Abstract: A lactic acid bacteria strain,M-2,producing inhibitory activity substance,is isolated from a Inner Mongolia traditional cheese.The bacteriocin shows a strong antimicrobial activity against most of the tested spoilage and food-borne pathogenic bacteria, such as Listeria monocylogenes,Staphylococcus aureus and so on.After eliminating some interference factors such as the organic acids,hydrogen peroxides and so on,the antimicrobial activity still exisits.By ammonium sulphate precipitation,dialysis and concentration,this substance is inactivated when treated with proteinase K.M-2 is identified Enterococcusfaecium on the base of physiological and biochemical characteristics and 16S rRNA gene sequences.The sequence fragment of 1675 bp 16S ribosomal RNA is amplified from total DNA of strain M-2 by PCR.The sequence analysis is completed by the application of BLAST on the websites of NCBI and the phylogenetic tree is drawn with Bioedit 7.0 with treedrawing.The results show that M-2 shares 99.87 % 16S rRNA sequence homology with Enterococcusfaecium strain SF.In phylogenetic framework of bacteria classification. strain M-2 belongs to Enterococcusfaeciurn.According to classification of bacteriocins,the bacterioncin belongs to classⅡa bacteriocins.

Key words: LAB, class IIa bacteriocin, Enterococcus faecium, 16SrRNA, identification