Abstract

A PRELIMINARY STUDY ON MOSQUITOCIDAL ACTIVITY AND EXTRACELLULAR PROTEASE PRODUCTION BY BACTERIAL ISOLATES FROM SOIL

Sumitha J.* and Akila M. P.

Abstract

The insects have traditionally been fought with chemical pesticides with their disadvantages like long term toxicity, environmental pollution and food chain accumulation. Their lethal effects also fairly nonspecific are killing beneficial predators that naturally control the pest population. Bio-insecticides were formulated to overcome the disadvantages of chemical pesticides. Biological control is one of the main components of IPM (Indian Pest Management) and there has been greater awareness to utilize the insect pathogens in IPM systems in recent years. Though commercial formulations are not used widely at present in India, studies carried out in various parts of our country reveal their potential use. But both in bacterial isolates from soil and in their mosquitocidal activity not too many studies have been carried out and there is a need to take up systematic surveys to identify naturally occurring insects’ pathogens under varied agro-ecological conditions. Proteolytic enzymes are ubiquitous in microorganisms and the extracellular proteases are probably the most widespread of all microbial secreted enzymes. These enzymes are simple to detect and are often synthesized in high yield. They have therefore been extensively studied and their molecular properties are understood in detail. Microbial proteases are produced from high yielding strains by fermentations under controlled conditions in surface or submerged culture. The enzymes are produced extracellularly and recovery involves separation of the cell free liquor by filtration or centrifugation. This study has tried to exploit the diverse potential of bacteria isolated from soil sample by studying its mosquitocidal activity by determining the LC50 and LC90 of the potential isolates against larva of Culex quinquefasciatus as well as studying the extracellular protease production by them. Out of 48 bacteria isolated from soil samples, only one showed remarkable larvicidal activity, marked as BII. And among 5 bacteria isolates tested for proteases production all showed pro-teases production with one species (BI) showing highest production.

Keywords: Proteases, Culex Quinquefasciatus, Mosquiticidal Property.