Department of Biological Sciences, Lehigh University, Bethlehem, PA 18015, USA.
Memsel, Inc., 3500 Camp Bowie Blvd., Fort Worth, TX 76107, USA.
G3 (Bethesda). 2023 Dec 6;13(12). doi: 10.1093/g3journal/jkad210.
Comparative analyses of mycobacteriophage genomes reveals extensive genetic diversity in genome organization and gene content, contributing to widespread mosaicism. We previously reported that the prophage of mycobacteriophage Butters (cluster N) provides defense against infection by Island3 (subcluster I1). To explore the anti-Island3 defense mechanism, we attempted to isolate Island3 defense escape mutants on a Butters lysogen, but only uncovered phages with recombinant genomes comprised of regions of Butters and Island3 arranged from left arm to right arm as Butters-Island3-Butters (BIBs). Recombination occurs within two distinct homologous regions that encompass lysin A, lysin B, and holin genes in one segment, and RecE and RecT genes in the other. Structural genes of mosaic BIB genomes are contributed by Butters while the immunity cassette is derived from Island3. Consequently, BIBs are morphologically identical to Butters (as shown by transmission electron microscopy) but are homoimmune with Island3. Recombinant phages overcome antiphage defense and silencing of the lytic cycle. We leverage this observation to propose a stratagem to generate novel phages for potential therapeutic use.
比较分枝杆菌噬菌体基因组的分析揭示了其基因组组织和基因组成的广泛遗传多样性，导致了广泛的镶嵌现象。我们之前曾报道过分枝杆菌噬菌体 Butters（簇 N）的前噬菌体提供了针对 Island3（亚簇 I1）感染的防御。为了探索抗 Island3 的防御机制，我们试图在 Butters 溶原菌上分离 Island3 防御逃逸突变体，但仅发现了重组基因组的噬菌体，这些噬菌体的基因组由从左臂到右臂排列的 Butters 和 Island3 区域组成，称为 Butters-Island3-Butters（BIB）。重组发生在两个不同的同源区域内，这两个区域包含一个片段中的溶菌酶 A、溶菌酶 B 和 holin 基因，以及另一个片段中的 RecE 和 RecT 基因。镶嵌 BIB 基因组的结构基因来自 Butters，而免疫盒则来自 Island3。因此，BIB 在形态上与 Butters 相同（通过透射电子显微镜显示），但对 Island3 具有同源免疫性。重组噬菌体克服了抗噬菌体防御和溶菌周期的沉默。我们利用这一观察结果提出了一种策略，以生成用于潜在治疗用途的新型噬菌体。
