Biofilm-forming microorganisms in the rhizosphere to improve plant growth: Coping with abiotic stress and environmental pollution

Climate change and advancing anthropogenic environmental influences lead to more unpredictable conditions for crop growth. The use of mineral fertilizers to increase crop yield also often has environmental risks, making it necessary to consider other long-term alternatives to ensure sustainable agricultural production. In this context, plant growth-promoting microorganisms (PGPM) are increasingly becoming the focus of scientific studies due to their several benefits. Since PGPM not only improve the stress tolerance of the plants, but also promote their growth, they are particularly interesting with regard to increasing the crop productivity. Many PGPM are able to form biofilms that offer protection against abiotic stressors and have a high potential for use as bioremediators. Within the biofilm, different species are in exchange with each other, which can lead to synergistic effects, for example in the joint degradation of complex compounds. In order to select suitable microbial biostimulants, the interactions between the microorganisms and the plant need to be evaluated in detail, taking into account local conditions. Based on these data, appropriate selection and use of PGPM are made with more favorable results in crop yields even under adverse conditions. The main objective of this review is to give a state-of-the-art knowledge on biofilm-forming microorganisms in the rhizosphere to improve plant growth under different stress conditions, as well as the factors that affect the plant-microbe interaction. More than 300 scientific articles were considered in order to provide up-to-date information on the importance of biofilm-forming microorganisms in agricultural productivity as well as their contribution to ameliorate abiotic stress in plants caused by climate change and environmental pollution. This review uniquely emphasizes the multifaceted interactions within biofilms, providing new insights into the synergistic relationships among microbial communities and their collective impact on plant resilience and productivity. This review comprehensively examines the structure, composition, and morphology of biofilms in the rhizosphere. It highlights their significance in plant nutrition under drought and salinity stress conditions, as well as the role of PGPM in the degradation of emerging pollutants.