The importance of dissipation energy shift in analyzing bacteria–Surface interactions using a quartz crystal microbalance with dissipation monitoring

Bisphenol A (BPA) and atrazine are contaminants of emerging concern (CECs) that commonly accumulate near microbial biofilms in environmental and engineered systems. Because some bacteria can biodegrade CECs, understanding the proliferation of sessile microorganisms at solid–liquid interfaces is important. Quartz crystal microbalance with dissipation monitoring (QCM-D) enables real-time analysis of sessile bacterial growth, although frequency shifts can be complex due to viscoelastic effects, including overtone-dependent sign changes. Here, QCM-D responses were compared for two sessile cultures: a BPA-degrading bacterium and an atrazine-degrading consortium. BPA degradation was associated with negative frequency shifts across all overtones, whereas atrazine degradation produced both positive and negative frequency shifts depending on overtone. In contrast, dissipation shifts increased consistently for all overtones in both systems following exposure to the biodegradable CECs. These results demonstrate that dissipation shifts provide a robust indicator of sessile bacterial proliferation, even when frequency responses are ambiguous or exhibit sign reversals.