基于群体感应的生物膜技术在土壤污染修复中的应用与展望

生物膜修复技术凭借其高效性、安全性和经济性，已被广泛应用于土壤中难降解污染物的去除。其中，群体感应效应在生物膜修复过程中起着至关重要的作用。群体感应是微生物普遍存在的细胞间通讯形式，有助于生物膜内不同细菌种内/种间的信息交流，使微生物能够在“群体水平”上相互协作，能够调控生物膜胞外聚合物的生成以及对污染物的吸附固定与降解。本文在简要介绍生物膜和群体感应的功能和作用基础上，结合近年来群体感应调控生物膜形成以及对污染物的降解基础上，综述了群体感应在生物膜修复技术中的应用，最后对生物膜群体感应系统在污染土壤修复中的工程化设计进行了展望。

Application and Prospect of Biofilm Techniques Based on Quorum Sensing in Soil Pollution Remediation

Due to its high efficiency, safety and cost-effectiveness, biofilm remediation technology has been widely used in the removal of refractory pollutants in the environment. Biofilm technology refers to the adhesion, enrichment and reproduction of plankton microorganisms, eventually forming biofilm structure on the surface of the abiotic carrier, which leads to an increase in total biomass density and highly efficient metabolism of hydrophobic and toxic compounds. Compared with planktonic cells, a biofilm matrix can provide microorganisms with stronger resistance to high pressure of survival competition, harsh environmental conditions or harmful toxins. Changes in the local concentration of nutrients in the biofilm matrix and differences in the division of labor among microorganisms can induce differential gene expressions, leading to biofilm cells differing (phenotypically and metabolically) from the planktonic cells. It is beneficial for microorganisms to degrade pollutants through multiple metabolic pathways. Meanwhile, bacteria chemotaxis and flagellar movement can help the microorganism get access to pollutants, thereby improving their biodegradation efficiency. The formation and dispersal of biofilm are regulated by quorum sensing. The generation of extracellular polymeric substances is regulated by signal molecules by quorum sensing (QS), thereby changing the biofilm characteristics and enhancing the bioremediation of pollutants. Quorum sensing is a form of cell-cell communication among microorganisms. Through the diffusion of autoinducers among cellular matrix, bacteria can perceive cell density and species complexity and regulate their gene expressions when the concentration of signal molecules reaches a threshold level. So far, many different structural QS signals have been identified. Although many of them are specific among species, some QS signals can be produced and recognized by many species, thereby allowing inter-species communication. N-acyl homoserine lactones (AHLs) are often employed as QS signal molecules for many Gram-negative bacteria regulated by members of Luxl/R family genes, while Gram-positive bacteria use processed oligo-peptides to communicate. Biofilm formation and dispersal are genetic processes, therefore, they can be manipulated with synthetic biology tools like other genetic systems. Thus, biofilms and the biodegradation of pollutants may be controlled by manipulating signals. Successful application of a bioremediation process relies upon an understanding of interactions among microorganisms, contaminants and carrier materials. At present, more and more researches focus on pollution remediation using engineering biofilm technology, including in-situ and ex-situ bioremediation technology. During this process, quorum sensing or quorum quenching acts a crucial role. Quorum sensing plays a major role in various microbial physiological functions, such as biofilm formation and biofilm repair in polluted environments. Biofilms provide an optimal environment for cell-to-cell interactions, cell-to-cell exchange of genetic material and signals, and dispersal of metabolites. Biofilm quorum sensing technology exhibits an ideal application prospect in the remediation of contaminated soils. For the biofilm QS system, it is very important to clarify the generation rules of signal molecules among microorganisms, as well as the signal conduction path and its mechanism, which is conducive to the engineering design and application of functional bacteria. However, most of the well-studied QS systems are from Gram-negative bacteria. More research is needed to uncover and study the details of QS in a variety of microbial species, including Gram-positive bacteria and fungi. The role of QS in microbial populations, including QS crosstalk and signal specificity, is another important area of research that will impact strategies to regulate biofilm formation and pollutant elimination. Furthermore, QS signals regulation under defined conditions could contribute to the stability of the microbial community and the repair ability of functional microorganisms. Therefore, synthetic biologists should also focus on engineering mixed flora based on biofilm QS systems.