The dynamic balance of import and export of zinc in Escherichia coli suggests a heterogeneous population response to stress

Zinc is essential for life, but toxic in excess. Thus all cells must control their internal zinc concentration. We used a systems approach, alternating rounds of experiments and models, to further elucidate the zinc control systems in Escherichia coli. We measured the response to zinc of the main specific zinc import and export systems in the wild-type, and a series of deletion mutant strains. We interpreted these data with a detailed mathematical model and Bayesian model fitting routines. There are three key findings: first, that alternate, non-inducible importers and exporters are important. Second, that an internal zinc reservoir is essential for maintaining the internal zinc concentration. Third, our data fitting led us to propose that the cells mount a heterogeneous response to zinc: some respond effectively, while others die or stop growing. In a further round of experiments, we demonstrated lower viable cell counts in the mutant strain tested exposed to excess zinc, consistent with this hypothesis. A stochastic model simulation demonstrated considerable fluctuations in the cellular levels of the ZntA exporter protein, reinforcing this proposal. We hypothesize that maintaining population heterogeneity could be a bet-hedging response allowing a population of cells to survive in varied and fluctuating environments

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新聞記事読み上げ高齢者音声コーパス（S-JNAS）

1. 新聞記事文　155セット（1セット約100文）　※JNASと同様2. 音素バランス文　10セット（1セット約50文）　※JNASと同様3. 情報検索（レシピ，医療相談等）のタスク文　10セット（1セット50文）・学習用：1名あたり新聞記事文 1セット＋音素バランス文 2セット・テスト用：1名あたり新聞記事文 1 セット＋情報検索等のタスク文 2 セット1. Newspaper article sentences: 155 text sets (about 100 sentences per set), 16 176 sentences in total ※Same as JNAS2. ATR phonetically balanced sentences: 10 text sets (about 50 sentences per set), 503 sentences in total ※Same as JNAS3. Task sentences, such as information retrieval: 10 text sets (50 sentences per set), 500 sentences in total- Training set: 1 set of Newspaper sentences and 2 set of Task sentences per speaker- Test set: 1 set of Newspaper sentences and 2 set of Task sentences per speake