Real-time monitoring of the state of bacterial cultures is important in both experiment and biotechnology. Using Eh and sulfide sensors, we demonstrated that the abrupt reversible reduction in Eh (Eh jump), occurring during transition of E. coli from exponential growth to starvation and antibiotic-induced stresses, is the result of sulfide excretion from the cells. Changes in the potential of sensors had a two-phase mode. The potential reduced within 10–15 min and returned within 10–30 min. In the parental strain, maximum amplitudes of Eh jumps (ΔEh) were 25 ± 2 mV, 57 ± 6 mV and 36 ± 7 mV under isoleucine starvation, glucose depletion and ciprofloxacin exposure that corresponded to 43 ± 3 nM, 96 ± 5 nM and 140 ± 1 nM of sulfide, respectively. In the glutathione-deficient mutant (ΔgshA), ΔEh values and sulfide concentration increased 1.5–4 times compared to the parent. Stress-induced sulfide excretion occurred in the background of inhibition of growth and respiration and a decrease in the membrane potential. The formation of sulfide caused by cysteine desulfurization may be related with maintaining of cysteine homeostasis under conditions of slow metabolism. There was a close relationship between transmembrane fluxes of sulfide, cysteine and glutathione.

在实验和生物技术中，细菌培养状态的实时监控都很重要。使用Eh和硫化物传感器，我们证明了Eh的突然可逆减少（Eh跃迁）是在大肠杆菌从指数生长过渡到饥饿和抗生素诱导的应激过程中发生的，是细胞中硫化物排泄的结果。传感器的电势变化具有两相模式。电位在10–15分钟内减小，并在10–30分钟内返回。在亲本菌株中，在异亮氨酸饥饿，葡萄糖耗竭和环丙沙星暴露下，Eh跳跃的最大幅度（ΔEh）为25±2 mV，57±6 mV和36±7 mV，分别对应于43±3 nM，96±5 nM和分别为140±1 nM的硫化物。在缺乏谷胱甘肽的突变体（ΔgshA），与母体相比，ΔEh值和硫化物浓度增加了1.5–4倍。应力诱导的硫化物排泄发生在抑制生长和呼吸以及膜电位降低的背景下。半胱氨酸脱硫引起的硫化物的形成可能与在新陈代谢缓慢的情况下维持半胱氨酸稳态有关。硫化物，半胱氨酸和谷胱甘肽的跨膜通量之间存在密切关系。