Guha Manisha, Singh Abhyudai, Butzin Nicholas C
Department of Biology and Microbiology; South Dakota State University; Brookings, SD, 57006; USA.
Electrical & Computer Engineering; University of Delaware; Newark, DE 19716; USA.
bioRxiv. 2024 Jun 7:2024.05.28.596288. doi: 10.1101/2024.05.28.596288.
Antibiotic resistance kills millions worldwide yearly. However, a major contributor to recurrent infections lies in a small fraction of bacterial cells, known as persisters. These cells are not inherently antibiotic-resistant, yet they lead to increased antibiotic usage, raising the risk of developing resistant progenies. In a bacterial population, individual cells exhibit considerable fluctuations in their gene expression levels despite being cultivated under identical, stable conditions. This variability in cell-to-cell characteristics (phenotypic diversity) within an isogenic population enables persister cells to withstand antibiotic exposure by entering a non-dividing state. We recently showed the existence of "primed cells" in . Primed cells are dividing cells prepared for antibiotic stress before encountering it and are more prone to form persisters. They also pass their "prepared state" down for several generations through epigenetic memory. Here, we show that primed cells are common among distant bacterial lineages, allowing for survival against antibiotics and other chemical stress, and form in different growth phases. They are also responsible for increased persister levels in transition and stationary phases compared to the log phase. We tested and showed that the Gram-positive bacterium , evolutionarily very distant from E. coli, forms primed cells and has a transient epigenetic memory that is maintained for 7 generations or more. We showed this using ciprofloxacin and the non-antibiotic chemical stress fluoride. It is well established that persister levels are higher in the stationary phase than in the log phase, and B. megaterium persisters levels are nearly identical from the early to late-log phase but are ~2-fold and ~4-fold higher in the transition and stationary phase, respectively. It was previously proposed that there are two distinct types of persisters: Type II forms in the log phase, while Type I forms in the stationary phase. However, we show that primed cells lead to increased persisters in the transition and stationary phase and found no evidence of Type I or II persisters with distant phenotypes. Overall, we have provided substantial evidence of the importance of primed cells and their transitory epigenetic memories to surviving stress.
抗生素耐药性每年在全球导致数百万人死亡。然而，反复感染的一个主要原因在于一小部分细菌细胞，即所谓的持留菌。这些细胞本身并非具有抗生素耐药性，但它们会导致抗生素使用量增加，从而提高产生耐药后代的风险。在一个细菌群体中，尽管细胞是在相同、稳定的条件下培养的，但单个细胞的基因表达水平仍会表现出相当大的波动。同基因群体中细胞间特征的这种变异性（表型多样性）使持留菌细胞能够通过进入非分裂状态来抵御抗生素暴露。我们最近发现了“预致敏细胞”的存在。预致敏细胞是在遇到抗生素应激之前就为其做好准备的正在分裂的细胞，并且更容易形成持留菌。它们还通过表观遗传记忆将其“准备状态”传递给几代细胞。在这里，我们表明预致敏细胞在远缘细菌谱系中很常见，能够在抗生素和其他化学应激下存活，并且在不同生长阶段形成。与对数期相比，它们还导致在过渡期和稳定期持留菌水平增加。我们测试并表明，与大肠杆菌在进化上相距甚远的革兰氏阳性菌巨大芽孢杆菌会形成预致敏细胞，并具有持续7代或更长时间的短暂表观遗传记忆。我们使用环丙沙星和非抗生素化学应激氟化物证明了这一点。众所周知，稳定期的持留菌水平高于对数期，巨大芽孢杆菌的持留菌水平在对数期早期到晚期几乎相同，但在过渡期和稳定期分别高出约2倍和约4倍。以前有人提出存在两种不同类型的持留菌：II型在对数期形成，而I型在稳定期形成。然而，我们表明预致敏细胞会导致过渡期和稳定期持留菌增加，并且没有发现具有不同表型的I型或II型持留菌的证据。总体而言，我们提供了大量证据证明预致敏细胞及其短暂的表观遗传记忆对于在应激中存活的重要性。
