Li Xiaobao, Chopp David L, Russin William A, Brannon Paul T, Parsek Matthew R, Packman Aaron I
Department of Civil and Environmental Engineering, Northwestern University, Evanston, Illinois, USA.
Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, Illinois, USA.
Appl Environ Microbiol. 2016 May 2;82(10):2886-92. doi: 10.1128/AEM.03954-15. Print 2016 May 15.
Microbial biofilms and mineral precipitation commonly co-occur in engineered water systems, such as cooling towers and water purification systems, and both decrease process performance. Microbial biofilms are extremely challenging to control and eradicate. We previously showed that in situ biomineralization and the precipitation and deposition of abiotic particles occur simultaneously in biofilms under oversaturated conditions. Both processes could potentially alter the essential properties of biofilms, including susceptibility to biocides. However, the specific interactions between mineral formation and biofilm processes remain poorly understood. Here we show that the susceptibility of biofilms to chlorination depends specifically on internal transport processes mediated by biomineralization and the accumulation of abiotic mineral deposits. Using injections of the fluorescent tracer Cy5, we show that Pseudomonas aeruginosa biofilms are more permeable to solutes after in situ calcite biomineralization and are less permeable after the deposition of abiotically precipitated calcite particles. We further show that biofilms are more susceptible to chlorine killing after biomineralization and less susceptible after particle deposition. Based on these observations, we found a strong correlation between enhanced solute transport and chlorine killing in biofilms, indicating that biomineralization and particle deposition regulate biofilm susceptibility by altering biocide penetration into the biofilm. The distinct effects of in situ biomineralization and particle deposition on biocide killing highlight the importance of understanding the mechanisms and patterns of biomineralization and scale formation to achieve successful biofilm control.
微生物生物膜和矿物质沉淀在工程水系统中普遍共存，如冷却塔和水净化系统，二者都会降低工艺性能。微生物生物膜极难控制和根除。我们之前表明，在过饱和条件下，生物膜中会同时发生原位生物矿化以及非生物颗粒的沉淀和沉积。这两个过程都可能改变生物膜的基本特性，包括对杀菌剂的敏感性。然而，矿物形成与生物膜过程之间的具体相互作用仍知之甚少。在此我们表明，生物膜对氯化作用的敏感性具体取决于由生物矿化介导的内部传输过程以及非生物矿物沉积物的积累。通过注射荧光示踪剂Cy5，我们发现，原位方解石生物矿化后，铜绿假单胞菌生物膜对溶质的渗透性更高，而非生物沉淀的方解石颗粒沉积后，其渗透性则更低。我们进一步表明，生物矿化后生物膜对氯杀灭作用更敏感，颗粒沉积后则较不敏感。基于这些观察结果，我们发现生物膜中溶质传输增强与氯杀灭作用之间存在很强的相关性，这表明生物矿化和颗粒沉积通过改变杀菌剂渗入生物膜的情况来调节生物膜的敏感性。原位生物矿化和颗粒沉积对杀菌剂杀灭作用的不同影响凸显了了解生物矿化和水垢形成的机制及模式对于成功控制生物膜的重要性。
