香坊肠球菌和罗伊氏乳杆菌在无菌猪肠道中的定殖

Colonization of germ-free pig guts by Enterococcus xiangfangensis and Lactobacillus reuteri strains from different origins

摘要:

【背景】已有研究表明，微生物在宿主肠道中的定殖受宿主、肠道环境、微生物物种特性和菌株来源等多个因素的影响。一般认为，来源于同类宿主的微生物菌株，在该类宿主肠道中具有定殖优势，但缺乏在物种和菌株水平上研究微生物自身特性在宿主肠道中定殖的研究报道。【目的】将不同来源(同类宿主肠道、非同类宿主肠道和非肠道环境)、具有不同生物学特性的3株香坊肠球菌(Enterococcus xiangfangensis)和4株罗伊氏乳杆菌(Lactobacillus reuteri)对无菌猪肠道进行定殖，在物种和菌株2个水平上探究物种特性和菌株来源对宿主肠道定殖的偏好性，揭示影响微生物定殖效率的关键因素。【方法】在本项研究中，将从藏猪(Tibetan pigs)、小鼠(ob/ob mice)、食蟹猴(Macaca fascicularis)和发酵食品中分离得到的多株香坊肠球菌和罗伊氏乳杆菌，制成混合菌剂对无菌巴马香猪(Bama miniature pig)进行为期4周的饲喂，并通过实时荧光定量PCR方法检测这7株菌在无菌猪肠道中的定殖情况。【结果】在物种水平上，香坊肠球菌和罗伊氏乳杆菌在无菌猪体内具有相近的定殖细胞数目。但是在菌株水平上，小鼠来源的香坊肠球菌(EX-MS)和罗伊氏乳杆菌(LR-MS)定殖的细胞数目显著高于其他5株菌，表明小鼠来源的菌株具有定殖优势。在体外混合培养中，将3株香坊肠球菌和4株罗伊氏乳杆菌分别等比例混合培养72 h后，发现香坊肠球菌EX-MS菌株的细胞数目高于香坊肠球菌EX-MK和EX-PG菌株；在罗伊氏乳杆菌中，4株菌的细胞数目相近。7株菌相互作用表明，EX-MS菌株对EX-MK和EX-PG菌株均有明显的抑制作用，但对4株罗伊氏乳杆菌无抑制作用。【结论】本次定殖实验的结果表明，在物种水平上，香坊肠球菌和罗伊氏乳杆菌均具有在无菌猪肠道中良好的定殖能力；但在菌株水平上，小鼠来源的香坊肠球菌EX-MS菌株和罗伊氏乳杆菌LR-MS菌株具有定殖优势；同时发现，小鼠来源的香坊肠球菌EX-MS菌株通过抑制同物种的EX-PG和EX-MK菌株，获得了在宿主肠道中的定殖优势。

Abstract:

[Background]Previous studies suggested that the colonization of microorganisms in the host՚s intestinal tract was affected by both host and microbial behaviors,including many factors such as the host's intestinal environment,the origin of microbial strain and species characteristics.It is generally believed that the microbial strains have advantages in colonizing the intestinal tract of the same category of hosts,but there were few reports on the colonization of host intestinal tract at the species and strain levels.[Objective]This study aims to explore the colonization of host guts by different microbial species and strains,and to reveal the key factors affecting the rate of microbial colonization.[Methods]In this study,three strains of Enterococcus xiangfangensis and four strains of Lactobacillus reuteri from Tibetan pigs,ob/ob mice,Macaca fascicularis and fermented food were prepared into a mixed agent to feed germ-free Bama miniature pigs for four weeks,and the colonization of germ-free pig guts by these seven strains were detected with quantitative real-time PCR.[Results]At the species level,E.xiangfangensis and L.reuteri colonized similar number of cells in the germ-free pigs.However,at the strain level,E.xiangfangensis EX-MS and L.reuteri LR-MS that originated from mice colonized more cells than the other five strains,indicating that these mouse-originated strains had an advantage of colonizing germ-free pigs.After the three strains of E.xiangfangensis and four strains of L.reuteri were respectively mixed in equal proportions and cultured for 72 h,E.xiangfangensis EX-MS colonized more cells than EX-MK and EX-PG,while the four strains of L.reuteri colonized similar number of cells.The interaction test between the seven strains demonstrated that EX-MS exerted inhibitory effects on EX-MK and EX-PG,while it had no inhibitory effect on the four strains of L.reuteri.[Conclusion] At the species level,both E.xiangfangensis and L.reuteri had good ability of colonizing the intestinal tract of germ-free pigs.At the strain level,E.xiangfangensis EX-MS and L.reuteri LR-MS that originated from mice had colonization advantages.Moreover,EX-MS gains the colonization advantage in the host intestine by inhibiting the growth of E.xiangfangensis EX-PG and EX-MK respectively originated from Tibetan pigs and M.fascicularis.