... the PII protein and for the N-terminal domain of NtrC have allowed further advances towards the aim of being able to describe at the atomic level the signal transduction process which communicates the cellular nitrogen stratus to the transcriptional machinery. The activity of the Ntr regulon alters as a result of the nitrogen supply which is available to bacteria. The genes that are encoded by the Ntr regulon are affected by the supply of ammonia that the bacterial cell has. In this way, the activation of these genes within the Ntr regulon are regulated by the supply of ammonia (and therefore acts to sense these levels of ammonia). There are many different nitrogen sources, organic and inorganic, that can be taken up by bacteria, including nitrate, nitrogen gas or urea, but whatever the source, it will be converted to ammonia. This ammonia may then be assimilated via the glutamate synthetase ...

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