Enhanced Mosquito Larvicidal Efficacy and Dehairing Properties of Bacillus thuringiensis Serovar israelensis Strain VCRC-B649 Isolated from Malabar Coast, India.

Abstract

In recent years, there has been a global threat from emerging vector-borne diseases (VBD), despite the implementation of several vector control programs. Considering the benefits of bacterial pesticides, the present study aimed to isolate potential mosquitocidal bacteria from the various soil types collected from the Kasaragod (12.5°N, 75.0°E) district of Kerala, India. One bacterial strain was isolated from the coastal alluvium soil and showed promising mosquitocidal activity. The mosquitocidal isolate was identified as Bacillus thuringiensis serovar israelensis strain VCRC-B649 through phylogenetic analysis of whole genome sequence. LC₅₀ values against Culex quinquefasciatus, Aedes aegypti, and Anopheles stephensi larvae were determined as 0.0064, 0.0072, and 0.0101 mg/L, and LC₉₀ values were 0.0127, 0.0140, and 0.019 mg/L. Comparative analysis of larvicidal activity of this strain has revealed more efficacy than the WHO reference strain of B. thuringiensis var. israelensis (H14) The cry and cyt gene profile of this isolate is found to be similar to WHO reference strain of B. thuringiensis var. israelensis (H14). This new isolate has not shown any adverse effects against aquatic non-target organisms. Further evaluation of its morphological, biochemical characteristics and growth kinetics revealed similarities with already reported B. thuringiensis strains. Sporulated culture at 72 h showed maximum (20.6 ± 1.5 mm) proteolytic activity and animal skin (goat skin) dehairing property and revealed the industrial applications of this new strain. This is the first report on the isolation of mosquitocidal bacterial strain with enzyme-producing property from the Malabar coastal region and it was proven to be a more suitable alternative biocontrol agent for controlling the disease transmitting mosquito vectors with translational value.