Functional assessment of subtilosin A against Aeromonas spp. causing gastroenteritis and hemorrhagic septicaemia

Anti-Aeromonas and cell membrane lytic bacteriocin substance, subtilosin A producing Bacillus subtilis VT03 was explored. Strain VT03 was isolated from freshwater fish (Tilapia) intestine and screened for its antimicrobial activity against four pathogenic strains of Aeromonas spp. causing gastroenteritis and hemorrhagic septicaemia. Isolate (VT03) was identified showing inhibition in agar spot assay. The strain VT03 was the one exhibiting strong inhibition and identified as Bacillus subtilis using 16S rRNA sequencing. Cell free supernatant (CFS) of the strain VT03 was active against pathogenic strains of Aeromonas spp, subsequently CFS was partially purified and designated as PPB-VT03 showing inhibition against A. hydrophila ATCC 49140. PPB-VT03 completely lost its activity upon treating with proteinase K revealing that the defense molecule could be proteinaceous in nature. Based on polymerase chain reaction (PCR), functional gene coding for subtilosin A (sboA) was found to be present whereas subtilin (spaS) was absent. The role of partially purified bacteriocin of isolate VT03 (PPB-VT03) through FTIR and SEM analysis revealed the activity of cell lysis. The study demonstrated the potential use of subtilosin A producing Bacillus subtilis as a potent source for antibacterial peptide.