Bacillus altitudinis: a sustainable mosquito controlling biopesticide isolated from the rhizospheric soil of Nypa fruticans in mangrove forest.

BACKGROUND

Mosquitoes are ancient enemies of humans and act as vectors of many life-threatening diseases, including dengue, malaria, chikungunya, filariasis. In Bangladesh, more than a hundred thousand individuals suffered from dengue in 2019 and this number is increasing consistently at every year. For sustainable control of mosquitoes, we aimed to isolate and characterize mosquito controlling Bacillus species from mangrove forests and municipal areas in Bangladesh.

RESULTS

Initially, 38 bacteria were isolated in laboratory via the heat-shock method and categorized by morphological studies, Gram staining, and catalase test. To conduct different in vitro and in vivo trials, 16S rRNA gene sequencing-based molecular prediction of 12 bacterial strains was conducted via amplification with 27 F and 1492R universal primer pairs. Antimicrobial assays, salt and pH tolerance tests, amylase, cellulase, protease, and antibiotic susceptibility test were performed on Bacillus sp. to identify their multiplication potential in diverse and challenging environments. However, larvicidal assay was conducted against Aedes (Aedes aegypti) and Culex (Culex quinquefasciatus) mosquitoes to select the best potential biopesticide among the 6 selected Bacillus species (Bacillus tropicus, Bacillus thuringiensis, Bacillus zanthoxyli, Bacillus altitudinis, Bacillus pseudoflexus, and Fictibacillus barbaricus), and a lethality test was conducted for four potential biopesticides, all of which showed no lethality to Artemia salina in aquatic environment. The whole genome sequence (WGS) data obtained with the "K-mar" finder revealed that the best biopesticide bacteria was Bacillus altitudinis.

CONCLUSIONS

To the best of our knowledge, this is the first report that Bacillus altitudinis has mosquito larvicidal activity and can be a commercial and ecofriendly mosquito controlling biopesticides after scaling up.