Control of cell division in Escherichia coli: regulation of transcription of ftsQA involves both rpoS and SdiA-mediated autoinduction.

The conditioning of culture medium by the production of growth-regulatory substances is a well-established phenomenon with eukaryotic cells. It has recently been shown that many prokaryotes are also capable of modulating growth, and in some cases sensing cell density, by production of extracellular signaling molecules, thereby allowing single celled prokaryotes to function in some respects as multicellular organisms. As Escherichia coli shifts from exponential growth to stationary growth, many changes occur, including cell division leading to formation of short minicells and expression of numerous genes not expressed in exponential phase.

Effect of metal-ligand mutations on phosphoryl transfer reactions catalyzed by Escherichia coli glutamine synthetase.

Glutamine synthetase (GS) converts glutamate to glutamine in the presence of ATP and ammonia and requires two divalent metal ions, designated n1 and n2, for catalysis. The first intermediate, gamma-glutamyl phosphate, is formed during catalysis by the transfer of the gamma-phosphate of ATP to the gamma-carboxylate of glutamate. Efficient phosphoryl transfer between these two negatively charged moieties is thought to be mediated by the n2 metal.

Transcriptional regulation of bioluminesence genes from Vibrio fischeri.

The phenomenon of cell-density-dependent control of gene expression, called autoinduction, has long been a subject of interest and investigation in bioluminescent marine bacteria. It is now becoming clear that many other bacteria, including animal and plant pathogens, use an autoinduction mechanism to regulate a variety of functions. Cell-density-dependent gene expression provides an excellent example of multicellular behaviour in the prokaryotic kingdom where a single cell is able to communicate and sense when a minimal population unit, a 'quorum' of bacteria, is achieved in order for certain behaviour of the population to be performed efficiently.

Regeneration of catalytic activity of glutamine synthetase mutants by chemical activation: exploration of the role of arginines 339 and 359 in activity.

In order to understand the nature of ATP and L-glutamate binding to glutamine synthetase, and the involvement of Arg 339 and Arg 359 in catalysis, these amino acids were changed to cysteine via site-directed mutagenesis. Individual mutations (Arg-->Cys) at positions 339 and 359 led to a sharp drop in catalytic activity. Additionally, the Km values for the substrates ATP and glutamate were elevated substantially above the values for wild-type (WT) enzyme.