title: A balancing act times two: sensing and regulating cell envelope homeostasis in Bacillus subtilis.
abstract: Bacterial cell wall homeostasis is an intricately coordinated process that ensures that envelope integrity is maintained during cell growth and division, but can also adequately respond to growth-limiting conditions such as phosphate starvation. In Bacillus subtilis, biosynthesis of the two major cell wall components, peptidoglycan and anionic polymers, is controlled by a pair of paralogous two-component systems, WalRK and PhoPR respectively. Favorable growth conditions allow for a fast rate of cell wall biosynthesis (WalRK-ON) and the incorporation of the phosphate-containing anionic polymer teichoic acids (PhoPR-OFF). In contrast, growth-restricted cells under phosphate-limiting conditions reduce the incorporation of peptidoglycan building blocks (WalRK-OFF) and switch from the phosphate-containing teichoic acids to the phosphate-free anionic polymer teichuronic acid (PhoPR-ON). Botella et al. (2014) deepen our knowledge on the PhoPR system by identifying one signal that is perceived by its histidine kinase PhoR. In fast-growing cells, intracellular intermediates of teichoic acid biosynthesis are sensed by the cytoplasmic Per-Arnt-Sim domain as an indicator of favorable conditions, thereby inhibiting the autokinase activity of PhoR and keeping the system inactive. Depletion of teichoic acid building blocks under phosphate-limiting conditions relieves this inhibition, activates PhoPR-dependent signal transduction and hence the switch to teichuronic acid biosynthesis.
authors.affiliation: LOEWE Center for Synthetic Microbiology, Philipps-University Marburg, 35043, Marburg, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Fritz
authors.forename: Thorsten
authors.initials: T
authors.lastname: Mascher
mesh_terms: D001412:Bacillus subtilis / Q000254:growth & development*; D001426:Bacterial Proteins / Q000235:genetics*; D010710:Phosphates / Q000378:metabolism*; D013682:Teichoic Acids / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D010710:Phosphates; D013682:Teichoic Acids