Isolation And Identification Of Lactic Acid Bacteria From Breast Milk And Identification Of New Species Of Streptococcus

Breast milk is rich in nutrients and complex microbial flora,which is not only the main source of nutrients for infants,but also an important factor affecting the formation of neonatal intestinal flora.Xinjiang Uygur Autonomous Region has different geographical conditions,climatic environment and national characteristics,leading to the unique food culture of local residents,thus affecting the microbial flora structure and gene function in breast milk.In this paper,the diversity of lactic acid bacteria in Xinjiang's breast milk was studied by traditional pure culture method and 16 S r RNA gene sequence identification technology.The new species of Streptococcus was found,using morphology,physiology,biochemical analysis,phylogenetic analysis and genomic data analysis,Streptococcus could not be identified accurately and its homology was very low compared with the existing model strain.The suspected new species of Streptococcus were identified.The results were shown below:1.71 strains of lactic acid bacteria were isolated and identified from six samples of breast milk.Through 16 S r RNA gene sequence alignment,all strains belonged to 6 genera and 12 species,among which Streptococcus salivariu was the dominant species in breast milk samples,accounting for 38.03% of the total strains.2.The strain IMAU99161 couldn't be identified by the existing methods,so it was classified as a suspected new bacterial species of Streptococcus,which is Gram-positive bacteria with negative VP test and negative catalase.The morphology of cells is single spherical and arranged in short chain.Microscopic morphology showed that single bacteria were spherical or oval,with a diameter of about 0.4-1.0?m,arranged in double or short chains with different lengths,and there was no hemolysis on blood agar plate.The strain IMAU99161 can ferment D-fructose,mannitol and N-acetylglucosamine,but does not ferment xylitol and fucose.The main fatty acids contained in strain IMAU99161 were(>5%): C16:0,C18:1?7c,C20:1?9c and C18:0.3.The strain IMAU99161 have a total genome length of 2,064,779 bp,The content of G+C mol% in DNA was 41.6,encoding 1,941 genes and carrying 59 RNA.A total of 1022 genes correspond to KEGG database annotation results,which are distributed in 181 metabolic pathways and have 10 possible virulence-related genes,mainly including proteins and polysaccharides.The new species IMAU99161 has DNA-DNA hybridization similarities of 63.8% and 34.1% respectively with its model strains Streptococcus lactarius and Streptococcus parasanguinis,and the ANI index of IMAU99161 and other reference strains belonging to Streptococcus are lower than 87.16%.Therefore,the new strain of Streptococcus imauus was named,and the strain IMAU99161 was identified as its model strain,which was deposited in China General Microbiological Collection Center(CGMCC)and Korea National Institute of Agricultural Biotechnology(KACC)respectively,and obtained the corresponding strain deposit numbers of CGMCC18474 and KACC21943.4.A new strain of streptococcus was studied for its antibacterial properties and the characteristics of fermented milk.It can be seen that IMAU99161 has a certain inhibitory ability on pathogenic bacteria.IMAU99161 has an inhibition zone of 12 mm against Actinobacillus and IMAU99161 has an inhibition circle of 16 mm against Porphyromonas gingivalis.It takes about 16 hours for the strain IMAU99161 to reach the end of fermentation,at this time,the p H of fermented milk is 4.51,the titration acidity is 98.48 °T,the water holding capacity is 57.40%,and the viscosity is 852.00 m Pa·s.In this paper,lactic acid bacteria in breast milk samples were isolated and identified,and it was found that there were a large number of lactic acid bacteria resources in breast milk in Xinjiang,and streptococcus was the dominant flora in breast milk.A new species of Streptococcus was found in these isolates.The results of this paper not only help to broaden our research horizon on the diversity of lactic acid bacteria in breast milk,but also provide broad development and application prospects for lactic acid bacteria resource pool.