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自包头市售酸乳酪中分离出一株链球菌ＳＭ５２６，菌体多为长链球状，革兰氏染色阳性，抗酸染色阴性，兼性厌氧生长，最适生长温度为３０℃．无芽孢、荚膜及鞭毛，不运动．可从多种糖类产酸，但不产气．接触酶阴性，精氨酸双水解酶阳性，不液化明胶，还原石蕊牛奶并凝固．ＤＮＡ中Ｇ＋Ｃ为３８．５ｍｏｌ％．经鉴定，ＳＭ５２６菌株为乳酸链球菌（Ｓｔｒｅｐｔｏｃｏｃｃｕｓｌａｃｔｉｓ）．经用牛津杯琼脂扩散法检测ＳＭ５２６菌株发酵液，该菌能产生一种小分子活性肽——乳酸链球菌肽，它能抑制或杀死包括芽孢杆菌属、葡萄球菌属和梭菌属等在内的多种革兰氏阳性菌，但对革兰氏阴性菌、霉菌及酵母无效．以金黄色葡萄球菌（Ｓｔａｐｈｙｌｏｃｏｃｃｕｓａｕｒｅｕｓ）和枯草芽孢杆菌（Ｂａｃｉｌｕｓｓｕｂｔｉｌｉｓ）为指示菌株表明，乳酸链球菌肽对细菌的作用方式是杀菌
Streptococcus spp. SM526 was isolated from the yoghurt of Baotou head. Most of the cells were long-chain globular, Gram staining, negative acid-fast staining and facultative anaerobic growth. The optimum growth temperature was 30 ℃. No spores, capsular and flagella, no exercise. Acid from a variety of sugars, but not gas. Contact enzyme negative, arginine double hydrolase positive, no liquefaction gelatin, reduction of litmus milk and coagulation. G + C in DNA is 38.5 mol%. It has been identified that the SM526 strain is Streptococcus lactis. The fermented liquid of SM526 strain was tested by the method of Oxford Cup agar diffusion, which could produce a small molecule active peptide, nisin, which could inhibit or kill the fermentation of SM526 strain including Bacillus, Staphylococcus and Clostridium Within a variety of Gram-positive bacteria, but against Gram-negative bacteria, mold and yeast invalid. Staphylococcus aureus and Bacillus subtilis were used as indicator strains to show that the action of nisin on bacteria was bactericidal