Studies of the productivity and maintenance of cell functions in the stationary-phase cells of bacteria

本研究旨在阐明大肠杆菌稳定期特异性功能的sigma^蛋白的结构与功能关系<38>，了解sigma^<38>蛋白在氨基酸生产细胞中的特性。得到的结果如下：（1）删除了区域4.2的sigma^的导数<38>比原始sigma^保留了更高的活性<38>，表明区域4.2具有调节活性的功能。(2)在产氨基酸的大肠杆菌细胞的培养物中（苏氨酸生产），sigma β蛋白的水平<38>在培养的前3至5小时迅速增加，然后在10- 20小时稳定在较低水平，并且之后再次增加。通过碳源向氨基酸的转化效率估计的氨基酸生产率在培养的20小时最高，然后下降。这些结果表明，可以通过监测细胞中sigma^蛋白的水平来指示高效生产氨基酸的临界时间<38>。

This research project was aimed to clarify the relationship between structure and function of sigma^<38> protein which functions specifically in the stationary phase of E.coli, and to know the properties of sigma^<38> protein in the amino acid-producing cells. The results obtained are as follows : (1) A derivative of sigma^<38> which has deleted the region 4.2 retained a higher activity than the original sigma^<38>, indicating that the region 4.2 has a function to moderate the activity. (2) In the culture of amino acid-producing E.coli cells (threonine production), the level of sigma^<38> protein increased rapidly in the first 3 to 5 hr cultivation, then settled down to a lower level at 10-20hr, and increased again afterward Amino acid productivity estimated by the conversion efficiency of carbon source to amino acid was highest at 20 hr cultivation and then decreased. These results indicate that the critical time for efficient production of amino acid can be pointed by monitoring the level of sigma^<38> protein in the cells.