Relationship between changes in buoyant density and formation of new sites of cell wall growth in cultures of streptococci (Enterococcus hirae ATCC 9790) undergoing a nutritional shift-up.
Relationship between changes in buoyant density and formation of new sites of cell wall growth in cultures of streptococci (Enterococcus hirae ATCC 9790) undergoing a nutritional shift-up.
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经历营养转变的链球菌（海拉肠球菌 ATCC 9790）培养物中浮力密度变化与新细胞壁生长位点形成之间的关系。
DOI：
10.1128/jb.172.8.4415-4419.1990
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发表时间：
1990
影响因子：
3.2
通讯作者：
Bylund,J
中科院分区：
文献类型：
--
作者：
Higgins,ML;Haines,M;Whalen,M;Glaser,D;Bylund,J
当培养基谷氨酸浓度从20微克/毫升增加到300微克/毫升时，在9分钟内质量倍增时间从85分钟减少到45分钟，但在30~40分钟后仍未恢复平衡生长。在不平衡生长时期，核糖核酸和蛋白质的合成比肽聚糖的合成进行得更快，浮力密度从约1.1024 g/ml增加到1.1075 g/ml，新的细胞壁生长部位的形成速度在新的生长速度之上短暂加速。当作为细胞大小的函数进行研究时，所有培养物在细胞分离周围显示浮力密度降低，随着细胞大小的增加而增加，然后当细胞达到大体积时停滞不前。上移后浮力密度随细胞大小的变化有较大幅度的增加，最大值出现在上移后15-20分钟，此时新部位的形成速度也最快。在上移15分钟后进行电子显微镜检查的细胞群体中，随着旧位置接近两极的大小，浮力密度和具有新位置的细胞的频率增加。这些数据与一个模型一致，该模型认为当细胞表面生长慢于细胞质生长时，浮力密度在细胞周期的末期增加。内部和外部增长速度的差异越大，浮力密度的增加就越大，新的站点就会更频繁地被启动。
When the glutamate concentration of cultures of Enterococcus hirae was raised from 20 to 300 micrograms/ml, the mass doubling time decreased from ca. 85 to 45 min in 9 min, but balanced growth was not reestablished for 30 to 40 min. During the unbalanced period of growth, RNA and protein synthesis proceeded more rapidly than did peptidoglycan synthesis, buoyant density increased from ca. 1.1024 to 1.1075 g/ml, and the rate of formation of new cell wall growth sites transitorily accelerated above the new growth rate. When studied as a function of cell size, all cultures showed buoyant density to decrease around cell separation, increase as cells increased in size, and then plateau when cells reached large volumes. Greater increases in buoyant density as a function of cell size were seen after shift-up, with the greatest increases observed at 15 to 20 min after shift-up, when the rate of formation of new sites was also maximal. In a population of cells examined by electron microscopy 15 min after shift-up, buoyant density and the frequency of cells with new sites increased as old sites approached the size of two poles. These data were consistent with a model whereby buoyant density increases in the terminal stages of the cell cycle when the surface grows slower than the cytoplasm. The greater the difference in the rates of inside to outside growth, the greater the increase in buoyant density and the more frequently new sites will be initiated.