Table 3.

Composition and function of the Rcs phosphorelay system.

Rcs characteristic dimension	Core components/signals	Significance	Reference
Composition	RcsF, RcsC, RcsD, RcsB; multistep phosphorelay	Enables signal integration and stepwise transduction	(Zhang and Shi, 2005; Li et al., 2024)
Activation	Responds to periplasmic/cell width changes and antibiotic stress	Specifically monitors envelope integrity	(Zietek et al., 2025)
Signal transduction	Periplasmic thinning brings RcsF to inner membrane, activating cascade	Converts physical damage into chemical signal	(Zietek et al., 2025)
Effector response	RcsB activates capsule synthesis and stress genes	Remodels cell surface to adapt to environmental stress	(Li et al., 2024)
Resistance mechanism	Capsule thickening may reduce drug penetration; negative charge may contribute to aminoglycoside exclusion; may regulate FtsZ	May contribute to heteroresistance	(Campos et al., 2004; Wall et al., 2018)
Specificity	Senses cell width/periplasmic thickness; distinct from CpxRA	Specific defense, complementary to CpxRA	(Zietek et al., 2025)