Department of Microbiology, University of Oslo and Oslo University Hospital, Rikshospitalet, Oslo, Norway.
Department of Biology, Masaryk University, Kamenice 5/A7, 625 00, Brno, Czech Republic.
Sci Rep. 2020 Nov 10;10(1):19422. doi: 10.1038/s41598-020-76426-2.
Extracellular pH has been assumed to play little if any role in how bacteria respond to antibiotics and antibiotic resistance development. Here, we show that the intracellular pH of Escherichia coli equilibrates to the environmental pH following treatment with the DNA damaging antibiotic nalidixic acid. We demonstrate that this allows the environmental pH to influence the transcription of various DNA damage response genes and physiological processes such as filamentation. Using purified RecA and a known pH-sensitive mutant variant RecA K250R we show how pH can affect the biochemical activity of a protein central to control of the bacterial DNA damage response system. Finally, two different mutagenesis assays indicate that environmental pH affects antibiotic resistance development. Specifically, at environmental pH's greater than six we find that mutagenesis plays a significant role in producing antibiotic resistant mutants. At pH's less than or equal to 6 the genome appears more stable but extensive filamentation is observed, a phenomenon that has previously been linked to increased survival in the presence of macrophages.
细胞外 pH 值在细菌对抗生素的反应和抗生素耐药性发展中作用甚微，如果有的话。在这里，我们表明大肠杆菌的细胞内 pH 值在受到 DNA 损伤抗生素萘啶酸处理后与环境 pH 值达到平衡。我们证明，这使得环境 pH 值能够影响各种 DNA 损伤反应基因和生理过程（如丝状化）的转录。使用纯化的 RecA 和已知的 pH 敏感突变变体 RecA K250R，我们展示了 pH 值如何影响控制细菌 DNA 损伤反应系统的关键蛋白的生化活性。最后，两种不同的诱变测定表明环境 pH 值会影响抗生素耐药性的发展。具体来说，在环境 pH 值大于 6 时，我们发现诱变在产生抗生素耐药突变体方面起着重要作用。在 pH 值小于或等于 6 时，基因组似乎更稳定，但会观察到广泛的丝状化，这种现象以前与在巨噬细胞存在下增加生存能力有关。
