A comprehensive study of novel extremophilic soil bacterial isolates from Sundarbans mangrove sediments as a biocontrol agent for mosquito vector management.

BACKGROUND

Mosquitoes are significant vectors of infectious diseases posing considerable public health risks. Despite practice of extensive use of synthetic insecticides to control vectors, their efficacy has declined due to widespread resistance which underscores urgent need for alternative approaches like entomopathogenic bacteria. This study was aimed to isolate and evaluate salt-tolerant insecticidal soil-dwelling bacteria targeting the salt-tolerant larvae of Aedes albopictus, Culex quinquefasciatus and Anopheles stephensi.

RESULTS

Marine soil samples collected from Digha and the Sundarbans, India, were analyzed, leading to the isolation of three bacterial strains: Halobacillus marinus MB201, Bacillus paralicheniformis BB105 and Priestia aryabhattai SNC510. Among these, H. marinus MB201 exhibited the highest larvicidal activity with median lethal concentration (LC) values of 1.87, 2.71 and 3.68 mg/L against Ae. albopictus, Cx. quinquefasciatus and An. stephensi larvae, respectively. Scanning and transmission electron microscopy confirmed that H. marinus MB201 is rod-shaped and Gram positive. Liquid chromatography-mass spectrometry (LC-MS) analysis identified key larvicidal toxins, including nigakilactone F, nicotine and batrachotoxin, which acts as a sodium channel modulator responsible for larval paralysis and mortality. Molecular docking studies corroborated these findings which validated H. marinus MB201 as a promising biolarvicide. Whole-genome transcriptomic profiling of H. marinus MB201 (GenBank accession number PQ496007) revealed significant transcriptional changes under saline stress including up-regulation of 781 genes and down-regulation of 942 genes that highlight adaptations for osmoregulation, ion transport and osmoprotectant synthesis.

CONCLUSION

Importantly, non-pathogenicity tests confirmed its safety for humans and supports its potential for sustainable mosquito vector management in saline environments. This study underscores viability of the H. marinus MB201 as an eco-friendly solution for mosquito control in the context of climate change. © 2025 Society of Chemical Industry.