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 198 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 30 °C for 24-48 h. The isolates were tested for their antagonistic activity in contact with Vibrio harveyi. Two strains (IS02 and IS03) that isolated from the gut and pond sediment were showed antagonistic against V. harveyi. According to 16S ribosomal DNA gene sequence analysis, the strain IS02 was identified as Bacillus subtilis and IS03 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 IS02 and B.vallismortis IS03 had biocontrol activity against V. harveyiin vitro and in vivo and they increase growth performance of L.vannamei in post larvae stage.