Antibacterial efficacy of seagrass Cymodocea serrulata-engineered silver nanoparticles against prawn pathogen Vibrio parahaemolyticus and its combative effect on the marine shrimp Penaeus monodon

Green synthesis of silver nanoparticles (AgNPs) was undertaken using seagrass Cymodocea serrulata, and their characteristics were confirmed by indispensible instrumental analysis. UV spectroscopy analysis (UV) showed a strong peak in the wavelength of 431 nm, resembling the surface resonance peak (SPR) specific for AgNPs. Zeta potential analysis confirmed the stability (-28.4 +/- 0.35 mV) of AgNPs. Transmission electron microscopy (TEM) result shows that the particles were in the size range of 40.49-66.44 nm. X-ray diffraction analysis (XRD) confirms the crystalline nature of AgNPs. Fourier transform infra-red spectroscopy (FTIR) analysis indicated the possible presence of polyphenol and protein encapsulates on AgNPs. Antibacterial efficacy of the AgNPs was tested against Vibrio parahaemolyticus induced vibriosis in the juvenile shrimps Penaeus monodon. Shrimps were fed on normal formulated feeds supplemented either with an aqueous extract of seagrass or AgNPs. Half of the experimental groups were infected with Vibrio parahaemolyticus (MTCC 451) (100 mu l-LD50 dose) after 14 days of scheduled feeding. After two weeks of experiment about 65% mortality could be observed in Vibrio challenged control prawns. 25.1% mortality was observed in prawns supplemented with seaweed aqueous extract, whereas the mortality was 15.2% in seaweed SNP supplemented group. Hepatopancreas samples of all the groups were subjected to biochemical and histological studies at the culmination of the feeding experiment (28 days). In vivo analysis of biochemical parameters (GOT, GPT, LDH, ALP and ACP) and the histological architecture provided evidence for the antibacterial effects of AgNPs.