Figure 2

Safety assessments of the probiotic isolate, P. xiamenensis, and pathogenic strain, E. piscicida. In vivo safety assessment was conducted by exposing zebrafish larvae to different concentrations of P. xiamenensis in egg water. (A) Schematic representation for the experimental schedule of P. xiamenensis exposure to the zebrafish larvae. (B) Kaplan−Meier survival curves of zebrafish larvae upon exposure to the different concentrations of P. xiamenensis. (C) In vitro cytotoxicity assay. Fathead minnow (FHM) fish epithelial cells were either exposed to P. xiamenensis probiotic isolate, or E. piscicida pathogenic strain. After 1 h of incubation, cells were washed with PBS and non-internalized bacteria were eliminated by gentamycin treatment. The cells were replenished with complete growth media and further incubated for 12 h. After 12 h incubation, the cells were subjected to propidium iodide (PI) staining and observed under a fluorescent microscope. Images were taken at 200 × magnification.