Exploitation of Endemic Extremophilic Microbial Strains Isolated from Date Palm Fibrillium in the Saoura Region (Southwest Algeria) as Potential Biocontrol Agents against Mosquitoes

Ali  Boulanouar; Larbi  Benlarbi; Zineb  Hamani

doi:10.18502/jad.v19i3.20895

Ali Boulanouar Laboratory of Biological Resources Valorization and Food Safety (BRVFS), Faculty of Natural and Life Sciences, Tahri Mohamed University of Bechar, Béchar, Algeria
Larbi Benlarbi Laboratory of Biological Resources Valorization and Food Safety (BRVFS), Faculty of Natural and Life Sciences, Tahri Mohamed University of Bechar, Béchar, Algeria
Zineb Hamani Laboratory of Biological Resources Valorization and Food Safety (BRVFS), Faculty of Natural and Life Sciences, Tahri Mohamed University of Bechar, Béchar, Algeria

DOI: https://doi.org/10.18502/jad.v19i3.20895

Keywords: Biological control; Chitinolytic microorganisms; Culex pipiens; Phoenix dactylifera

Abstract

Background: Algeria’s extreme ecosystems, such as the Saoura region, represent unique reservoirs of rare microorganisms, inhabiting pristine and unexplored virgin territories with considerable biotechnological potential. Chitinolytic bacteria are particularly noteworthy for mosquito control due to their ability to degrade chitin, the major structural component of the insect cuticle. This study aims to: (i) identify new microbial strains adapted to extreme desert conditions, overcoming the limited efficacy of some bioinsecticides, (ii) address the spread of vector-borne diseases and mosquito resistance, (iii) reduce the environmental impacts of non-selective insecticides, and (iv) explore eco-friendly strategies and integrated biological control.

Methods: Shrimp chitin was extracted to prepare selective media for the isolation and purification of chitinolytic bacteria. The entomopathogenic activity of these chitinolytic strains at concentrations of 10⁴, 10⁵ and 10⁶ CFU/mL was evaluated through bioassays on Culex pipiens larvae.

Results: We isolated three chitinolytic strains from Phoenix dactylifera bark, among which Streptomyces spp. 2 (STR2) was clearly the most virulent against Cx. pipiens larvae. This strain exhibited marked dose and time-dependent toxicity (LC₅₀-LC₉₉: 7.9×10³-3.4×10⁷ CFU/mL; DC: 6.8×10⁷ CFU/mL; LT₅₀: 4.6 days). Beyond larval mortality, it also severely affected adults by reducing the proportion of flight-capable mosquitoes and increasing rates of flightlessness, post-emergence mortality, and deformity. However, an IGR-like mode of action remains speculative.

Conclusion: This study confirms the larvicidal activity of desert-adapted chitinolytic bacteria, but further research is needed to determine their selectivity toward non-target organisms before considering their application in mosquito management.