical models to confirm the findings. We identified a surprisingly narrow range of critical human population densities between around 3,000 to 7,000 people/km² prone to dengue outbreaks. In the study area, this population density was typical of villages and some peri-urban areas. Scan statistics showed that areas with a high population density or adequate water supply did not experience severe outbreaks. The risk of dengue was higher in rural than in urban areas, largely explained by lack of piped water supply, and in human population densities more often falling within the critical range. Mathematical modeling suggests that simple assumptions regarding area-level vector/host ratios may explain the occurrence of outbreaks. CONCLUSIONS: Rural areas may contribute at least as much to the dissemination of dengue fever as cities. Improving water supply and vector control in areas with a human population density critical for dengue transmission could increase the efficiency of control efforts. Please see later in the article for the Editors' Summary