Hartline Christopher J, Zhang Ruixue, Zhang Fuzhong
Department of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, Saint Louis, MO, United States.
Division of Biology and Biomedical Sciences, Washington University in St. Louis, Saint Louis, MO, United States.
Front Microbiol. 2022 Mar 11;13:854272. doi: 10.3389/fmicb.2022.854272. eCollection 2022.
Nutrient shifts from glycolytic-to-gluconeogenic carbon sources can create large sub-populations of extremely antibiotic tolerant bacteria, called persisters. Positive feedback in central metabolism was believed to play a key role in the formation of persister cells. To examine whether positive feedback in nutrient transport can also support high persistence to β-lactams, we performed nutrient shifts for from gluconeogenic carbon sources to fatty acid (FA). We observed tri-phasic antibiotic killing kinetics characterized by a transient period of high antibiotic tolerance, followed by rapid killing then a slower persister-killing phase. The duration of transient tolerance (3-44 h) varies with pre-shift carbon source and correlates strongly with the time needed to accumulate the FA degradation enzyme FadD after the shift. Additionally, FadD accumulation time and thus transient tolerance time can be reduced by induction of the glyoxylate bypass prior to switching, highlighting that two interacting feedback loops simultaneously control the length of transient tolerance. Our results demonstrate that nutrient switches along with positive feedback are not sufficient to trigger persistence in a majority of the population but instead triggers only a temporary tolerance. Additionally, our results demonstrate that the pre-shift metabolic state determines the duration of transient tolerance and that supplying glyoxylate can facilitate antibiotic killing of bacteria.
营养物质从糖酵解碳源向糖异生碳源的转变会产生大量对抗生素具有极强耐受性的细菌亚群，即所谓的持留菌。人们认为中心代谢中的正反馈在持留菌细胞的形成中起关键作用。为了研究营养物质转运中的正反馈是否也能支持对β-内酰胺类抗生素的高耐受性，我们进行了从糖异生碳源到脂肪酸（FA）的营养物质转变实验。我们观察到了三相抗生素杀菌动力学，其特征是存在一个短暂的高抗生素耐受性时期，随后是快速杀菌，然后是较慢的持留菌杀灭阶段。短暂耐受性的持续时间（3 - 44小时）因转变前的碳源而异，并且与转变后积累FA降解酶FadD所需的时间密切相关。此外，在转换之前通过诱导乙醛酸旁路可以缩短FadD积累时间，从而缩短短暂耐受性时间，这突出表明两个相互作用的反馈回路同时控制着短暂耐受性的时长。我们的结果表明，营养物质转换以及正反馈不足以在大多数群体中触发持久性，而只会触发暂时的耐受性。此外，我们的结果表明，转变前的代谢状态决定了短暂耐受性的持续时间，并且提供乙醛酸可以促进抗生素对细菌的杀灭。
