Growth Characteristics and Tracing Antagonistic Properties of Bacillus flexus and Bacillus subtilis as Antibacterials to Overcome the Attack of Aeromonas hydrophila Bacteria on Fish

This research was conducted to assess the antibacterial potential of Bacillus flexus and Bacillus subtilis against Aeromonas hydrophila. Bacterial samples came from the stock of the FPIK Unpad Biotechnology Laboratory. This research was conducted in July 2020 - May 2021 in Laboratorium Biotechnology FPIK Padjadjaran University. This research was conducted using qualitative and quantitative descriptive analysis. Bacteria were collected using the purposive sampling method, Observation of the growth curve using the turbidimetric method, and the disc diffusion method for the inhibition zone test with bacterial supernatant treatment with a concentration of 50%, a concentration of 100%, bacterial culture, chloramphenicol antibiotics with a concentration of 4000 ppm as a positive control. The results showed that B. flexus bacteria experienced an exponential phase at 6 to 12 hours, after which it entered a stationary phase at 14 to 72 hours. B. subtilis bacteria experienced an exponential phase at 20 hours. Until 40 hours, then experiencing a stationary phase at 42 hours to 72 hours, and the growth of A. hydrophila bacteria experiences an exponential phase at 6 hours to 28 hours, the stationary phase at 30 to 28 hours 72. Based on the results of the inhibition zone test, it showed the formation of the inhibition zone only in the positive control treatment, while the supernatant and bacterial cultures of B. flexus and B. subtilis didn’t form an inhibition zone.