homeoviscous adaptation

Edge evidence

• temperature downshift causes membrane rigidification biolink:causes

  A temperature decrease causes the bacterial membrane to rigidify and thicken.

  • DOI:10.1128/spectrum.03925-23 Upon temperature decrease, the membrane rigidifies and increases in thickness Sidarta et al. describe rigidification and thickening as the immediate membrane response to temperature decrease.
• membrane rigidification positively regulates homeoviscous adaptation RO:0002213

  Membrane rigidification is sensed as the physical input that activates homeoviscous lipid remodeling.

  • DOI:10.1128/spectrum.03925-23 Upon temperature decrease, the membrane rigidifies and increases in thickness, resulting in activation of the kinase-dominant state of DesK Sidarta et al. support the physical membrane-state trigger through the B. subtilis DesK sensor model.
• homeoviscous adaptation positively regulates membrane lipid remodeling RO:0002213

  Homeoviscous adaptation increases lipid remodeling routes, including fatty-acyl desaturation, that counteract bilayer ordering.

  • DOI:10.1128/spectrum.03925-23 desaturates the fatty acyl chains, resulting in membrane fluidization and concomitant decrease of bilayer thickness Sidarta et al. support Des-mediated fatty-acyl desaturation as a concrete B. subtilis homeoviscous remodeling branch.
• FabI/FabB branchpoint enzymes regulates membrane lipid remodeling RO:0002211

  The E. coli FabI/FabB branchpoint valve allocates fatty-acid synthesis flux between saturated and unsaturated membrane-lipid routes.

  • DOI:10.1038/s41467-024-53677-5 A first element of this regulatory system is a temperature-sensitive metabolic valve that allocates flux between the saturated and unsaturated fatty acid synthesis pathways via the branchpoint enzymes FabI and FabB Hoogerland et al. support the E. coli FabI/FabB branchpoint valve as a regulator of flux between saturated and unsaturated fatty-acid synthesis.
• membrane lipid remodeling regulates membrane fluidity RO:0002211

  Temperature-dependent membrane lipid remodeling maintains membrane fluidity near a functional setpoint.

  • DOI:10.1038/s41467-024-53677-5 hard-wired parameters calibrate the system to generate membrane compositions that maintain constant fluidity Hoogerland et al. show that the E. coli fatty-acid synthesis system generates temperature-specific membrane compositions that maintain fluidity.
• membrane fluidity contributes to homeoviscous adaptation RO:0002326

  Restoration of optimal membrane fluidity is the physiological output of homeoviscous adaptation.

  • DOI:10.1038/s41467-024-53677-5 restores optimal membrane fluidity within a single generation Hoogerland et al. directly connect the homeoviscous fatty-acid control system to rapid fluidity restoration.