[Eco-physiological functions of soil microbial biofilms: A review]

Soil microbial biofilms (SMBs) are a biological community of soil bacteria and their accumulative extracellular polymeric substances (EPS), which are the initial status and the most important components of biological soil crusts. SMBs, as the most common mode of soil bacterium survival, not only greatly contribute to the survival of free-living cells, but also stick to soil particles and roots, performing a variety of important ecological functions. Based on the structure and composition analysis of SMBs, we gave a summary of eco-physiological functions of SMBs involving soil quality and plant health. SMBs have higher metabolic activity than free-living cells. It promotes EPS secretion and organic turnover, which is important for soil fertility, pollutant decomposition, and aggregate formation. SMBs help improve plant nutrient utilization and stress resistance through the synergy of microorganisms, promotion of plant growth, promoting substance secretion and immobilization of EPS. In the future, it will be critical to uncover the micro-mechanisms underlying SMBs' eco-physiological functions and to screen functional soil bacterium strains.