Characterization of the two-component abortive phage infection mechanism AbiT from Lactococcus lactis
Characterization of the two-component abortive phage infection mechanism AbiT from Lactococcus lactis
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DOI：
10.1128/jb.184.22.6325-6332.2002
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发表时间：
2002-11-01
影响因子：
3.2
通讯作者：
Moineau, S
中科院分区：
文献类型：
--
作者：
Bouchard, JD;Dion, E;Moineau, S
在发酵乳制品的生产过程中，感染乳酸乳球菌的有毒噬菌体可以延迟或停止牛奶酸化过程。解决这一生物学问题的一个方法是将天然噬菌体屏障引入乳制品工业使用的菌株中。一个这样的障碍被称为流产感染（Abi），并导致细胞过早死亡，没有或很少有噬菌体后代。在这里，我们描述了一个新的阿比特龙机制的分离和表征的质粒pED 1编码的L。乳酸菌。该系统由两个组成型共转录基因组成，分别编码127和213个氨基酸的推定蛋白质，分别命名为AbiTi和AbiTii。定点突变表明AbiTi的C-末端的疏水区域对于抗噬菌体表型是必不可少的。AbiT系统对936和P335种类的噬菌斑是有效的（噬斑形成效率在10（-5）和10（-7）之间），并且导致形成感染中心的效率降低20倍以及爆发大小降低10- 12倍。通过增加质粒拷贝数可以提高其抗噬菌体活性，但改变AbiTi和AbiTii的内在比例对抗噬菌体活性没有很大影响。通过DNA复制、基因表达和电子显微镜对细胞内噬菌体感染过程的监测以及通过基因组作图对噬菌体突变体的研究表明，ANT可能在噬菌体裂解周期的后期起作用。
During the production of fermented dairy products, virulent bacteriophages infecting Lactococcus lactis can delay or stop the milk acidification process. A solution to this biological problem consists of introducing natural phage barriers into the strains used by the dairy industry. One such hurdle is called abortive infection (Abi) and causes premature cell death with no or little phage progeny. Here, we describe the isolation and characterization of a novel Abi mechanism encoded by plasmid pED1 from L. lactis. The system is composed of two constitutively cotranscribed genes encoding putative proteins of 127 and 213 amino acids, named AbiTi and AbiTii, respectively. Site-directed mutagenesis indicated that a hydrophobic region at the C-terminal extremity of AbiTi is essential to the antiphage phenotype. The AbiT system is effective against phages of the 936 and P335 species (efficiency of plaquing between 10(-5) and 10(-7)) and causes a 20-fold reduction in the efficiency to form centers of infection as well as a 10- to 12-fold reduction in the burst size. Its efficacy could be improved by raising the plasmid copy number, but changing the intrinsic ratio of AbiTi and AbiTii did not greatly affect the antiphage activity. The monitoring of the intracellular phage infection process by DNA replication, gene expression, and electron microscopy as well as the study of phage mutants by genome mapping indicated that ANT is likely to act at a later stage of the phage lytic cycle.