Hemolysin, Protease, and EPS Producing PathogenicAeromonas hydrophilaStrain An4 Shows Antibacterial Activity against Marine Bacterial Fish Pathogens

Abstract

A pathogenicAeromonas hydrophilastrain An4 was isolated from marine catfish and characterized with reference to its proteolytic and hemolytic activity along with SDS-PAGE profile (sodium dodecyl sulphate-Polyacrylamide gel electrophoresis) of ECPs (extracellular proteins) showing hemolysin (approximately 50 kDa). Agar well diffusion assay using crude cell extract of the bacterial isolate clearly demonstrated antibacterial activity against indicator pathogenic bacteria,Staphylococcus arlettaestrain An1,Acinetobactersp. strain An2,Vibrio parahaemolyticusstrain An3, andAlteromonas aurentiaSE3 showing inhibitory zone >10 mm well comparable to common antibiotics. Further GC-MS analysis of crude cell extract revealed several metabolites, namely, phenolics, pyrrolo-pyrazines, pyrrolo-pyridine, and butylated hydroxytoluene (well-known antimicrobials). Characterization of EPS using FTIR indicated presence of several protein-related amine and amide groups along with peaks corresponding to carboxylic and phenyl rings which may be attributed to its virulent and antibacterial properties, respectively. Besides hemolysin, EPS, and protease,Aeromonas hydrophilastrain An4 also produced several antibacterial metabolites.