| Pu’er tea is a kind of post-fermented tea,which is helpful for reducing weight,lipid and blood sugar,and anti-tumor,anti-oxidation,antibacterial and anti-inflammatory etc.Microorganisms have an important influence on the safety,quality and flavor of Pu’er tea.At present,there are much concerning about the safety problems of Pu’er tea caused by fungi and its toxins,but there are quite few studies on bacteria safety.There is little research on the effects of Pu’er tea on ulcerative colitis.Therefore,the safety of Bacillus and the effect of decoction in Pu’er tea on DSS-induced colitis in mice were studied as following.Firstly,the microorganisms in Pu’er tea were isolated and evaluated for its safety.The Pu’er tea was brewed by sterile water and boiling water,respectively.Isolates were identified by 16 S rDNA sequencing and physiology biochemistry test.The survival ratio of isolates in simulated gastrointestinal fluid and its virulence gene consititution was detected.The inhibitory effect of Pu’er tea on the expression of toxin gene of Bacillus cereus was monitored by qPCR techniques in cell culture model.The results showed that a total of 45 strains of bacteria were obtained from sterile water-soaked tea leaves,26 of which were Bacillus cereus.Seven strains(FBCE01,FBCE06,FBCE10,FBCE14,FBCE20,FBCE26 and FBCE29)were obtained from boiling water-soaked tea,and proved to be Bacillus cereus containing two or three of virulence genes(cytK,nheA and hblD),respectively,exhibiting strong resistance in simulated gastro-intestinal fluid.Pu’er tea could effectively reduce the damage of cells caused by Bacillus cereus and down-regulate mRNA level of enterotoxin of Bacillus cereus(P < 0.01).Secondly,the effect of Pu’er tea soup on DSS induced colitis was investigated.50 of C57BL/6 mice were randomly divided into 5 groups.One week before DSS-inducing,mice were given distilled water(DSS group),high(H+DSS: 40 mg/20 g),medium(M+DSS: 20 mg/20 g),and low(L+DSS: 10 mg/20 g)concentration’s Pu-erh tea soup,following by drinking DSS one week,then the indexes of mice were examined,including DAI index,mouse body weight,colon length,colon tissue HE staining,colon histopathological score,immunohistochemical staining,expression of inflammatory factors in colon tissue,intestinal permeability,expression of p-p38 and p-p65 protein,etc.The results showed that the stools,body weight and colon length in both M+DSS and the H+DSS group were non-significant difference with control,and its colon tissue was intact and undamaged,no inflammatory cell infiltration took place.The TNF-α,IL-1β,IL-6,IL-10,MCP-1 and COX-2 were significantly down-regulated in colon tissues,intestinal permeability did not change in mice,and the expression of p-p38 and p-p65 protein in the colon was also significantly lower.Finally,the effect of Pu’er tea decoction on the intestinal flora of DSS-induced colitis mice was explored.High-throughput sequencing of intestinal flora in mice was carried out.When compared with DSS group,Shannon index,Chao index,Sobs index,and Simpson index of the microbial flora of the colitis mice fed with high-,middleand low-dose Pu’er tea decoction remained at normal levels as control,indicating that Pu’er tea decoction can effectively prevent the decrease of DSS-induced intestinal microbial diversity.Results of PCA,PCoA,NMDS and UPGMA cluster analysis showed that the structure of intestinal microflora in Pu’er tea decoction group was closer to the control group,indicating that Pu’er tea soup could effectively maintain the stability of intestinal microecology and prevent the change of intestinal flora caused by DSS.LEfSe analysis showed that the Pu’er tea increased the richness of Bacteroidales,S24-7,Lactobacillus and Helicobacter,indicating that Pu’er tea soup may maintain intestinal microecological balance by increasing the number of probiotic strains.In summary,Pu’er tea could down-regulate the expression of B.cereus toxin gene and protect intestinal epithelial cells from damage caused by B.cereus.Pu’er tea can prevent DSS-induced colitis in mice,and it has important effects on protecting the abundance and diversity of intestinal flora,preventing the disturbance of intestinal flora,and maintaining the balance of intestinal flora. |
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