Application of Bacillus spp. Isolated from the Intestine of Black Tiger Shrimp (Penaeus monodon Fabricius) from Natural Habitat for Control Pathogenic Bacteria in Aquaculture

Abstract

Bacillus spp. were isolated from the intestine of black tiger shrimp Penaeus monodon which were collected from the Gulf of Thailand at Chonburi province area during October 2005 to September 2006. The bacterial antagonist activity were tested with aquacultural pathogenic bacteria. The cross streak method results showed that Bacillus W803 and Bacillus W120 could inhibit Aeromonas hydrophila AQAH after 24 hours. The highest level of antibacterial substances of these Bacillus were found in 48 hours. However, Bacillus W120 could produce antibacterial substances higher than Bacillus W803. Bacillus W806 and Bacillus W902 could colonize Streptococcus agalactiae AQST after 48 hours of incubation. Although cross streak method did not show any effect between Bacillus spp. and Vibrio harveyi AQVH, but Transmission Electron Microscope (TEM) observations showed the size of V. harveyi cell at cross streaking point with Bacillus WL01 to be smaller compared to normal cell with width and length reduction of 58.54% and 72.07%, respectively. Application of these selected Bacillus strains to use for control the pathogenic bacteria were conducted. The amount of A. hydrophila AQAH co-cultured in sterile tap water with Bacillus W803 and Bacillus W120 were decreased by 22.42 and 27.05%,
respectively. The amount of S. agalactiae AQST co-cultured in sterile tap water with Bacillus W806 and Bacillus W902 were decreased by 11.98 and 11.97%, respectively. The amount of V. harveyi AQVH co-cultured in sterile artificial sea water (20 ppt) with Bacillus WL01 and Bacillus W1106 were decreased by 22.75 and 20.23%, respectively. Moreover, Bacillus spp. could survive in water more than 5 days and could decrease pathogenic bacteria from 10⁶ to 10⁵ CFU/ml in 24-48 hours. These results suggest that these Bacillus spp. can be applied as effective probiotic to control pathogenic bacteria in aquaculture.