Novel roles for stringent response in bacteria physiology
Farshid Jalalvand, from University of Copenhagen in Denmark, will give a talk about "CRISPRi-mediated screen of essential processes in E. coli reveals novel roles for (p)ppGpp in outer membrane biogenesis and ADP metabolism”.
Brief description of research Bacteria, as all other life forms, encounter a variety of stresses in nature that must be competently sensed and countered in order to ensure survival. One of the central stress responding pathways in Escherichia coli is the stringent response, which via the production of the nucleotide alarmone (p)ppGpp halts macromolecular biosynthesis, induces reduced growth rates and re-directs cellular resources to survival pathways.
Whereas the role of (p)ppGpp has been extensively studied in response to external stresses, such as amino acid starvation, much less is known about its function in coordination growth during intracellular process imbalances in E. coli. In order to screen for novel roles for (p)ppGpp, we employed CRISPRi to perturb 14 essential cellular processes (cell division, cytoskeleton biogenesis, DNA replication, essential GTPase activity, lipoprotein incorporation in the outer membrane, lipopolysaccharides biosynthesis and outer membrane biogenesis, nucleotide metabolism, outer membrane protein assembly, peptidoglycan synthesis, phospholipid biosynthesis, extracellular secretion, transcription, translation and tRNA-charging).
Our data revealed that (p)ppGpp is produced and required for a pertinent stress response during disturbances in outer membrane biogenesis and ADP metabolism. Whereas wild type E. coli MG1655 would enter a semidormant state during transcriptional suppression of the related genes, the isogenic (p)ppGpp0 strain were found to grow uncontrollably to the point of lysis when adenosine ribonucleotide metabolism and outer membrane biogenesis were perturbed. In summary, our investigation implicates the stringent response in the regulation of cell growth during intracellular imbalances in E. coli, indicating hitherto overlooked roles in bacterial physiology.