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Fig. 2.

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Fig. 2. Lytic activity of ST01 against S. typhimurium. (A) The peptidoglycan-degrading activity of ST01 was determined by plate lysis assay using a plate containing an autoclaved culture of Salmonella typhimurium ATCC 14028. SoluBL21 carrying pET21a (Empty) or pAS008 was grown in LB containing ampicillin until culture reached the midexponential phase and expression of ST01 was induced with the addition of 0 mM (-) or 1 mM IPTG (+). After 6 h culture at 37°C, 1 μl of each culture was spotted on the plate and air dried. The plates were incubated at 37°C overnight. The clear zone represents the lytic activity of ST01. (B) The antimicrobial activity of ST01 against S. typhimurium ATCC 14028 was tested by CFU reduction assay. Exponentially grown bacterial cells were adjusted as 1 × 106 CFU in 20 mM Tris-HCl pH 7.5 and treated with 0, 0.2, and 2 μM of purified ST01 at 37°C for 2 h. The surviving bacterial cells were counted by plating on an LB plate. (C) The antimicrobial activity of ST01 was tested against P. aeruginosa PA01, A.baumannii ATCC 17978, K. pneumonia KCTC 2208, E. coli ATCC 8739, E. aerogenes F276, E. cloacae ATCC 13047 by CFU reduction assay. The bacterial cells were prepared as described above and treated with 0, 0.125, 0.25, 0.5, 1 μM of ST01. The experiments were repeated at least three times and data are presented as mean ± SD. Significance is shown as *p < 0.0392; **p < 0.0074; n.s. = not significant.
J. Microbiol. Biotechnol. 2022;32:816~823
© J. Microbiol. Biotechnol.