产抑菌素菌株SM-A的分离和鉴定

THE ISOLATION AND IDENTIFICATION OF ANTIMICROBIAL-PRODUCING STRAIN SM-A

自市售酸乳酪中分离到一株乳球菌SM-A菌株。该菌株产生的抑菌素能抑制或杀死芽孢杆菌、葡萄球菌、微球菌、链球菌、棒杆菌和梭菌等革兰氏阳性细菌,但对革兰氏阴性细菌、霉菌和酵母无效。SM-A菌株多为链球状,也有成对存在。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32℃,不形成芽孢,无荚膜和鞭毛,不运动;可从多种糖类产酸,但不产气;接触酶、苯丙氨酸脱氨酶和酪氨酸脱羧酶均为阴性,精氨酸双水解酶阳性;不液化明胶,还原石蕊牛奶并胨化,生长温度范围10～43℃,DNA中G+Cmol为36.4％。经鉴定,SM-A菌株为乳酸乳球菌乳酸亚种(Lactococcus lactis subsp.lactis)。

One strain of Lactococcus, SM-A, was isolated from a commercial yoghurt. It can produce an antimicrobial with activity upon various Gram-positive bacteria including Bacillus, Staphylococcus, Micrococcus, Streptococcus, Clostridium and Corynebacterium. But it has no activity on Gram-negative bacteria, fungi or yeasts. The strain is Gram-positive, acid-fast negative, nonsporing, facultative anaerobic and without flagellium and capsula. The ovoid cells of the strain are elongated in the direction of the chain, 0.75- 1.25μm in diameter and mostly in chains or pairs. The optimum temperature for growth is 32℃. Many kinds of carbohydrates can be utilized for acid production, but no gas is produced. Gelatin can not be liquefied. Catalase, phenylalanine deaminase and tyrosine decarboxylase are all negative. Arginine dihydralase is positive. Litmus milk is reduced and peptonized. Growth is found in the range of 10℃to 43℃. G+C content in DNA is 36. 4 mol% (Tm). Therefore, according to the references, strain SM-A is identified as Lactococcus lactis subsp. lactis.