Influence Of Probiotic Lactobacillus Casei Zhang On Gut Microbiota Of Healthy Youths From Different Locations

As a means to improve the quality of life and prevent diseases,the popularity of probiotics and related products has grown year by year.This study was carried out to reveal whether the intake of Lactobacillus casei Zhang(LCZ)has probiotic effects on healthy youths from different locations and the factors that affect its effects.Previous studies have found that the composition and changes of gut microbiota are closely related to human health,and the occurrence and progression of many diseases.Therefore,the effect of LCZ intake on gut microbiota structure and major probiotics bacteria,such as lactic acid bacteria(LAB)and Bifidobacterium can be used as evaluation indicators.In this study,106 healthy young volunteers,aged between 18 to 28,were recruited from from Hohhot,Inner Mongolia;Urumqi,Xinjiang;Gannan tibetan autonomous prefecture,Gansu and Ulaanbaatar,Mongolia;Singapore;Yogyakarta,Indonesia,respectively.During the experimental period,volunteers ate 2g of LCZ powder(0.5×1010 CFU/g)packaged independently after lunch for 14 days.Fecal samples of volunteers were collected at the 0,7th and 14th day,respectively,during LCZ treatment,and at the 14th day after treatment.At the same time,the dietary habits of the volunteers were investigated.We designed and screened a pair of specific primers for LAB,combined with the existing specific primers of bifidobacteria in our laboratory,we can meet the needs of the analyzing the above two types of low-abundance microbiota in gut.And on this basis,combined with molecular biological methods,PacBio SMRT third generation sequencing was employed in this study.The full length of bacterial 16S rRNA,the specific target fragment of LAB and the specific target fragment of Bifidobacteria were used as targets for amplification,sequencing,and then bioinformatics analysis were carried out.The characteristics of gut microbiota of healthy volunteers in different regions and their relationship with dietary habits were revealed.Besides,the differential effects of LCZ intake on gut microbiota of volunteers from different locations were analyzed.On basis of obtained results,the following conclusions were made:(1)The gut microbiota of healthy volunteers mainly composed of Firmicutes,Bacteroides,Proteobacteria,Actinomycetes and Tenericutes at the phylum level.There was no absolute correlation between obesity and Firmicutes/Bacteroides index in volunteers.At the genus level,gut microbiota mainly consisted of Prevotella,Bacteroides,Faecalibacterium,Eubacterium,Blautia,Ruminococcus,etc.At the species level,gut microbiotamainly composed of Prevotella copri,Faecalibacterium prausnitzii,Bacteroides dorei,Eubacterium rectale etc.Faecalibacterium prausnitzii was the only species detected in all volunteers.Region is the most critical factor affecting the composition of gut microbiota in volunteers,outweighing obesity and gender.Diet also plays a role in gut microbiota composition.Youths from different locations can be divided into 2 enterotypes:FB enterotype and PF enterotype.The former was characterized by Faecalibacterium prausnitzii and Bacteroides dorei,and the latter was characterized by Prevotella copri and Faecalibacterium prausnitzii.The relative abundance of Prevotella copri was the most important factor responsible for the abundance and diversity of gut bacteria.Together with Bacteroides dorei,they determine the overall composition of gut microbiota of volunteers(2)The influence of LCZ on gut microbiota differs in volunteers from different locations,and it was affected jointly by regional related factors and the composition of individual primitive gut microbiota.LCZ increased the relative abundance of some beneficial bacteria such as Lactobacillus,Roseburia,Coprococcus,Eubacterium rectale.In addition,it inhibited the growth of harmful bacteria such as Blautia,Ralstonia pickettii.These changes reduced the risk of Crohn's disease,inflammatory bowel disease and food allergy,etc.,and potentially enhanced the functions of digestive and immune system in hosts.After stopping LCZ intake,the gut microbiota of volunteers tended to recover,suggesting that it needs long-term and sustained intake of probiotic LCZ to maintain its beneficial effect.Lipopolysaccharide biosynthesis pathways were significantly enriched in the PF enterotypes population,while a variety of essential amino acid synthesis related modules were significantly enriched in the FB enterotype population.LCZ increased the metabolic pathways of amino acid transport or transport system in PF enterotype population,decreased the relative abundance of lipopolysaccharide biosynthesis module in both enterotypes,and promote the metabolic function of gut microbiota in volunteers to change in favor of host health.(3)The gut LABs of volunteers mainly composed of Lactobacillus ruminis,Streptococcus salivarius,Streptococcus thermophilus,Lactobacillus delbrueckii,Enterococcus durans,Weissella confuse,etc.The Bifidobacterium(B.)mainly composed of B.adolescentis,B.breve,B.catenulatum,B.bifidum,B.angulatum,etc.Compared with LAB,the a diversity of Bifidobacterium may be much more affected by the overall composition of gut microbiota.After LCZ intake,the abundance of lactic acid bacteria in the intestinal tract of volunteers in all locations was increased.After stopping LCZ intake,the abundance of LAB in the gut microbiota of volunteers tended to decreased.In addition,LCZ intake did not have a significant impact on the a diversity and species composition of Bifidobacteria in volunteers.