Antibacterial protein fraction derived from Streptomyces fradiae against septicemia infection in Labeorohita: Breakthrough in marine drug discovery

Abstract

The aquaculture sector continues to be an essential source of food, revenue, nutrition, and a means of subsistence for numerous people globally. Intensive aquaculture in a confined region induces environmental stress in farmed fish, which indirectly increases their vulnerability to many diseases. Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio harveyi are the causative bacterial pathogens for septicemia, the most prevalent and commonly seen illness. Disease outbreaks result in a rise in mortality or a decrease in the quality of the meat, consequently inflicting substantial economic losses to carp production. In contrast, the continual use of antibiotics for infection management has contributed to the proliferation of drug-resistant bacteria in aquatic environments. In this context, marine actinobacteria are emerging as possible sources of new secondary metabolites to combat the problem. Actinobacteria are undoubtedly the most prolific producers of secondary metabolites, and they comprise several commercially and biotechnologically significant species. In this investigation, marine actinobacteria were isolated and evaluated for their antibacterial effectiveness against septicemia pathogens. Effective strains were identified as Nocardiopsis sp., Streptomyces sp., and Pseudonocardia sp. Candidate strains culture filtrates were treated with acetone to precipitate complete proteins. The antibacterial and anti-quorum sensing properties of the crude protein against A. hydrophila MTCC 1739 and P. aeruginosa MTCC 9425 were also examined using the agar well diffusion method. In addition, in vivo investigations of the low molecular weight fraction on Labeorohita demonstrated the fraction's efficacy in reducing septicemia infection. After the 8th day of bathing, fish were found to have recovered.