剪切流对细菌从几丁质颗粒脱附的影响

Effects of Shear Flow on Bacterial Desorption from Chitin Particles

水体环境中微生物在有机物颗粒上定殖组成群落,调控着物质循环的进程.而颗粒上微生物的运动、行为及空间分布会受到流动的影响.细菌在颗粒表面定殖的分子机制已有深入研究,流动对细菌从颗粒脱附的影响却知之甚少.设计了微流体实验定量研究剪切流对细菌从几丁质颗粒脱附的影响及细菌行为的响应,实验结果表明,剪切力分别为1.37×10^(-2)Pa、4.11×10^(-2)Pa、13.69×10^(-2)Pa时,细菌的脱附速率较静水工况分别增加了4.41×10^(-2)h^(-1)、5.89×10^(-2)h^(-1)、9.21×10^(-2)h^(-1);即细菌的脱附速率随剪切力增加而增加,但脱附速率增加比例不及剪切力的增加比例.进一步研究发现,存在剪切流时,细菌会趋于平行于流向,吸附姿态从端状吸附过渡为吸附能力更强的纵向吸附,这两种变化规律会随着剪切力的增加而增强,这种适应性变化有助于细菌抵御剪切流的影响.

The nutrient turnover process in water environment is regulated by microbial community that colonizes organic particles.Meanwhile,flows affect the movement,behavior and spatial distribution of microorganisms on particles.The molecular mechanism of bacterial colonization on particle surface has been extensively studied,whereas little is known about the effects of flow on bacterial desorption from particles.A microfluidic experiment was designed to quantitatively investigate the effects of shear flow on bacterial desorption from chitin particles and the response of bacterial behavior.The experimental results showed that when the shear forces are 1.37×10^(-2)Pa,4.11×10^(-2)Pa,and 13.69×10^(-2)Pa,the bacterial desorption rates are respectively 4.41×10^(-2)h^(-1),5.89×10^(-2)h^(-1),and 9.21×10^(-2)h^(-1)greater than the desorption rate in static water.In other words,even though the desorption rate increase with the increase of shear force,the increase of the former is much significant than the latter.Furthermore,it was found that due to shear flow bacteria tend to align with the flow direction,and the adsorption posture change from polar adhesion to longitudinal adhesion,causing stronger adsorption capacity.Both the two changes get more significant with increase of shear force,and such adaptational changes are helpful for bacteria to resist the influence of shear flow.