Tsagkari Erifyli, Sloan William
School of Engineering, University of Glasgow, Glasgow G12 8QQ, UK.
Microorganisms. 2023 Oct 31;11(11):2680. doi: 10.3390/microorganisms11112680.
Water companies make efforts to reduce the risk of microbial contamination in drinking water. A widely used strategy is to introduce chlorine into the drinking water distribution system (DWDS). A subtle potential risk is that non-lethal chlorine residuals may select for chlorine resistant species in the biofilms that reside in DWDS. Here, we quantify the thickness, density, and coverage of naturally occurring multi-species biofilms grown on slides in tap water with and without chlorine, using fluorescence microscopy. We then place the slides in an annular rotating reactor and expose them to fluid-wall shears, which are redolent of those on pipe walls in DWDS. We found that biofilms in chlorine experiment were thicker, denser and with higher coverage than in non-chlorine conditions under all flow regimes and during incubation. This suggests that the formation and development of biofilms was promoted by chlorine. Surprisingly, for both chlorinated and non-chlorinated conditions, biofilm thickness, density and coverage were all positively correlated with shear stress. More differences were detected in biofilms under the different flow regimes in non-chlorine than in chlorine experiments. This suggests a more robust biofilm under chlorine conditions. While this might imply less mobilization of biofilms in high shear events in pipe networks, it might also provide refuge from chlorine residuals for pathogens.
自来水公司努力降低饮用水中微生物污染的风险。一种广泛使用的策略是向饮用水分配系统（DWDS）中引入氯。一个潜在的细微风险是，非致死性的氯残留可能会在DWDS中的生物膜中选择出耐氯物种。在这里，我们使用荧光显微镜对在有氯和无氯的自来水中载玻片上生长的天然多物种生物膜的厚度、密度和覆盖率进行量化。然后，我们将载玻片放入环形旋转反应器中，使其暴露于类似于DWDS管壁上的流体-壁面剪切力之下。我们发现，在所有流动状态和培养过程中，氯实验中的生物膜比无氯条件下的生物膜更厚、更致密且覆盖率更高。这表明氯促进了生物膜的形成和发展。令人惊讶的是，对于氯化和非氯化条件，生物膜的厚度、密度和覆盖率均与剪切应力呈正相关。在无氯实验中不同流动状态下的生物膜中检测到的差异比在氯实验中更多。这表明在氯条件下生物膜更坚固。虽然这可能意味着在管网中的高剪切事件中生物膜的移动性较小，但它也可能为病原体提供躲避氯残留的庇护所。
