The Culicidae are biting insects that are most harmful to people. They are almost all blood-suckers, and are responsible for the spread of many important diseases such as malaria, yellow fever and elephantiasis. Entomopathogenic microorganisms occupy an important place among the alternative methods of fighting against pests insect. The fungus, Beauveria bassiana is an entomopathogenic agent naturally present in the ecosystems and offers a very interesting potential for controlling populations of mosquitoes. Our study aims at showing the 4 th stage larvae histological changes of the domestic mosquito Culex pipiens, treated with the entomopathogenic fungus B. bassiana in suspension which corresponds to a dose of 10 7 spore/mL. In fact, after developing the individuals in the fungal solution, histological study was carried out on the following parts; cuticle, intestine, adipose tissue and hemolymph. The histological studies showed many alterations and malformation in the treated 4 th instar larvae body and tissues. The infection affected the different parts of the body, especially the cuticle, the adipose cells, and midgut, in addition to the development and the colonization of B. bassiana inside tissues. The application of B. bassiana on the cuticle of the larvae was dependent on an apparent disturbance in the structure of the cuticle or the degeneration of its different parts. The fungus infection does not stop at the level of the body walls, so it even goes to adipose tissue, epidermal cells and intestine. Based on these results, B. bassiana could be suggested as suitable biocontrol agent against C. pipiens.
SUMMARYFew years ago, considerable progress has been made to explain the disappearance of bee colonies, including correct identification of pests involved and the search for more effective and healthy alternatives to protect them. Indeed, our work is based on the isolation, characterization and identification of entomopathogenic bacterial strains of the genus Bacillus from larvae of wax moth Galleria mellonela reared in the laboratory, with a preliminary study of the use of these entomopathogenic bacteria on the larvae (L5) of G. mellonella under controlled conditions. In fact, 9 bacterial strains of the genus Bacillus have been isolated. They are spore forming bacteria, Gram, catalase and oxidase positive and present variable responses to the gelatinase test, lecitinase, caseinase, culture in anaerobiosis and growth at different temperatures (45 ° C., 55 ° C., 65 ° C.). From our study, we also find that the strain S4, probably identified as Bacillus thuringiensis, has a better effect on the larvae of Galleria mellonella. It caused very remarkable symptoms and mortality rates that vary depending on the strain and bacterial concentration tested and the mode of application. Injection of strain S4 for individuals resulted mortality of 83.33%, 75% and 50%, respectively, after treatment with high, medium and low concentration after only 3 days. The comparative examination of the hemolymph test results shows that the injection of the bacteria into the larvae resulted in a significant increase in hemolymph protein and carbohydrate content as compared to controls.
Varroa destructor is an obligatory ectoparasite of the honeybee (Apis mellifera L). The mites use their piercing month parts to suck out hemolymph from immature and adult bees caused direct damage (morphological, physiological abnormalities) and indirect damage due to microbial pathogens. The aim of this work was to research the bacterial microflora in hemolymph of emerging healthy and parasitized worker honeybee by Varroa destructor. For the isolation and identification of the bacteria, the morphological and biochemical tests were done. The results showed that the haemolymph of the healthy worker (Apis mellifera L) is free of bacteria. When the V.destructor breaks the cuticle, the microorganisms invade the heamolymph. The infested worker honeybees harbored a total 9 strains belonging to 6 strains of Bacillacea (66,66%), 1 of Peanibacillacea (11,11%) and 2 of Enterobacteriacea (22,22%). Based on the Gallery API 20 E (Bio-Merieux), the genera of Bacillacea and Peanibacillacea included Bacillus licheniformis (4 strain), Bacillus mycoide (1strain), Bacillus coagulans (1 strain) and Brevibacillus chohinensis (1 strain) respectively. Bacillus licheniformis was for probably the most frequent species. The Enterobacteriaceae included Aeromonas hydrophila and Pantoa sp.
The use of bacteria in the control of insect pests is a form of biological control whose practice is still not widespread. It is in this context that the present work falls. It concerns the isolation, characterization and identification of local bacterial strains for the purpose of their use in the control of certain pests. Indeed, 20 bacteria were isolated from soil cultivated in the region of Boumerdes (center of Algeria) with a total of 21 bacterial strains isolated from Adrar region (Desert Algerian). After carrying out the efficacy tests against 2 insect pests; Migratory locust (Locusta migratoria) and wax moth (Galleria mellonella), 8 potentially interesting strains were identified based on their genetic traits. Molecular characterization of these strains was performed by isolation of DNA, PCR and sequencing of the 16S rRNA gene, followed by phylogenetic analysis. The rDNA16S sequences of the 8 strains named B1, B2, B3, B4, B5, B6, H1 and H2 were recorded in the EMBL/EBI database and their phylogenetic analysis revealed that they belong to the genera Bacillus, Pseudomonas, Enterobacter and Delftia with a very high percentage of similarity with Bacillus thuringiensis strains (NR_043403) (99%) for isolate B1, Bacillus weihenstephanensis (NR_024697) (99%) for isolate B2, Pseudomonas fragi (JCM5420) (99%) for isolates B3 and B4, Bacillus thuringiensis (CMBLBT-5) (99%) for isolate B4, Enterobacter ludwigii (EN-119) for B5, Bacillus thuringiensis (4916) (99%) for isolate H1 and Delftia lacustris (R-54734) (100%) for isolate H2.
Entomopathogenic microorganisms occupy an important place among the alternative methods of fighting against pests insect. The fungus Beauveria bassiana is an agent naturally present in ecosystems. It has potential to control pest populations. In the context of biological control, the present work aims to the study of linear growth of Beauveria bassiana on different natural environments from the food industry. They are the raw whey, water and pomace, and followed the development of the fungus through a trial production of biomass on deproteinized whey.
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