乳酸乳球菌中质粒介导的寡肽转运系统缺失：牛奶凝固缓慢的另一个原因。
Loss of plasmid-mediated oligopeptide transport system in lactococci: another reason for slow milk coagulation.
作者信息
Yu W, Gillies K, Kondo J K, Broadbent J R, McKay L L
机构信息
Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota 55108, USA.
出版信息
Plasmid. 1996 May;35(3):145-55. doi: 10.1006/plas.1996.0017.
Fast milk-coagulating (Fmc+) strains of lactococci are known to segregate slow milk-coagulating (Fmc-) variants, which has been attributed to loss of proteinase (Prt) activity encoded by plasmid DNA. It was found that the Fmc- phenotype could also be due to loss of a plasmid encoding an oligopeptide permease (Opp) system. In Lactococcus lactis subsp. lactis (L. lactis) C2O, lactose metabolism (Lac) and Prt were linked to pJK550 and the Opp system to pJK430. In Lactococcus lactis subsp. cremoris SK11, known to possess Prt on a 78-kb plasmid, DNA sequence analysis of a 7.4-kb region from the Lac plasmid, pSK11L, revealed that it possessed the Opp system. The Lac plasmid in L. lactis C2 encoded both the Prt and Opp systems. Fmc- derivatives of L. lactis C2 were missing the prt genes and had Opp integrated into the chromosome, possibly due to transposition events. Growth studies showed the Opp systems were functional and, in combination with Prt, produced the Fmc+ phenotype.
已知乳酸乳球菌的快速凝乳（Fmc +）菌株会分离出慢速凝乳（Fmc -）变体，这被归因于质粒DNA编码的蛋白酶（Prt）活性丧失。研究发现，Fmc - 表型也可能是由于编码寡肽通透酶（Opp）系统的质粒缺失所致。在乳酸乳球菌乳酸亚种（L. lactis）C2O中，乳糖代谢（Lac）和Prt与pJK550相关联，而Opp系统与pJK430相关联。在乳酸乳球菌乳脂亚种（L. lactis）SK11中，已知其在一个78 kb的质粒上拥有Prt，对来自Lac质粒pSK11L的一个7.4 kb区域进行DNA序列分析后发现，它拥有Opp系统。乳酸乳球菌C2中的Lac质粒编码Prt和Opp系统。乳酸乳球菌C2的Fmc - 衍生物缺失prt基因，并且Opp整合到了染色体中，这可能是由于转座事件导致的。生长研究表明，Opp系统具有功能，并且与Prt结合后产生Fmc + 表型。
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