<i style="">In vitro</i> and <i>in</i><i style=""> vivo</i> biocontrol of <i style="">Vibrio harveyi</i> using indigenous bacterium, <i style="">Bacillus </i>spp.

Abstract

The present study was undertaken to find out the potential of indigenously isolated <i>Bacillus</i> spp. in controlling virulent luminous <i>Vibrio</i> <i>harveyi</i> infection in shrimp <i>in</i> <i>vitro</i> and <i>in</i> <i>vivo.</i> Luminescent bacteria<i> </i>were isolated from shrimp farms of east coast of India. It is biochemically and genetically identified as <i>Vibrio</i> <i>harveyi</i>. Two isolates of <i style="">Vibrio</i> <i style="">harveyi</i> obtained from infected shrimps were used for pathogenicity studies in juvenile shrimps and the LD50 values for the above isolates ranged between 3.7 x 10⁶to 8.9 x 10⁷ CFU/ml. Indigenously isolated and identified <i>Bacillus</i> spp. exhibiting antagonism were used for controlling the <i>Vibrio</i> infection both <i style="">in vivo</i> and <i style="">in vitro</i>. <i>In vivo</i> antagonistic activity was studied with three selected <i>Bacillus </i>isolates. The same had reduced the mortality of <i>Penaeus monodon</i> juveniles when challenged with <i>V</i>. <i>harveyi</i> with an RPS of 87.5 - 50%. This is without affecting the multiplication of the pathogen in water. Present study found that indigenously isolated antagonistic <i>Bacillus </i>sp. could be used as effective biocontrol agents against pathogenic luminescent <i>V</i>. <i>harveyi</i>.