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

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.

Key words:gut microbiota;Enterococcus xiangfangensis;Lactobacillus reuteri;germ-free pigs;colonization preference