velezensis CPA1–1 carried genes encoding the biosynthesis of various peptidoglycans, polyketone compounds and antimicrobial proteins, such as srfAA, ituA, fenA, dhbA, bmyA, beaS, and dfnA. Through PCR amplification, the results showed that B. CPA1–1 has better antibacterial effects on indicator bacteria, Aeromonas veronii, Plesimonas shigelloides, Aeromonas hydrophila, Vibrio parahaemolyticus, Citrobacter freundii, and the average diameter of the inhibition zones were 31.2 mm, 26.5 mm, 23.3 mm, 21.4 mm and 10.5 mm, respectively. The strain CPA1–1 could grow at a salinity of 5–60‰, and the optimal salinity was 5–20‰. The optimum pH value was 5–9, and the strain was severely inhibited when the pH was lower than 3 or higher than 11. The results showed that the optimal growth temperature of strain CPA1–1 was 25–37 ☌, and the growth of the strain was slow under 20 ☌. The characteristics of growth, antimicrobial spectrum, the carrying of antibiotic-related genes and safety analysis of the strain were also studied. It was identified as Bacillus velezensis through morphological, physiological and biochemical characteristics in combination with 16S rRNA and gyrB sequence analysis. The strain CPA1–1 with better antibacterial ability was isolated and screened from healthy Macrobrachium nipponense by spot inoculation for the first time.
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