Department of Desalination and Water Treatment, Zuckerberg Institute for Water Research, Ben-Gurion University of the Negev, Sede Boqer Campus 84990, Israel.
Biofouling. 2011 Aug;27(7):787-98. doi: 10.1080/08927014.2011.603145.
Among various functions, extracellular polymeric substances (EPS) provide microbial biofilms with mechanical stability and affect initial cell attachment, the first stage in the biofilm formation process. The role of alginate, an abundant polysaccharide in Pseudomonas aeruginosa biofilms, in the viscoelastic properties and adhesion kinetics of EPS was analyzed using a quartz crystal microbalance with dissipation (QCM-D) monitoring technology. EPS was extracted from two P. aeruginosa biofilms, a wild type strain, PAO1, and a mucoid strain, PAOmucA22 that over-expresses alginate production. The higher alginate content in the EPS originating from the mucoid biofilms was clearly shown to increase both the rate and the extent of attachment of the EPS, as well as the layer's thickness. Also, the presence of calcium and elevated ionic strength increased the thickness of the EPS layer. Dynamic light scattering (DLS) showed that the presence of calcium and elevated ionic strength induced intermolecular attractive interactions in the mucoid EPS molecules. For the wild type EPS, in the presence of calcium, an elevated shift in the distribution of the diffusion coefficients was observed with DLS due to a more compacted conformation of the EPS molecules. Moreover, the alginate over-expression effect on EPS adherence was compared to the effect of alginate over-expression on P. aeruginosa cell attachment. In a parallel plate flow cell, under similar hydraulic and aquatic conditions as those applied for the EPS adsorption tests in the QCM-D flow cell, reduced adherence of the mucoid strain was clearly observed compared to the wild type isogenic bacteria. The results suggest that alginate contributes to steric hindrance and shielding of cell surface features and adhesins that are known to promote cell attachment.
在各种功能中，细胞外聚合物质（EPS）为微生物生物膜提供机械稳定性，并影响初始细胞附着，这是生物膜形成过程的第一阶段。使用石英晶体微天平耗散（QCM-D）监测技术分析了在 Pseudomonas aeruginosa 生物膜中丰富的多糖——藻酸盐在 EPS 的粘弹性和附着动力学中的作用。从两种 P. aeruginosa 生物膜中提取了 EPS，一种是野生型菌株 PAO1，另一种是过度表达藻酸盐产生的粘液型菌株 PAOmucA22。粘液型生物膜 EPS 中更高的藻酸盐含量明显增加了 EPS 的附着速率和程度，以及层的厚度。此外，钙的存在和升高的离子强度增加了 EPS 层的厚度。动态光散射（DLS）表明，钙的存在和升高的离子强度诱导了粘液型 EPS 分子之间的分子间吸引力相互作用。对于野生型 EPS，在钙存在的情况下，DLS 观察到扩散系数分布的升高偏移，这是由于 EPS 分子的更紧凑构象。此外，将藻酸盐过表达对 EPS 附着的影响与藻酸盐过表达对 P. aeruginosa 细胞附着的影响进行了比较。在平行板流动池中，在与 QCM-D 流动池中的 EPS 吸附测试中应用的水力和水生条件相似的情况下，与野生型同源细菌相比，粘液型菌株的附着明显减少。结果表明，藻酸盐有助于阻止和屏蔽细胞表面特征和粘附素，这些特征和粘附素已知可促进细胞附着。
