Larvicidal activity of microbial metabolites extracted from extremophiles against vector mosquitoes

Authors: Bela M Nabar, Swapnil Lokegaonkar

A Mosquitoes transmit disease agents which are responsible for more than 500 million clinical cases estimated by the World Health Organization. The increase in number of resistant varieties of mosquitoes, ineffectiveness of chemical insecticides, necessitates the development of vector control strategies. Thus microbial insecticides can be considered as alternatives to chemical insecticides. In Present study soil and water samples from biodiverse natural habitats such as cold regions and hot water springs were collected and used for screening of bacteria. The extracellular secondary metabolites from the isolates were extracted and tested for its mosquito larvicidal activity against fourth instar larvae of Culex and Aedes mosquito larvae.
Total 86 soil and water samples were collected from hot water springs, and extremely cold regions of India. 124 bacterial isolates comprising of 24 psychrophiles, 38 mesophiles and 62 thermophiles were obtained. Mosquito larvicidal activity was rendered by 21 isolates and was found to be effective in control of the mosquito larvae. The secondary metabolites were evaluated for its toxicity and the percentage mortality against the larvae was determined. 25% of secondary metabolites showed 100 % mortality against Culex at 200 ppm, while 50% of the secondary metabolites showed mortality at 400ppm against Aedes larvae. The LC50 of the extracted secondary metabolites of the thermophilic isolates was found to be significantly low, about 150ppm. Further efficient thermophilic bacteria were identified biochemically and belonging to Bacillus and Corynebacterium genera.

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