Microbial strains with high genomic stability are particularly sought after for testing the quality of commercial microbiological products, such as biological media and antibiotics. Yet, using mutation–accumulation experiments and de novo assembled complete genomes based on Nanopore long-read sequencing, we find that the widely used quality-control strain Shewanella putrefaciens ATCC-8071, also a facultative pathogen, is a hypermutator, with a base-pair substitution mutation rate of 2.42 × 10−8 per nucleotide site per cell division, ∼146-fold greater than that of the wild-type strain CGMCC-1.6515. Using complementation experiments, we confirm that mutL dysfunction, which was a recent evolutionary event, is the cause for the high mutation rate of ATCC-8071. Further analyses also give insight into possible relationships between mutation and genome evolution in this important bacterium. This discovery of a well-known strain being a hypermutator necessitates screening the mutation rate of bacterial strains before any quality control or experiments.

中文翻译：

---

超突变表型的意外发现为质量控制菌株敲响了警钟

具有高基因组稳定性的微生物菌株特别适合用于测试商业微生物产品（例如生物培养基和抗生素）的质量。然而，通过使用突变积累实验和基于纳米孔长读长测序的从头组装完整基因组，我们发现广泛使用的质量控制菌株腐败希瓦氏菌 ATCC-8071（也是一种兼性病原体）是一种超突变子，具有碱基-每次细胞分裂每个核苷酸位点的配对替换突变率为 2.42 × 10−8，比野生型菌株 CGMCC-1.6515 高约 146 倍。通过互补实验，我们确认 mutL 功能障碍是最近的进化事件，是 ATCC-8071 高突变率的原因。进一步的分析还深入了解了这种重要细菌的突变和基因组进化之间可能的关系。众所周知的菌株是超突变体的发现需要在任何质量控制或实验之前筛选细菌菌株的突变率。