The influence of ionic strength, nutrients and pH on bacterial adhesion to metals

The force of bacterial adhesion to the metal surface is influenced by the nutrients and the ionic strength of the solution.

Journal of Colloid and Interface Science
Volume 321, Issue 2, Pages 256-264 (15 May 2008)
Xiaoxia Sheng, Yen Peng Ting, Simo Olavi Pehkonen

Abstract: Bacteria–metal interactions in aqueous solutions are important in biofilm formation, biofouling and biocorrosion problems in the natural environment and engineered systems. In this study, the adhesion forces of two anaerobes (Desulfovibrio desulfuricans and Desulfovibrio singaporenus) and an aerobe (Pseudomonas sp.) to stainless steel 316 in various aqueous systems were quantified using atomic force microscopy (AFM) with a cell probe. Results show that the nutrient and ionic strength of the solutions influence the bacteria–metal interactions. The bacteria–metal adhesion force was reduced in the presence of the nutrients in the solution, because a trace organic film was formed and thus decreased the metal surface wettability. Stronger ionic strength in the solution results in a larger bacteria–metal adhesion force, which is due to the stronger electrostatic attraction force between the positively charged metal surface and negatively charged bacterial surface. Solution pH also influences the interaction between the bacterial cells and the metal surface; the bacteria–metal adhesion force reached its highest value when the pH of the solution was near the isoelectric point of the bacteria, i.e. at the zero point charge. The adhesion forces at pH 9 were higher than at pH 7 due to the increase in the attraction between Fe ions and negative carboxylate groups.
Article Outline

1. Introduction
2. Experimental procedures
2.1. Cell growth conditions
2.2. Cell immobilization
2.3. Solutions
2.4. Zeta potential (ζ) measurements
2.5. Contact angle measurements
2.6. Confocal laser scanning microscopy (CLSM) analysis
2.7. AFM operation
2.8. X-ray photoelectron spectroscopy (XPS) analysis
3.Results and discussion
3.1. Influence of nutrient and solution ionic strength on the cell–metal interaction
3.2. Influence of solution pH on the cell–metal interactions
4. Conclusions
Acknowledgements
References