Characterization of biofilm formation in natural water subjected to low-frequency electromagnetic fields

Electromagnetic field (EMF) treatment has proven to be effective against mineral scaling in water systems. Therefore, it should be assessed for the treatment of other deposits such as biofilms. In this study, a commercial device producing low-frequency EMF (1–10 kHz) was applied to a reactor fed with natural water for 45 days. The treatment promoted the concentration of microorganisms in suspension and limited the amount of sessile microorganisms in the biofilm, as determined by the measurement of total DNA, qPCR and microscopy. The structure of the bacterial community was assessed by t-RFLP and pyrosequencing analysis. The results showed that EMF treatment affected both planktonic and sessile community composition. EMFs were responsible for a shift in classes of Proteobacteria during development of the biofilm. It may be speculated that the EMF treatment affected particle solubility and/or microorganism hydration. This study indicated that EMFs modulated biofilm formation in natural water.电磁场（Electromagnetic Field，EMF）处理已被证实可有效抑制水系统中的矿物结垢，因此有必要评估其用于处理生物膜等其他沉积物的可行性。本研究采用一款可产生1~10 kHz低频电磁场的商用设备，对以天然水为进水的反应器进行了为期45天的处理。经总DNA定量、实时荧光定量PCR（quantitative real-time PCR，qPCR）及显微镜观测证实，该处理可提升悬浮态微生物浓度，同时减少生物膜内固着态微生物的数量。研究通过末端限制性片段长度多态性（terminal restriction fragment length polymorphism，t-RFLP）与焦磷酸测序分析，对细菌群落结构进行了表征。结果表明，电磁场处理同时改变了浮游态与固着态细菌群落的组成结构；在生物膜形成过程中，电磁场会引发变形菌门（Proteobacteria）各纲的群落组成偏移。推测电磁场处理可能通过改变颗粒物溶解度或微生物水合状态发挥作用。本研究证实，电磁场可调控天然水环境中的生物膜形成过程。