The significance of biofilms to human, animal, plant and ecosystem health

Biofilms are matrix‐enclosed communities that represent the most dominant and active mode of microbial life on Earth. Because biofilms are inherently more productive than any equivalent planktonic community, they are of great relevance to all environments they inhabit. However, their existence and importance are still poorly known by the general public, conservation practitioners and environmental policymakers. Most micro‐organisms of multicellular organisms (including humans, animals and plants) occur in the form of true biofilms or biofilm‐like structures that play vital roles in their development, physiology and immunity. Conversely, some biofilms can have a negative effect on host health. Biofilms growing on non‐biological surfaces are essential components of many terrestrial and marine ecosystems: they form the basis of food webs and ensure nutrient cycling and bioremediation in natural systems. However, environmental biofilms can promote the persistence of human pathogens, produce harmful toxins, foul and corrode surfaces in natural and man‐made settings; all of which can have significant health and economic implications. There is a knowledge gap about the roles of biofilms in the epidemiology of wildlife emerging infectious diseases, yet these pose a major threat to public health, biodiversity and sustainability. The drivers of global environmental change all affect biofilm structure and functions. The consequences for host and ecosystem health are, however, poorly understood. While the concept of a healthy microbiome (as opposed to dysbiosis) is emerging in medicine and conservation biology, the concept of a healthy biofilm remains to be defined in environmental sciences. Here, we use an integrative approach to (a) review current knowledge on the roles of biofilms growing on biological and non‐biological interfaces for the health of multicellular organisms and ecosystems, and (b) provide future research directions to address identified knowledge gaps. Giving the biofilm life‐form its full importance will help understand the effects of global environmental change on these communities and, in turn, on human, animal, plant and ecosystem health.