Regulation of serotonin production by specific microbes from piglet gut

Background Serotonin is an important signaling molecule that regulates secretory and sensory functions in the gut.Gut microbiota has been demonstrated to affect serotonin synthesis in rodent models.However,how gut microbes regulate intestinal serotonin production in piglets remains vague.To investigate the relationship between microbiota and serotonin specifically in the colon,microbial composition and serotonin concentration were analyzed in ileum-cannulated piglets subjected to antibiotic infusion from the ileum when comparing with saline infusion.Microbes that correlated positively with serotonin production were isolated from piglet colon and were further used to investi-gate the regulation mechanisms on serotonin production in IPEC-J2 and a putative enterochromaffin cell line RIN-14B cells.Results Antibiotic infusion increased quantities of Lactobacillus amylovorus(LA)that positively correlated with increased serotonin concentrations in the colon,while no effects observed for Limosilactobacillus reuteri(LR).To understand how microbes regulate serotonin,representative strains of LA,LR,and Streptococcus alactolyticus(SA,enriched in feces from prior observation)were selected for cell culture studies.Compared to the control group,LA,LR and SA supernatants significantly up-regulated tryptophan hydroxylase 1(TPH1)expression and promoted serotonin production in IPEC-J2 cells,while in RIN-14B cells only LA exerted similar action.To investigate potential mechanisms mediated by microbe-derived molecules,microbial metabolites including lactate,acetate,glutamine,andγ-aminobutyric acid were selected for cell treatment based on computational and metabolite profiling in bacte-rial supernatant.Among these metabolites,acetate upregulated the expression of free fatty acid receptor 3 and TPH1 while downregulated indoleamine 2,3-dioxygenase 1.Similar effects were also recapitulated when treating the cells with AR420626,an agonist targeting free fatty acid receptor 3.Conclusions Overall,these results suggest that Lactobacillus amylovorus showed a positive correlation with sero-tonin production in the pig gut and exhibited a remarkable ability to regulate serotonin production in cell cultures.These findings provide evidence that microbial metabolites mediate the dialogue between microbes and host,which reveals a potential approach using microbial manipulation to regulate intestinal serotonin biosynthesis.

一株异养型细菌对无机硫化物的降解特性和培养条件优化

畜禽屠宰加工、鱼粉饲料加工等一些食品工业生产过程中会释放出大量的硫化氢恶臭气体,导致周边环境的严重污染。为实现以培养异养型细菌脱除硫化氢气体的目的,取分离到的异养脱硫细菌XJ-2,通过诱变筛选得到一株高效脱硫菌株ZJNB-B3,其脱硫率达97%。基于形态学研究、API 50 CHB生理生化鉴定及16S r RNA基因测序,鉴定该菌为蜡状芽胞杆菌Bacillus cereus ZJNB-B3。该菌Gen Bank登录号为MF679650。降解特性研究表明,ZJNB-B3菌株对有毒的硫化物有较高耐受性,耐受上限高达300 mg/L。采用响应面法优化环境因素对菌株降解硫化物效率的影响,得到在最适培养温度30℃下,初始S^2–浓度为211.8 mg/L、初始p H值6.72、接种量为5.04%时,菌株氧化脱硫效果最显著,经过实测在48 h产生的硫酸盐浓度为63.8 mg/L,脱硫率达97.3%。菌株在氧化硫化物时不会产生硫酸抑制菌株的生长,可以在p H值温和的环境条件下脱硫,因此,该菌有较高的工业应用价值。本研究为异养型细菌应用于工业反应器脱除硫化氢恶臭气体提供了小试研究基础。