Department of Laboratory Sciences, Gunma University Graduate School of Health Sciences, Maebashi, Japan.
Institute of Molecular Medicine, National Cheng Kung University, Tainan City, Taiwan; Center of Infectious Disease and Signaling Research, National Cheng Kung University, Tainan City, Taiwan.
Int J Med Microbiol. 2020 Jul;310(5):151431. doi: 10.1016/j.ijmm.2020.151431. Epub 2020 May 27.
A carbon dioxide-dependent small-colony variant of Escherichia coli SH4888 was isolated from blood cultures of a patient with cholangitis. To date, little is known regarding the molecular mechanisms leading to formation of carbon dioxide-dependent phenotypes in clinical isolates, but abnormalities in the carbonic anhydrase are thought to cause carbon dioxide autotrophy. In this study DNA sequence analysis of the carbonic anhydrase-encoding can locus in the carbon dioxide-dependent E. coli SH4888 revealed that the isolate had a 325-bp deletion spanning from the 3'-terminal region of can to the 3'-terminal region of hpt, which encodes a hypoxanthine phosphoribosyltransferase. To confirm that the carbon dioxide-dependent SCV phenotype of E. coli SH4888 was due to the can mutation, we performed a complementation test with a plasmid carrying an intact can that restored the normal phenotype. However, E. coli SH4888 had increased virulence compared to the can-complemented E. coli SH4888 in a murine infection model. In conclusion, these data confirm that impaired carbonic anhydrase function can cause a carbon dioxide-dependent SCV phenotype in E. coli SH4888 and provides a fitness advantage in terms of infection.
从一名胆管炎患者的血培养中分离出一株依赖二氧化碳的大肠杆菌 SH4888 小菌落变异体。迄今为止，对于导致临床分离株形成依赖二氧化碳表型的分子机制知之甚少，但碳酸酐酶的异常被认为会导致二氧化碳自养。在这项研究中，对依赖二氧化碳的大肠杆菌 SH4888 中碳酸酐酶编码基因 can 座的 DNA 序列分析表明，该分离株有一个 325bp 的缺失，跨越了 can 的 3'末端区域到编码次黄嘌呤磷酸核糖基转移酶的 hpt 的 3'末端区域。为了确认大肠杆菌 SH4888 的依赖二氧化碳的 SCV 表型是由于 can 突变，我们用携带完整 can 的质粒进行了互补测试，该质粒恢复了正常表型。然而，在小鼠感染模型中，与 can 互补的大肠杆菌 SH4888 相比，大肠杆菌 SH4888 的毒力增加。总之，这些数据证实，碳酸酐酶功能的受损可能导致大肠杆菌 SH4888 中出现依赖二氧化碳的 SCV 表型，并在感染方面提供了适应性优势。
