Study On The Composition,Development And Difference Factors Of Gut Microbiota And Bifidobacterium Communitv In Infants

The colonization and development of bifidobacteria in infants are essential for their health and growth.In recent years,many studies abroad have been carried out on the composition and diversity of gut microbiota in infants.However,the correlation analysis of bifidobacteria community has not been achieved between its species diversity and many factors.The current research mainly explored the effects of delivery modes and feeding methods on gut microbiota and bifidobacteria community in infants,analyzed their development and diversity,and the relationships between them and maternal intestinal flora.And the effect of high abundance of Bifidobacterium animalis subsp.lactis on the bifidobacteria diversity and the source for them were preliminaryly discussed.The main conclusions were as follows:(1)To investigate the effects of delivery modes and feeding methods on gut microbiota and bifidobacteria community in infants,fecal samples of 112 infants within 42 days afterbirth were analyzed by Illumina high-throughput sequencing.The results showed that the composition and diversity of gut microbiota in infants had significant differences.Firmicutes,Proteobacteria and Actinobacteria were major dominant at the phylum level.The abundance of Actinobacteria in vaginal-delivery and breast-fed infants was higher,while that of Firmicutes in caesarean section and formula-fed infants was higher.Unclassified Enterobacteriaceae and Bifidobacterium were the main dominant genus.Vaginal-delivery and breast-fed groups contained more Bifidobacterium and Streptococcus,while caesarean section,formula-fed and mixed-fed groups contained more Enterococcus and Clostridium.B.longum and B.pseudocatenulatum predominated at the bifidobacterial species level,and the abundance of B.animalis subsp.lactis was significantly higher than that in previous reports.B.dentium in vaginal-delivery and breast-fed infants had higher abundance.The diversity of gut microbiota could be reduced significantly by caesarean delivery and formula feeding.Different delivery modes and feeding methods had significant effects on functional genes of gut microbiota,vaginal-delivery and breast-fed infants had more functional genes involved in lipid and protein metabolism,while caesarean section and formula-fed infants had more functional genes involved in carbohydrate metabolism.(2)To analyse the development of gut microbiota and bifidobacteria community in early infants and their possible connection with maternal,23 vaginal-delivery mother-infant pairs were followed up(sampling at 7-day and 42-day afterbirth,respectively).The results showed that the composition and abundance of gut microbiota in infants changed significantly with age,and were significantly different from the maternal intestinal flora.In the composition of gut microbiota,the abundance of Actinobacteria increased,while that of Firmicutes and Proteobacteria reduced.The abundance of Bifidobacterium increased,while that of Streptococcus reduced.B.breve and B.dentium increased,while B.animalis subsp.lactis reduced.In maternal,the abundance of Firmicutes and Bacteroidetes was higher than those in infants,and the genus composition was more abundant,the abundance of Bacteroides and Unclassified Enterobacteriaceae was higher,while that of Bifidobacterium was lower,ofwhich the dominant species were also fewer.In terms of the diversity of gut microbiota,the infants had no significant difference at 7-day and 42-day,while the maternal was significant higher than that of infants.After isolation and genomic comparison of Bifidobacterium from infants and maternal fecal samples,it was found that bifidobacteria in the maternal could be transmitted vertically into the infants gut.(3)The abundance of B.animalis subsp.lactis in some samples was significantly higher than that reported in literature,its effect on the bifidobacteria diversity and the source for them were discussed.The results showed that the high abundance of B.animalis subsp.lactis in infants significantly reduced the abundance and diversity of bifidobacteria.23 B.animalis subsp.lactis were isolated from 50 fecal samples.To compare the differences among them and commercialized strains,their genomes were sequenced and analysed as well as their partial characterization were analysed.And showed that there was no significant genomic difference among the isolates from infants and adults,and their carbohydrate utilization characteristics were basically similar,while only some strains had significant differences in antibiotic tolerance.However,all the strains isolated were not derived from the commercialized strains such as Bb-12,HN019,etc.