Role of Alarmones in The Protection of Escherichia coli Against Stress

摘要: Escherichia coli has evolved in environments which may commonly be acidic and thus developed adaptive mechanisms to minimise acid-induced damage. It previously been observed that adapted bacteria moderately conditions can grow media considerably below their optimum growth pH. To explain this phenomenon, a hypothesis suggested diffusible molecules (alarmones) serve as early warning systems of was proposed. Alarmones are thought produced upon exposure mildly-acidic conditions. They then diffuse the environment elicit protective response against acid recipient cells. The activity those putative alarmones lethal investigated. main aim project is determine mode action at molecular level. Preliminary experiments confirmed resistance conferred by populations E. C600. stability different temperatures following proteinase K treatment Moreover, investigations into whether autoinducer-2 (AI-2) increase percentage persisters an population were undertaken. Subsequently, microarray analyses both alarmone-induced non-induced cultures performed reveal genes induced alarmones. proteomic studies using two-dimensional gel electrophoresis conducted proteins Supernatants from statistically significant protection (p<0.01) on (pH3). inactivated heat (60oC) K. assay revealed not AI-2 molecules. In addition, did persisters. order elucidate potential for alarmone-mediated protection, genomic expression protein induction cells analysis electrophoresis, respectively, performed. Two-dimensional transduced indicated around 13 alarmone-protected Mass-spectrometric these alarmone-inducible include stress chaperone HdeB DNA-binding transcriptional dual regulator, H-NS plays important role adaptation. Microarray 671 open reading frames (ORFs) significantly differentially expressed between control (p<0.05). 508 ORFs upregulated including 10 related acid-resistance 36 multidrug efflux system whereas 163 downregulated. releases signalling compounds mediate adaptation data show two fitness island (hdeB hdeD) three encode antiporters amino-acid-dependent (gadC, adiC cadB) among genes. This work confirms there communication bacterial general messages amongst C600 particular presence stress.