Structure,Diversity And Its Influencing Factors Of The Gastrointestinal Tract Flora In The Mouse Embryo

The intestinal tract is the main place for the colonization of the bacteria in the body,and there are many kinds of human intestinal flora.Normal intestinal flora is a natural protective barrier,which is very important to maintain the physical and mental health of human beings.Generally,the intestinal flora in healthy human body maintains a dynamic balance,and the changes in the internal and external environment of the body are likely to break the balance,which can cause or aggravate the disease,and have a serious impact on human health.So it is very important to study the colonization of intestinal flora and its influencing factors.So when does the intestinal flora colonize the gut? Is there any bacterial colonization in the embryonic period? This series of questions is not clear.In order to solve the above problems,this paper used the gastrointestinal tract flora from different periods of embryonic tissue and late pregnancy mouse placenta flora to carry out high flux sequencing,to study on the flora of gastrointestinal and placental tissues of mouse embryos.Secondly,the gastrointestinal tract tissues of different periods and three days after birth were used to carry out the high through-put sequencing to clarify the effect of breast milk on gastrointestinal flora.Lastly,flora from late pregnancy fetal gastrointestinal tissue(differtent litter)and late pregnancy fetal gastrointestinal tissue(same litter)were carried out the high through-put sequencing to elucidate the influence of host genotype on gastrointestinal flora.Planting and breeding of normal flora in the human environment is the inevitable result of the host long time evolution.The establishment of early intestinal flora is closely related to human health,so it is very important to study the gastrointestinal tract flora.Objective:To explore diversity and the composition of bacterial flora in mouse embryonic gastrointestinal tract and the placenta tissue.Further studies on effects of breast milk and host genotype on gastrointestinal microflora in mice.Methods:1.Diversity and the composition of bacterial flora in mouse embryonic gastrointestinal tract and the placenta tissue.24 specimens were collected including 8 fetal gastrointestinal tract tissues from Kunming pregnant mice(12-13 days),8 fetal gastrointestinal tract tissue from Kunming pregnant mice(19-20)and 8 placental tissues from Kunming pregnant mice(19-20).The 24 samples were extracted by DNeasy Blood & Tissue kit for high through-put DNA sequencing.2.Effect of breast milk on the intestinal flora of mice.16 specimens were collected including 8 fetal gastrointestinal tract tissue from Kunming pregnant mice(19-20)and 8 placental tissues from 3 days after birth of Kunming mice.The 16 samples were extracted by DNeasy Blood & Tissue kit for high through-put DNA sequencing.3.The effect of host genotype on the gastrointestinal tract flora in mice.16 specimens were collected including 8 fetal gastrointestinal tract tissue from different litters of Kunming pregnant mice(19-20)and 8 fetal gastrointestinal tract tissue from same litters of Kunming pregnant mice(19-20).The 16 samples were extracted by DNeasy Blood & Tissue kit for high-throughput DNA sequencing.Results:1.Diversity and the composition of bacterial flora in mouse embryonic gastrointestinal tract and the placenta tissue.(1)This study found that Alpha diversity analysis showed that the diversity of gastrointestinal tract flora of early pregnancy embryo group was significantly lower.(2)Beta diversity analysis showed that flora diversity of late pregnancy embryonic gastrointestinal group and late pregnancy placenta group were small difference.(3)The results showed that at the level of phylum,Proteobacteria,Bacteroidetes,Actinobacteria and Firmicutes were predominant bacterial phyla in all specimens.The relative content of Proteobacteria,Actinobacteria and Firmicutes in the gastrointestinal tract of the early pregnancy embryo group were different from those of the late pregnancy embryonic gastrointestinal group and late pregnancy placenta group(P<0.05).However,there was no significant difference in the relative contents of the four dominant groups in the late pregnancy embryonic gastrointestinal group and late pregnancy placenta group(P > 0.05).There were nine predominant bacterial families in level of family,which had no significant difference between the three groups in the relative content of dominant bacteria of Enterobacteriaceae,Shewanella,Moraxella(P > 0.05).But relative content of Staphylococcaceae,Pseudomonadaceae,Caulobacteraceae,Micrococcaceae and Sphingomonadaceae in the gastrointestinal tract of the early pregnancy embryo group were different from those of the late pregnancy embryonic gastrointestinal group and late pregnancy placenta group(P < 0.05).Only there were differences in the relative contents of Sphingomonadaceae in the late pregnancy embryonic gastrointestinal group and late pregnancy placenta group(P<0.05).From the species of flora,early pregnancy and late pregnancy fetal gastrointestinal flora were 65.44% and 62.73% respectively the same as the late pregnancy placenta tissue bacterial flora.From the abundance of bacteria,at the level of family,three groups of the same content of bacteria accounted for 78.16%,72.53% and 65.78% respectively.This indicated that about 2/3 of the bacteria in the three groups were consistent.2.Effect of breast milk on the intestinal flora of mice.This paper found that flora diversity of 3 day after the birth of young rat gastrointestinal group and bacterial diversity of late pregnancy embryonic gastrointestinal group was relatively bigger difference.In the analysis of microbial community structure,fetal gastrointestinal tract of dominant bacteria were reduced significantly after birth in mice,but content of Pasteurellaceae,Lactobacillaceae and Streptococcaceae that was very low in the embryonic period increases obviously after breast feeding the mice.3.The effect of host genotype on the gastrointestinal tract flora in mice.Research showed:(1)The types of bacteria in the late pregnancy embryonic gastrointestinal group(same litter)were more abundant than those in the late pregnancy embryonic gastrointestinal group(different litter).(2)compared with late pregnancy embryonic gastrointestinal group(different litter),The structure of the bacteria in the late pregnancy embryonic gastrointestinal group(same litter)was similar within the sample.(3)structure of late pregnancy embryonic gastrointestinal group(same litter)and late pregnancy embryonic gastrointestinal group(different litter)embryonic gastrointestinal flora existed obvious difference.at the level of phylum,comparison of late pregnancy embryonic gastrointestinal group(same litter)and late pregnancy embryonic gastrointestinal group(different litter),the relative content of the four dominant phylum(Proteobacteria,Bacteroides,Actinomyces,Firmicutes)had significant difference(P<0.05).At the level of family,comparison of late pregnancy embryonic gastrointestinal group(same litter)and late pregnancy embryonic gastrointestinal group(different litter),the relative content of Enterobacteriaceae,Micrococcaceae,Staphylococcus had significant difference(P<0.05).Conclusion:1.It was proved that the gastrointestinal bacterial flora of mouse embryos and the placenta tissue bacterial flora were colonized,2.Breast milk and host genotype were the important factors that affect the gastrointestinal tract flora.