Screening and evaluation of indigenous bacteria from the Persian Gulf as a probiotic and biocontrol agent against Vibrio harveyi in Litopenaeus vannamei post larvae

Isolation of autochthonous bacteria from marine sources as a potential probiont in biocontroling against pathogenic Vibrio species in the shrimp culture industry was the aim of current research. A total of ۱۹۸ bacterial strains were isolated from pond water, sediment, hepatopancreas and gut samples of shrimps after culturing the samples on Tryptic Soy Agar and incubated at ۳۰ °C for ۲۴-۴۸ h. The isolates were tested for their antagonistic activity in contact with Vibrio harveyi. Two strains (IS۰۲ and IS۰۳) that isolated from the gut and pond sediment were showed antagonistic against V. harveyi. According to ۱۶S ribosomal DNA gene sequence analysis, the strain IS۰۲ was identified as Bacillus subtilis and IS۰۳ as B.vallismortis. Further, the two bacterial species, B. subtilis and B. vallismortis were challenged separately for probiotic activity in the post larvae of Litopenaeusvannamei against pathogenic V. harveyi. The present study identified B.subtilis IS۰۲ and B.vallismortis IS۰۳ had biocontrol activity against V. harveyiin vitro and in vivo and they increase growth performance of L.vannamei in post larvae stage.