Salmonella typhimurium apparently perceives external nitrogen limitation as internal glutamine limitation
Salmonella typhimurium apparently perceives external nitrogen limitation as internal glutamine limitation
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DOI：
10.1006/jmbi.1996.0342
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发表时间：
1996-06-21
影响因子：
5.6
通讯作者：
Kustu, S
中科院分区：
文献类型：
--
作者：
Ikeda, TP;Shauger, AE;Kustu, S
氮的同化只需要合成两个中间产物，谷氨酸和谷氨酰胺，其他化合物通过二次转移从其中获得氮。我们测量了外部氮限制或充足条件下鼠伤寒沙门氏菌中谷氨酸和谷氨酰胺的内部傻瓜大小。当生长因氮限制而减慢时，谷氨酰胺库降低了10倍，而谷氨酸库仍然很高。谷氨酰胺库的减少是普遍的，在分批培养中以各种限制性氮源观察到，在连续培养中以氨（最佳氮源）作为限制性营养素观察到。唯一的氮源，给出了不一致的结果是丙氨酸，我们提出的证据表明，丙氨酸具有抑制作用，超出简单的氮限制。对氮同化作用发生改变的突变株的研究表明，在氮限制条件下野生型菌株中观察到的谷氨酰胺库的减少可能足以解释生长缓慢，并且可能是生长缓慢的原因。因此，我们假设外部氮限制首先被沙门氏菌感知为其内部谷氨酰胺库的下降。(C)1996年学术出版社
Assimilation of nitrogen requires the synthesis of only two central intermediates, glutamate and glutamine, from which other compounds derive nitrogen by secondary transfers. We measured the internal Fool sizes of glutamate and glutamine in Salmonella typhimurium under conditions of external nitrogen limitation or sufficiency When growth was slowed by nitrogen limitation, the glutamine pool was lower by a factor of up to 10, wheras the glutamate pool remained high. The decrease in the glutamine pool was general in nature, being seen with various limiting nitrogen sources in batch culture and with ammonia, the optimal nitrogen source, as the limiting nutrient in continuous culture. The only nitrogen source that gave discordant results was alanine, and we present evidence that alanine has inhibitory effects which extend beyond simple nitrogen limitation. Studies with mutant strains having altered nitrogen assimilation indicated that the decreases in the glutamine pool observed in the wild-type strain under nitrogen-limiting conditions were probably sufficient to account for slow growth and were likely to be responsible for slow growth. Hence we postulate that external nitrogen limitation is first perceived by Salmonella as a drop in its internal glutamine pool. (C) 1996 Academic Press Limited