Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong, China; Department of Food Industry, Shandong Institute of Commerce and Technology, No.4516 Lvyou Road, Jinan, China.
Shandong Provincial Key Laboratory of Animal Resistance Biology, College of Life Sciences, Shandong Normal University, Jinan, Shandong, China.
Fish Shellfish Immunol. 2024 Dec;155:109997. doi: 10.1016/j.fsi.2024.109997. Epub 2024 Oct 31.
Peptidoglycan recognition protein 2 (PGRP2) plays a role in regulating immune defense in fish. Our previous studies found that CcPGRP2 helped maintain the integrity of the intestinal mucosa of carp and could bind and agglutinate bacteria when infected with A. hydrophila. However, its effect on the structure of the microbiota has not yet been clarified. Therefore, it is necessary to explore the effect of CcPGRP2 on the intestinal microbiota structure in fish.
In the present study, common carp were injected with CcPGRP2 protein intraperitoneally and high-throughput sequencing technology was used to study the difference in intestinal microbiota structure. Firstly, the variations in α- and β-diversity of the intestinal microbiota of common carp in control and treatment groups were tested, and the results indicated that intraperitoneal injection of A. hydrophila significantly reduced the microbial α-diversity (within-samples) and β-diversity (between-samples) in common carp gut samples, but CcPGRP2 protein could alleviate these reduction, no matter in the case of simultaneous injection of CcPGRP2 protein and A. hydrophila or a intermitted injection with first injection of CcPGRP2 and then A. hydrophila after 6 h. Subsequently, the intestinal microbiota structures of common carp on various taxonomic levels were interrogated under the treatments.
The data revealed that the abundance of intestinal pathogen Aeromonas was reduced when CcPGRP2 was injected in the common carp, and the alleviation effect was better when CcPGRP2 was injected with A. hydrophila at the same time, implying the function of CcPGRP2 in inhibiting intestinal dysbiosis. Moreover, the functional prediction demonstrated the possible physiological shifts and the influences of microbes on the environment after the common carp is injected with A. hydrophila and CcPGRP2. Finally, the bacterial interaction patterns results showed that the groups injected with A. hydrophila were diverted away from the control group in terms of clustering relationship, while the injection of CcPGRP2 could reverse the effect of A. hydrophila and keep the microbial structure closer to that of the control group; meanwhile, the effect of simultaneous injection of A. hydrophila and CcPGRP2 was better than that of intermitted injections.
All the results in this study suggest that the CcPGRP2 could alleviate the internal dysbiosis under pathogen infection, which will provide a foundation for disease resistance breeding.
肽聚糖识别蛋白 2（PGRP2）在鱼类的免疫防御中发挥作用。我们之前的研究发现，CcPGRP2 有助于维持鲤鱼肠道黏膜的完整性，并且在感染嗜水气单胞菌时可以结合和凝集细菌。然而，其对微生物区系结构的影响尚不清楚。因此，有必要探讨 CcPGRP2 对鱼类肠道微生物区系结构的影响。
本研究中，通过腹腔注射 CcPGRP2 蛋白，使用高通量测序技术研究肠道微生物区系结构的差异。首先，检测对照组和治疗组鲤鱼肠道微生物区系的 α-多样性和β-多样性的变化，结果表明，腹腔注射嗜水气单胞菌显著降低了鲤鱼肠道样本的微生物 α-多样性（样本内）和β-多样性（样本间），但 CcPGRP2 蛋白可以减轻这种降低，无论同时注射 CcPGRP2 蛋白和嗜水气单胞菌，还是先注射 CcPGRP2 蛋白 6 小时后再注射嗜水气单胞菌。随后，在各种分类水平上检测了 CcPGRP2 处理下鲤鱼的肠道微生物区系结构。
数据显示，当 CcPGRP2 被注射到鲤鱼体内时，肠道病原体气单胞菌的丰度降低，同时注射 CcPGRP2 和嗜水气单胞菌的缓解效果更好，这表明 CcPGRP2 具有抑制肠道菌群失调的功能。此外，功能预测表明，在鲤鱼注射嗜水气单胞菌和 CcPGRP2 后，可能会发生生理转变以及微生物对环境的影响。最后，细菌相互作用模式的结果表明，注射嗜水气单胞菌的组在聚类关系上与对照组分离，而注射 CcPGRP2 可以逆转嗜水气单胞菌的作用，使微生物结构更接近对照组；同时，同时注射嗜水气单胞菌和 CcPGRP2 的效果优于间歇性注射。
本研究的所有结果表明，CcPGRP2 可以在病原体感染下缓解肠道内的失调，这将为抗病性育种提供基础。
