Leavitt R W, Braithwaite C, Jensen M M
Department of Microbiology, Brigham Young University, Provo, UT 84602, USA.
Avian Dis. 1997 Jul-Sep;41(3):568-77.
Escherichia coli strain 38, an isolate from turkeys, has been previously shown to produce one or more broad-spectrum bacteriocins against other related enteric bacteria. Using a collection of E. coli strains that synthesized well-characterized colicins or microcins, along with a set of colicin/microcin-insensitive mutants, we were able to classify the bacteriocins produced by strain 38. We determined that strain 38 produced a microcin (microcin C38) and a colicin (colicin V38) and that the amount of microcin C38 depended on the type of media on which it was grown. Escherichia coli strain 38 was found to have cross-immunity with the microcin C7-producing strain MC4100 and with the colicin V-producing strain 4674. OmpF mutant cells were found to be insensitive to microcin C38, whereas colicin V38 was not active on cells that had a cir mutation. Both microcin C38 and colicin V38 were inactivated by proteases. Microcin C38 was stable at extremes of pH (pH 1.5 and pH 13) and heat (10 min at 98 C) conditions, whereas colicin V38 was not. In addition, microcin C38 was found to be active against a broader spectrum of gram-negative bacteria than was colicin V38.
大肠杆菌38菌株是从火鸡中分离出来的，此前已证明它能产生一种或多种针对其他相关肠道细菌的广谱细菌素。我们利用一组合成了特征明确的大肠杆菌素或微菌素的大肠杆菌菌株，以及一组对大肠杆菌素/微菌素不敏感的突变体，对38菌株产生的细菌素进行了分类。我们确定38菌株产生了一种微菌素（微菌素C38）和一种大肠杆菌素（大肠杆菌素V38），并且微菌素C38的产量取决于其生长的培养基类型。发现大肠杆菌38菌株与产生微菌素C7的MC4100菌株以及产生大肠杆菌素V的4674菌株具有交叉免疫性。发现OmpF突变细胞对微菌素C38不敏感，而大肠杆菌素V38对具有cir突变的细胞没有活性。微菌素C38和大肠杆菌素V38都能被蛋白酶灭活。微菌素C38在极端pH值（pH 1.5和pH 13）和高温（98℃下10分钟）条件下稳定，而大肠杆菌素V38则不然。此外，发现微菌素C38比大肠杆菌素V38对更广泛的革兰氏阴性菌具有活性。
