Multiple linear regression analysis of bacterial deposition to polyurethane coatings after conditioning film formation in the marine environment

Abstract

Many studies have shown relationships of substratum hydrophobicity, charge or roughness with bacterial adhesion, although bacterial adhesion is governed by interplay of different physico-chemical properties and multiple regression analysis would be more suitable to reveal mechanisms of bacterial adhesion. The formation of a conditioning film of organic compounds adsorbed from seawater affects the properties of substratum surfaces prior to bacterial adhesion, which is a complicating factor in studying the mechanism of bacterial adhesion. In this paper, the impact of conditioning films adsorbed from natural seawater to four polyurethane coatings with different hydrophobicity, elasticity and roughness was studied for three different marine bacterial strains in a multiple linear regression analysis. The water contact angle on hydrophobic coatings decreased on average by 8 degrees and increased on average by the same amount on hydrophilic coatings. These changes were accompanied by increased concentrations of oxygen and nitrogen on the surface as determined by X-ray photoelectron spectroscopy, indicative of adsorption of proteinaceous material. Furthermore, the mean surface roughness increased on average by 4 nm after conditioning film formation. Multiple linear regression analysis revealed that changes in deposition due to conditioning film formation of Marinobacter hydrocarbonoclasticus, Psychrobacter sp. SW5H and Halomonas pacifica in a stagnation-point flow chamber could be explained in a model comprising hydrophobicity and the prevalence of nitrogen-rich components on the surface for the most hydrophobic strain. For the two more hydrophilic strains, deposition was governed by a combination of surface roughness and hydrophobicity. Elasticity was not a factor in bacterial adhesion to conditioning films.

A conceptual model of organo-mineral interactions in soils: self-assembly of organic molecular fragments into zonal structures on mineral surfaces

“…With adsorption to a mineral, proteins may increase the number of reactive sites on the newly coated surface by exposing their abundant polar functional groups to the soil solution. This eVect is known as support preconditioning (Dufrene et al 1996), and is considered a routine step preceding the adhesion of microorganisms to mineral surfaces (Bos et al 1999;Bakker et al 2004). The surface charge densities of both protein and surface can vary with pH, and adsorption is typically greatest at the isoelectric point of the protein (Ramsden 1995).…”

Cross-Ocean Distribution of Rhodobacterales Bacteria as Primary Surface Colonizers in Temperate Coastal Marine Waters

“…These bacteria not only are abundant and ubiquitous in coastal waters (57) but also react to a low level of nutrient enrichment faster than other bacteria, such as the ␥-Proteobacteria and Bacteroidetes (1-3). The conditioning film could be a significant source of nutrients for the Roseobacter bacteria (5,21). The initial attachment may be an active and selective process, and surface sensing via two-component regulatory systems may be important (30).…”

Microbial Surface Colonization and Biofilm Development in Marine Environments

“…Proteins and glycoproteins are usually the major constituents of conditioning films (571,572), although lipids, polysaccharides, nucleic acids, aromatic amino acids, uronic acids, humic acids, and some other biomolecules may also be present (573). The conditioning film affects the surface nutritional conditions and physicochemical properties, usually causing a convergence of surfaces that initially vary strongly in hydrophobicity and roughness (6,7,572). The initial surface-colonizing microbial communities thus may be similar due to the masking effect of the conditioning film on the surface chemistry of different substrata (17, 574).…”