Attenuation of <i>Aeromonas hydrophila</i> Infection in <i>Carassius auratus</i> by YtnP, a <i>N</i>-acyl Homoserine Lactonase from <i>Bacillus licheniformis</i> T-1

• Main Authors: Mengfan Peng (Author), Wentao Tong (Author), Zhen Zhao (Author), Ling Xiao (Author), Zhaoyue Wang (Author), Xuanming Liu (Author), Xuanhao He (Author), Zengfu Song (Author)
• Format: Book
• Published: MDPI AG, 2021-05-01T00:00:00Z.
• Subjects: article
• Online Access: Connect to this object online.
• Notes: 10.3390/antibiotics10060631; 2079-6382
• Keywords: YtnP; <i>Bacillus licheniformis</i>; <i>Aeromonas hydrophila</i>; anti-virulence; Therapeutics. Pharmacology; RM1-950
• Source: Antibiotics, Vol 10, Iss 6, p 631 (2021)

In this experiment, the quorum quenching gene <i>ytnP</i> of <i>Bacillus licheniformis</i> T-1 was cloned and expressed, and the effect against infection of <i>Aeromonas hydrophila</i> ATCC 7966 was evaluated in vitro and vivo. The BLAST results revealed a 99% sequence identity between the <i>ytnP</i> gene of T-1 and its homolog in <i>B.</i><i>subtilis</i> sub sp. BSP1, and the dendroGram showed that the similarity in the YtnP protein in T-1 was 100% in comparison with <i>B.</i><i>subtilis</i> 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 <i>A.</i><i>hydrophila</i> ATCC 7966 with an inhibition rate of 68%. The MIC of thiamphenicol and doxycycline hydrochloride against <i>A. hydrophila</i> 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 <i>hem, ahyB, ast, ep, aerA</i> of <i>A. hydrophila</i> ATCC 7966 as well (<i>p</i> < 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 <i>A. hydrophila</i> ATCC 7966, it attenuated the pathogenicity of <i>A. hydrophila</i> 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 <i>Carassius auratus</i> injected with 10⁸ CFU/mL of <i>A. hydrophila</i> ATCC 7966 only (<i>p</i> < 0.001). In conclusion, the AHL lactonase in <i>B. licheniformis</i> T-1 was proven to be YtnP protein and could be developed into an agent against infection of <i>A. hydrophila</i> in aquaculture.