Depletion of pre-16S rRNA in starved Escherichia coli cells
Depletion of pre-16S rRNA in starved Escherichia coli cells
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DOI：
10.1128/jb.179.14.4457-4463.1997
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发表时间：
1997-07-01
影响因子：
3.2
通讯作者：
Brabant, WH
中科院分区：
文献类型：
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作者：
Cangelosi, GA;Brabant, WH
对rRNA合成中间体（pre-rRNA）进行特异性杂交分析可能有助于监测复杂自然系统中单个微生物物种的生长活性。这种可能性取决于这样一个假设：微生物细胞中的rRNA加工在生长和pre-rRNA合成停止后仍在继续，导致pre-rRNA池的流失。在许多真核细胞中并非如此，但对细菌的情况了解较少。因此，我们使用DNA探针来测量大肠杆菌生长状态转变期间的稳态细胞前16s rRNA池。当细胞在富培养基上进入固定期时，Pre-16S rRNA无法检测到，当恢复良好的生长条件时，补充Pre-16S rRNA。这些波动比成熟16S rRNA池中同时发生的波动要大得多。pre-16S rRNA缺失的程度取决于限制生长的环境。这在缺乏碳能量的细胞中比在缺乏氮的细胞或用能量解耦剂处理的细胞中更为明显。在转录抑制剂利福平的存在下，碳能量匮乏的细胞和氮匮乏的细胞中pre-16S rRNA的消耗率相似，这表明这些条件之间的差异主要存在于pre-rRNA合成水平上。氯霉素抑制rRNA成熟的最后步骤，在所有条件下都停止了16s前rRNA的消耗。数据显示，大肠杆菌细胞在生长后继续加工pre-rRNA，而rrn操纵子转录停止，导致pre-rRNA池流出。这支持了使用pre-rRNA靶向探针来监测自然系统中细菌生长的可行性，需要注意的是，pre-rRNA消耗的模式会随着限制生长的条件而变化。
Specific hybridization assays for intermediates in rRNA synthesis (pre-rRNA) may become useful for monitoring the growth activity of individual microbial species in complex natural systems. This possibility depends upon the assumption that rRNA processing in microbial cells continues after growth and pre-rRNA synthesis cease, resulting in drainage of the pre-rRNA pool. This is not the case in many eukaryotic cells, but less is known about the situation in bacteria. Therefore, we used DNA probes to measure steady-state cellular pre-16S rRNA pools during growth state transitions in Escherichia coli. Pre-16S rRNA became undetectable when cells entered the stationary phase on rich medium and was replenished upon restoration of favorable growth conditions. These fluctuations were of much greater magnitude than concurrent fluctuations in the mature 16S rRNA pool. The extent of pre-16S rRNA depletion depended upon the circumstances limiting growth. It was significantly more pronounced in carbon-energy-starved cells than in nitrogen-starved cells or in cells treated with energy uncouplers. In the presence of the transcriptional inhibitor rifampin, rates of pre-16S rRNA depletion in carbon-energy-starved cells and nitrogen-starved cells were similar, suggesting that the difference between these conditions resides primarily at the level of pre-rRNA synthesis. Chloramphenicol, which inhibits the final steps in rRNA maturation, halted pre-16S rRNA depletion under all conditions. The data show that E. coli cells continue to process pre-rRNA after growth and rrn operon transcription cease, leading to drainage of the pre-rRNA pool. This supports the feasibility of using pre-rRNA-targeted probes to monitor bacterial growth in natural systems, with the caveat that patterns of pre-rRNA depletion vary with the conditions limiting growth.