Over the past decade, thousands of bacteriophage genomes have been sequenced and annotated. A striking observation from this work is that known structural features and functions cannot be assigned for >65% of the encoded proteins. One approach to begin experimentally elucidating the function of these uncharacterized gene products is genome-wide screening to identify phage genes that confer phenotypes of interest like inhibition of host growth. This study describes the results of a screen evaluating the effects of overexpressing each gene encoded by the temperate Cluster F1 mycobacteriophage Girr on the growth of the host bacterium Mycobacterium smegmatis. Overexpression of 29 of the 102 Girr genes (∼28% of the genome) resulted in mild to severe cytotoxicity. Of the 29 toxic genes described, 12 have no known function (NKF) and are predominately small proteins of <125 amino acids. Overexpression of the majority of these 12 cytotoxic NKF proteins resulted in moderate to severe growth reduction and represent novel antimicrobial products. The remaining 17 toxic genes have predicted functions, encoding products involved in phage structure, DNA replication/modification, DNA binding/gene regulation, or other enzymatic activity. Comparison of this dataset with prior genome-wide cytotoxicity screens of mycobacteriophages Waterfoul and Hammy reveals some common functional themes, though several of the predicted Girr functions associated with cytotoxicity in our report, including genes involved in lysogeny, have not been described previously. This study, completed as part of the HHMI-supported SEA-GENES project, highlights the power of parallel, genome-wide overexpression screens to identify novel interactions between phages and their hosts.

中文翻译：

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Cluster F1 分枝杆菌噬菌体 Girr 的全基因组细胞毒性筛选揭示了耻垢分枝杆菌生长的新型抑制剂

在过去的十年中，数千个噬菌体基因组已被测序和注释。这项工作的一个引人注目的观察结果是，已知的结构特征和功能不能分配给大于65％的编码蛋白质。开始通过实验阐明这些未表征的基因产物的功能的一种方法是进行全基因组筛选，以鉴定赋予感兴趣的表型（例如抑制宿主生长）的噬菌体基因。本研究描述了筛选结果，评估了温带 Cluster F1 分枝杆菌噬菌体 Girr 编码的每个基因的过度表达对宿主细菌耻垢分枝杆菌生长的影响。102 个 Girr 基因中的 29 个（约占基因组的 28%）过度表达会导致轻度至重度细胞毒性。在所描述的29个毒性基因中，12个没有已知的功能(NKF)并且主要是＜125个氨基酸的小蛋白质。这 12 种细胞毒性 NKF 蛋白中大多数的过度表达会导致中度至重度生长下降，是新型抗菌产品的代表。其余 17 个有毒基因具有预测功能，编码涉及噬菌体结构、DNA 复制/修饰、DNA 结合/基因调控或其他酶活性的产物。该数据集与先前的分枝杆菌噬菌体 Waterfoul 和 Hammy 的全基因组细胞毒性筛选的比较揭示了一些常见的功能主题，尽管我们报告中预测的与细胞毒性相关的几个 Girr 功能（包括参与溶源的基因）以前尚未描述过。这项研究是 HHMI 支持的 SEA-GENES 项目的一部分，强调了并行、全基因组过表达筛选的力量，以识别噬菌体与其宿主之间的新相互作用。