Functional assessment of subtilosin A against <em>Aeromonas</em> spp. causing gastroenteritis and hemorrhagic septicaemia

Abstract

Anti-<em>Aeromonas</em> and cell membrane lytic bacteriocin substance, subtilosin A producing <em>Bacillus subtilis</em> VT03 was explored. Strain VT03 was isolated from freshwater fish (<em>Tilapia</em>) intestine and screened for its antimicrobial activity against four pathogenic strains of <em>Aeromonas</em> 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 <em>Bacillus subtilis</em> using 16S rRNA sequencing. Cell free supernatant (CFS) of the strain VT03 was active against pathogenic strains of <em>Aeromonas</em> spp, subsequently CFS was partially purified and designated as PPB-VT03 showing inhibition against <em>A. hydrophila</em> 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 (<em>sboA</em>) was found to be present whereas subtilin (<em>spaS</em>) 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 <em>Bacillus subtilis</em> as a potent source for antibacterial peptide.