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

Abstract

The conditioning of culture medium by the production of growth-regulatory substances is a wellestablished 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. An understanding of the coordination between the morphological changes associated with cell division and the physiological and metabolic changes is of fundamental importance to understanding regulation of the prokaryotic cell cycle. The ftsQA genes, which encode functions required for cell division in E. coli, are regulated by promoters Pi and P2, located upstream of the ftsQ gene. The P1 promoter is rpoSstimulated and the second, P2, is regulated by a member of the LuxR subfamily of transcriptional activators, SdiA, exhibiting features characteristic of an autoinduction (quorum sensing) mechanism. The activity of SdiA is potentiated by N-acylhomoserine lactones, which are the autoinducers of luciferase synthesis in luminous marine bacteria as well as of pathogenesis functions in several pathogenic bacteria. A compound(s) produced by E. coli itself during growth in Luria Broth stimulates transcription from P2 in an SdiA-dependent process. Another substance(s) enhances transcription of rpoS and (perhaps indirectly) offtsQA via promoter P1. It appears that this bimodal control mechanism may comprise a fail-safe system, such that transcription of the ftsQA genes may be properly regulated under a variety of different environmental and physiological conditions.

Analysis of the effect of ppGpp on the ftsQAZ operon in Escherichia coli

“…The 'stationary phase' sigma factor RpoS stimulates transcription from pQ1 (Sitnikov et al, 1996;M. Ballesteros, S. Kusano, A. Ishihama and M. Vicente, personal communication) and RpoS synthesis is stimulated by high ppGpp levels (Gentry et al, 1993).…”

Mutants of Mycobacterium smegmatis impaired in stationary-phase survival The GenBank accession numbers for the sequences determined in this work are: AJ277088 (mutant 272A), AJ277089 (mutant 272E), AJ27790 (mutant 317C), AJ277152 (mutant 492A) and AJ276883 (mutant 3910D).

“…The apparent role of a PBP in stationaryphase survival of M. smegmatis is consistent with the dynamic nature of stationary-phase cultures and the appearance of new variants, which presumably requires growth and cell division (Smeulders et al, 1999). Several genes, including bolA and ftsQAZ (Ballesteros et al, 1998, Bohannon et al, 1991Sitnikov et al, 1996), that are involved in the determination of cell shape and structure in E. coli are regulated by the stationary-phase sigma factor RpoS. It has recently been shown that E. coli strains lacking both PBP3 and RpoS have a stationary-phase survival defect similar to the defect in surA rpoS double mutants.…”

Specific growth rate and not cell density controls the general stress response in Escherichia coli

“…Several studies showed that supernatant fluid from stationaryphase batch cultures, which should contain quorum-sensing signal molecules, had little or no effect on rpoS : : lacZ transcriptional and translational fusions (Garcia-Lara et al, 1996;Sitnikov et al, 1996;Hengge-Aronis, 2002). Furthermore, intracellular RpoS concentrations, as well as rpoS mRNA levels, did not increase in parallel with cell density in fed-batch culture (Teich et al, 1999;Yoon et al, 2003).…”