Attenuation of Infection in by YtnP, a -acyl Homoserine Lactonase from T-1.

In this experiment, the quorum quenching gene of T-1 was cloned and expressed, and the effect against infection of ATCC 7966 was evaluated in vitro and vivo. The BLAST results revealed a 99% sequence identity between the gene of T-1 and its homolog in sub sp. BSP1, and the dendroGram showed that the similarity in the YtnP protein in T-1 was 100% in comparison with 3610, which was categorized as the Aidc cluster of the MBL family. The AHL lactonase activity of the purified YtnP was detected as 1.097 ± 0.7 U/mL with C6-HSL as the substrate. Otherwise, purified YtnP protein could significantly inhibit the biofilm formation of ATCC 7966 with an inhibition rate of 68%. The MIC of thiamphenicol and doxycycline hydrochloride against reduced from 4 μg/mL and 0.5 μg/mL to 1 μg/mL and 0.125 μg/mL, respectively, in the presence of YtnP. In addition, YtnP significantly inhibited the expression of five virulence factors of ATCC 7966 as well ( < 0.05). The results of inhibition on virulence showed a time-dependence tendency, while the strongest anti-virulence effects were within 4-24 h. In vivo, when the YtnP protein was co-injected intraperitoneally with ATCC 7966, it attenuated the pathogenicity of and the accumulated mortality was 27 ± 4.14% at 96 h, which was significantly lower than the average mortality of 78 ± 2.57% of the injected with 10 CFU/mL of ATCC 7966 only ( < 0.001). In conclusion, the AHL lactonase in T-1 was proven to be YtnP protein and could be developed into an agent against infection of in aquaculture.