Mobile genetic elements, such as plasmids, phages, and transposons, are important sources for evolution of novel functions. In this study, we performed a large-scale screening of metagenomic phage libraries for their ability to suppress temperature-sensitivity in Salmonella enterica serovar Typhimurium strain LT2 mutants to examine how phage DNA could confer evolutionary novelty to bacteria. We identified an insert encoding 23 amino acids from a phage that when fused with a bacterial DNA-binding repressor protein (LacI) resulted in the formation of a chimeric protein that localized to the outer membrane. This relocalization of the chimeric protein resulted in increased membrane vesicle formation and an associated suppression of the temperature sensitivity of the bacterium. Both the host LacI protein and the extracellular 23-amino acid stretch are necessary for the generation of the novel phenotype. Furthermore, mutational analysis of the chimeric protein showed that although the native repressor function of the LacI protein is maintained in this chimeric structure, it is not necessary for the new function. Thus, our study demonstrates how a gene fusion between foreign DNA and bacterial DNA can generate novelty without compromising the native function of a given gene.

中文翻译：

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通过噬菌体DNA和细菌基因融合融合新功能。

流动的遗传元件，例如质粒，噬菌体和转座子，是新功能进化的重要来源。在这项研究中，我们进行了大规模筛选的宏基因组噬菌体文库，因为它们具有抑制肠炎沙门氏菌血清鼠伤寒沙门氏菌LT2突变体中温度敏感性的能力，以检查噬菌体DNA如何赋予细菌进化的新颖性。我们从噬菌体中鉴定出一个编码23个氨基酸的插入片段，该插入片段与细菌DNA结合阻遏蛋白（LacI）融合后，导致形成了定位于外膜的嵌合蛋白。嵌合蛋白的这种重新定位导致增加的膜囊泡形成和相关的细菌温度敏感性抑制。宿主LacI蛋白和细胞外23个氨基酸的延伸都是产生新表型所必需的。此外，对该嵌合蛋白的突变分析表明，尽管在该嵌合结构中保持了LacI蛋白的天然阻遏物功能，但对于新功能而言并不必要。因此，我们的研究证明了外源DNA与细菌DNA之间的基因融合如何在不损害给定基因的天然功能的情况下产生新颖性。