Hong Yongsuk, Brown Derick G
Department of Civil and Environmental Engineering, Lehigh University, 13 East Packer Avenue, Bethlehem, Pennsylvania 18015, USA.
Appl Environ Microbiol. 2009 Apr;75(8):2346-53. doi: 10.1128/AEM.02671-08. Epub 2009 Feb 13.
Bacterial adhesion to natural and man-made surfaces can be beneficial or detrimental, depending on the system at hand. Of vital importance is how the process of adhesion affects the bacterial metabolic activity. If activity is enhanced, this may help the cells colonize the surface, whereas if activity is reduced, it may inhibit colonization. Here, we report a study demonstrating that adhesion of both Escherichia coli and Bacillus brevis onto a glass surface resulted in enhanced metabolic activity, assessed through ATP measurements. Specifically, ATP levels were found to increase two to five times upon adhesion compared to ATP levels in corresponding planktonic cells. To explain this effect on ATP levels, we propose the hypothesis that bacteria can take advantage of a link between cellular bioenergetics (proton motive force and ATP formation) and the physiochemical charge regulation effect, which occurs as a surface containing ionizable functional groups (e.g., the bacterial cell surface) approaches another surface. As the bacterium approaches the surface, the charge regulation effect causes the charge and pH at the cell surface to vary as a function of separation distance. With negatively charged surfaces, this results in a decrease in pH at the cell surface, which enhances the proton motive force and ATP concentration. Calculations demonstrated that a change in pH across the cell membrane of only 0.2 to 0.5 units is sufficient to achieve the observed ATP increases. Similarly, the hypothesis indicates that positively charged surfaces will decrease metabolic activity, and results from studies of positively charged surfaces support this finding.
细菌对天然和人造表面的黏附可能有益也可能有害，这取决于具体的系统。至关重要的是黏附过程如何影响细菌的代谢活性。如果活性增强，这可能有助于细胞在表面定殖，而如果活性降低，则可能抑制定殖。在此，我们报告一项研究，该研究表明通过ATP测量评估，大肠杆菌和短短芽孢杆菌在玻璃表面的黏附均导致代谢活性增强。具体而言，与相应浮游细胞中的ATP水平相比，黏附后ATP水平增加了两到五倍。为了解释对ATP水平的这种影响，我们提出一个假设，即细菌可以利用细胞生物能学（质子动力势和ATP形成）与物理化学电荷调节效应之间的联系，这种效应在含有可电离官能团的表面（例如细菌细胞表面）接近另一个表面时会发生。当细菌接近表面时，电荷调节效应会导致细胞表面的电荷和pH值随分离距离而变化。对于带负电荷的表面，这会导致细胞表面pH值降低，从而增强质子动力势和ATP浓度。计算表明，细胞膜两侧pH值仅变化0.2至0.5个单位就足以实现观察到的ATP增加。同样，该假设表明带正电荷的表面会降低代谢活性，对带正电荷表面的研究结果支持了这一发现。
