饲用枯草芽孢杆菌HGcc-1对鲤肠肝健康、血清补体及肠道菌群的影响

为了研究枯草芽孢杆菌HGcc-1对鲤肠肝健康、血清补体和肠道菌群的影响,实验选择体质量为(13.10±0.39) g健康鲤,随机分为HGcc-1添加组和对照组,养殖20周后测定生长指标,用试剂盒检测了鲤血清内毒素(LPS)、谷丙转氨酶(ALT)、谷草转氨酶(AST)、总补体和溶菌酶,并对肠道菌群进行了16S rRNA测序,同时将添加组和对照组的肠道菌群转接至无菌斑马鱼,然后检测无菌斑马鱼体内毒素结合蛋白(LBP)、ALT、AST的水平和C3、C4基因表达量;最后还检测了HGcc-1直接作用于无菌斑马鱼时,无菌斑马鱼的ALT、AST的水平和C3、C4基因表达量。结果显示,HGcc-1对鲤的增重率无显著影响;与对照组相比,饲料中添加HGcc-1显著降低鲤血清内毒素、ALT和AST水平;同时HGcc-1添加组血清总补体水平显著升高。在门水平上,HGcc-1添加组中梭杆菌门丰度比对照组增加了47.1%;变形菌门丰度比对照组减少了70.7%;在属水平上,HGcc-1添加组中鲸杆菌属(的丰度比对照组增加了47.1%;柠檬酸杆菌属和气单胞菌属(的丰度比对照组分别减少了56.6%和70.9%。利用无菌斑马鱼模型进一步发现,HGcc-1添加组鲤肠道菌群显著降低了无菌斑马鱼LBP含量和AST水平,显著上调了无菌斑马鱼补体C3和C4基因表达;与此同时,HGcc-1与无菌斑马鱼直接互作也降低了鱼体ALT和AST水平。研究表明,饲料中添加枯草芽孢杆菌HGcc-1能够改善鲤肠肝健康、血清补体以及肠道菌群稳态。本研究为枯草芽孢杆菌HGcc-1的下一步应用奠定了理论基础。

Effects of dietary Bacillus subtilis HGcc-1 on gut and liver health, serum complement and gut microbiota of common carp fingerlings (Cyprinus carpio)

In order to study the effects of Bacillus subtilis HGcc-1 on the gut and liver health, serum complement and gut microbiota of Cyprinus carpio fingerlings, healthy C. carpio fingerlings with a body weight of (13.10±0.39) g were selected, and randomly divided into HGcc-1 supplementation group and control group, and after 20 weeks of feeding, the growth indicators were measured, and the C. carpio serum endotoxin (LPS), Alanine aminotransferase (ALT), Aspartate aminotransferase (AST), total complement and lysozyme were detected, and 16S rRNA sequencing of the gut microbiota was made. At the same time, the gut microbiota induced by HGcc-1 supplement group and the control group were transferred to germ free Danio rerio, and then the levels of endotoxin binding protein (LBP), ALT and AST and the expression levels of C3 and C4 genes of germ free D. rerio were measured; finally, the levels of ALT and AST and the expression levels of C3 and C4 genes in germ free D. rerio were tested when HGcc-1 directly acted on germ free D. rerio. The results showed that HGcc-1 had no effect on the weight gain rate of C. carpio, but adding HGcc-1 significantly reduced the level of serum endotoxin, ALT and AST. The serum total complement level of the HGcc-1 supplement group was significantly increased, compared with control group. The 16S rRNA sequencing results showed that at the phylum level, the HGcc-1 supplement diet group increased the abundance of Fusobacterium by 47.1% compared to control group; the abundance of Proteobacteria was decreased by 70.7% compared with the control group; at the genus level, the HGcc-1 supplement diet group increased the abundance of Cetobacterium by 47.1% compared with the control group; the abundances of Citrobacter and Aeromonas were reduced by 56.6% and 70.9% respectively, compared with the control group. And it was further observed that the intestinal microbiota of HGcc-1 addition group decreased the content of endotoxin binding protein (LBP) and level of AST of the germ free (GF) D. rerio, and significantly increased the gene expression of complement component 3 and the complement component 4 (C3 and C4) of the GF D. rerio. At the same time, the direct interaction between HGcc-1 and GF D. rerio also decreased the ALT and AST levels of the GF D. rerio. This study shows that dietary B. subtilis HGcc-1 can improve the gut and liver health, serum complement and intestinal microbiota homeostasis of C. carpio fingerlings. This study laid a theoretical foundation for the further application of B. subtilis HGcc-1.