We show that growth conditions organize the mechanics of Pseudomonas fluorescens biofilms into two separable contributions: a structural elastic backbone and a rate-sensitive attenuation of elastic load bearing under fixed-amplitude oscillatory forcing. Biofilms grown under both static and shaken conditions display weakly dispersive viscoelasticity at low frequency, consistent with a soft-glassy-like elastic background. At higher frequencies, mature biofilms grown under static conditions undergo a pronounced suppression of the storage modulus and cross into a dissipation-dominated regime, whereas shaken biofilms preserve a predominantly solid-like response. Particle-based simulations with permanent crosslinks recover the observed association between elastic stiffness and crossover timescale, establishing permanent connectivity as a sufficient structural route to this dynamical scaling within the simulated model. Their persistent high-frequency elastic response isolates the attenuation observed experimentally as a distinct kinetic contribution. We represent this contribution with a minimal kinetic model in which the effective load-bearing response progressively decreases above a characteristic forcing scale. The combined results establish a structural-kinetic decomposition in which connectivity sets the stiffness and characteristic timescale of the elastic backbone, while kinetics regulates its engagement under rapid forcing. This framework links growth-conditioned architecture to rate-sensitive elasticity in biofilms and other restructuring disordered materials.

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• Organismal, population, evolutionary & ecological systems
• Phase transitions in biological systems