| In this paper, we screened Bifidobacteria possessing the ability to adhere to intestinal epithelial cells as the tested strains. Their biological characteristics, adherence functions, antimicrobial properties, antibiotic susceptibility and plasmid DNA were also preliminarily investigated in the hope of obtaining some valuable knowledge that can be referred to in the development of food-grade Bifidobacteria starter and microecologics.This paper mainly focused on the following aspects:1. Twenty-three bifidobacterial strains were tested for surface hydrophobicity with MATH method, this paper also involved testing on the adherence of the bacteria to intestinal epithelial cells Caco-2 in vitro at the same time. Certain correlation was observed between surface hydrophobicity and adherence ability. Strain H-10 and I-6 showed high adherence to the epithelial cells. The present study provided a method for preliminary screening of Bifidobacteria possessing high adherence to intestinal epithelial cells.2. According to its morphology, together with physiologic and biochemical tests, the strain H-10 and O-6 were identified as Bifidobacterium asteroides and Bifidobacterium pseudocatenulatum respectively. B. asteroides H-10 and B. pseudocatenulatum I-6 both growed better in modified MRS broth than MRS and PTYG broth.Their optimal temperature and initial pH were 37℃ and 7.0. They entered logarithm phase after 2 hours of inoculation, and stability phase after 12 hours. Their optimal inoculation quantity for growth were 3% and 2%, respectively.3. The adherence characteristics, adhesin, receptor and the effect of differently-killed bacteria on adhesion were studied in this paper. This adhesion of strain H-10 and I-6 to to cell line Caco-2 were influenced by bacteria concentration and the time that it interacted with Caco-2 cells.Bacteria of the stability phase and low pH also help to improve the adherence. The adhesin mainly existed in the supernatant of the cultures.When bacteria tested were treated with trypsin or BSA, their performance descended greatly. This indicated that the protein secreted and transported to its cell surface by these two strains might be the main ingredient of adhesin, and LTA may be involved with this interaction. No significant difference was observed when treated with EPS.When Caco-2 cells were treated with trypsin and sodium periodate before interaction with the Bifidobacteria, the adherence index significantly went down, showing the adhesin receptor of cell line Caco-2 may be composed by glycoprotein. Several saccharides were added during the interaction. Lactose, rhamnose and mannose could depress the adhesion performances. It indicated that the composition of the receptor for bacteria tested may be involved with these three saccharides.when 24-hour culture of strain H-10 and I-6 were killed by heating at 80℃ for 30min and exposition in ultraviolet radiation for 30min respectively before acting with the cells, their adherence significantly descended, sindicating that the adhesin of these two strains were heat-sensitive and radiation-sensitive.4. The inhibitory effects of Strain H-10 and 1-6 on enteropathogen Staphylococcus aureus and Escherichia coli were demonstrated by simultaneous incubation and antimicrobial testing. These antibacterial activities were mainly induced by organic acids produced by Bifldobacteria. The release of LDH of Caco-2 cells which were differently treated with Bifldobacteria and enteropathogen,suggested that the adherence of Bifldobacteria were essentially different with those of enteropathogen, and the adhesion of strain H-10 and 1-6 could prevent the harmful effect of Staphylococcus aureus and Escherichia coli on Caco-2 cells.5. With Staphylococcus aureus ATCC 25923 as the control bacterium, the antibiotic susceptibility of 10 adhesive strains were tested by the agar diffusion method. Twelve groups of antibiotics, thirty-eight kinds in total, were involved in the testing. Strain H-10 showed its antibiotic susceptibili...
|
PDF Full Text Request