Plant-derived bioactive compounds at sub-lethal concentrations: towards smart biocide-free antibiofilm strategies

Biofilm resistance to biocides is becoming a global issue with an impact on many fields, including health care, agriculture, the environment, society and industry. Plants offer a virtually inexhaustible and sustainable resource of very interesting classes of biologically active, low-molecular-weight compounds (parvome). In the past, the plant parvomes were screened mainly for their lethal effects, disregarding concentrations and ecologically relevant functions of these molecules in the natural context. Testing sub-lethal concentrations of plant-derived compounds mimicking environmental levels may be critical to reveal mechanisms subtler than the killing activity, e.g. those influencing the multicellular behavior, offering an elegant way to develop novel biocide-free antibiofilm strategies. In a cross-disciplinary fashion, we illustrated recent successes of sub-lethal concentrations of plant-derived compounds, their ecological insight, pro et contra, future directions and impacts, envisioning implications for policy making and resource management.