Molecular Mechanism of Viable but Nonculturable Bacteria

细菌学的建立是以琼脂平板纯培养技术的发展为基础的。虽然单个细胞很小，但在合适的条件下孵育后，细胞的存在被视为一个菌落。这项技术不仅使确认细胞的存在成为可能，而且也使对细胞进行计数成为可能。最终，人们开始认为，没有克隆意味着细胞的消失或死亡。很长一段时间以来，这一观点一直是细菌学几乎所有科学领域的标准。微生物生态学家是第一个认识到自然界中存在不可培养的细菌细胞的群体。他们发现，只有一小部分细菌可用标准方法培养，缺乏可培养性并不意味着没有活细胞。活的但不可培养(VNC)的概念是由Rita R.Colwell教授在1985年提出的。这种观点认为，细胞在保持某些代谢活动的同时，可能处于不可培养的状态。在一定条件下，这些细胞可能会恢复到正常状态，并开始显示出可培养能力。如果是这样的话，所有依赖于培养的诊断测试或检测方法都可能遗漏潜在有害微生物的存在。自该提案提出以来，据报道已有40多种细菌进入VNC状态。然而，这种生理状态很少在分子水平上得到准确的描述，这引起了人们对其真实状态的争议，本研究的目的是从分子水平上阐明其生理状态。

The establishment of bacteriology is based on the development of pure culture technique by using agar plates. Although individual cells are tiny, the presence of the cell is seen as a colony after incubation under the suitable condition. This technique had made it possible not only to confirm the presence but also to enumerate the cells. Eventually, it started to be regarded that no colony means the absence or death of the cells. This idea has been the standard for virtually all the scientific fields of bacteriology for long time.Microbial ecologists are the first group that had recognized the presence of non-culturable bacterial cells in nature. They found that only a small portion of bacteria were culturable by the standard method and the lack of culturability did not mean the absence of living cells.The concept of Viable but Nonculturable (VNC) was proposed in 1985 by Prof. Rita R.Colwell. This idea is that cells may fall in non-culturable state while keeping certain metabolic activities. Under certain condition, those cells may return to the normal condition and start to show the culturability. If this is the case, all the culture-dependent diagnostic tests or detection method may miss the presence of potentially harmful microorganisms. Since the proposal, more than 40 bacteria have been reported to fall into VNC states. However this physiological state has seldom been precisely described at molecular level, which causes controversial discussions on its real state.The purpose of this research was to clarify its physiological state at molecular level.