پریسا فتحی رضایی

BACKGROUND AND OBJECTIVES The word probiotic is derived from the Greek word probios, meaning for life. This term was first used by Stillwell and Lilley in 1965 for microorganisms that have a positive effect on the growth and balance of intestinal microbial flora. Dairy products are very favorable carriers for probiotics. Probiotics are found in dairy products such as milk, yogurt, cheese, ice cream, buttermilk, and sour cream. In addition to live bacteria, probiotic yogurts provide the host with nutrients such as biological peptides and calcium. Lactic acid bacteria are among the most important probiotics, the most famous of which are Bifidobacterium and Lactobacillus genera. MATERIALS AND METHODS In this study, M09 isolate was isolated from traditional yogurt samples of Maragheh. After purification, preliminary tests were conducted to evaluate probiotic characteristics such as gram, catalase, hemolysis, oxidase, acid and bile salts resistance tests and biochemical and microbial tests including sugar fermentation, SIM, nitrate reduction, antibiotic resistance and antimicrobial. In order to the molecular identification of the isolate, DNA was extracted, 16S rRNA gene amplified by PCR, PCR result visualized using gel electrophoresis. Then, the phylogenetic tree of the isolate was constructed by neighbor-joining method via BioEdit (version 7.2) and MEGA (version 7) softwares. RESULTS AND DISCUSSION According to the biochemical, phenotypic and microbial findings, the isolate was gram-positive bacteria, negative results for catalase and oxidase tests, resistance to bile salts and acidic pH, absence of hemolysis, resistant to antibiotics, able to sugar fermentation and nitrate reduction. The molecular analysis results showed that the isolate 99% similar to Limosilactobacillus fermentum (CECT 562(T) AJ575812) in terms of genetic affinity and the nucleotide sequence of the isolate was registered in the gene bank with the accession number (OQ568196). CONCLUSION The isolated