Effect of Substratum Surface Chemistry and Surface Energy on Attachment of Marine Bacteria and Algal Spores

Abstract

Two series of self-assembled monolayers (SAMs) of -substituted alkanethiolates on gold were used to systematically examine the effects of varying substratum surface chemistry and energy on the attachment of two model organisms of interest to the study of marine biofouling, the bacterium Cobetia marina (formerly Halomonas marina) and zoospores of the alga Ulva linza (formerly Enteromorpha linza). SAMs were formed on gold-coated glass slides from solutions containing mixtures of methyl-and carboxylic acid-terminated alkanethiols and mixtures of methyl-and hydroxyl-terminated alkanethiols. C. marina attached in increasing numbers to SAMs with decreasing advancing water contact angles ( AW ), in accordance with equation-of-state models of colloidal attachment. Previous studies of Ulva zoospore attachment to a series of mixed methyl-and hydroxyl-terminated SAMs showed a similar correlation between substratum AW and zoospore attachment. When the hydrophilic component of the SAMs was changed to carboxylate, however, the profile of attachment of Ulva was significantly different, suggesting that a more complex model of interfacial energetics is required.Upon submersion in a nonsterile aqueous liquid, most surfaces become rapidly colonized by collections of bacteria and other microorganisms. These attached cells, along with extracellular material they produce and other organic compounds adsorbed to the surface, comprise a structure referred to as a biofilm (17). Biofilms are ubiquitous in natural aqueous milieus and are increasingly considered to represent a separate developmental form of microorganisms (29). Similarly, a number of macroorganisms, such as algae, exploit a unicellular form for attachment and colonization of surfaces. Surface coverage by both macro-and microorganisms, therefore, depends initially on the ability of single cells to adsorb and adhere to the attachment substratum.The tendency (driving force) for a microorganism to attach to a given surface is given by the free energy of adhesion (⌬G adh ), which can be expressed by the following equation as a thermodynamic energy balance between the interfacial energies between the substratum, the organism, and the surrounding liquid (1): ⌬G adh ϭ ␥ BS Ϫ ␥ BL Ϫ ␥ SL , where ␥ BS is the interfacial tension between the organism (e.g., a bacterium) and substratum, ␥ BL is the interfacial tension between the organism and the liquid, and ␥ SL is the interfacial tension between the substratum and the liquid.Experimental determination of the interfacial energy values for the above equation is controversial and has led to three different, yet complementary, models (8). All rely on estimation of interfacial energies by contact angles as indicated by Young's equation (2), which states that ␥ SV (the vapor interfacial tensions [surface tensions] of the substratum) is related to the contact angle () formed by a drop of liquid on the substratum such that ␥ SV ϭ ␥ SL ϩ ␥ LV cos, where ␥ SL is the interfacial tension between the surface and the liquid and ␥ LV is the interfac...

Surface Sensing and Settlement Strategies of Marine Biofouling Organisms

“…Application of SAM in biofouling research was pioneered by the Lopez group [25,64]. Extensive studies followed, focusing on various surface properties including wettability, hydration, and lubricity [31,33,64,67,77,78]. Figure 6a shows a compiled viewgraph of Ulva linza zoospore settlement, Navicula perminuta settlement, and protein resistance on different aliphatic SAMs [64], methyl terminated oligosaccharide SAMs [48,65], and oligoethyleneglycol based SAMs with aliphatic termination [31].…”

Microfluidic Assay to Quantify the Adhesion of Marine Bacteria

“…One major advantage is that the mechanical properties are determined by the substrate while physicochemical properties, such as wetting and hydration are determined by the thin organic film. The accumulation of C. marina on chemically differently terminated self-assembled monolayers (SAMs) revealed that surface properties change the amount of accumulated biomass [14,29]. In this article we describe the effect of undecanethiol SAMs with -CH 3 , -NH 2 , -OC 7 F 10 CF 3 termination and polyethylene glycol (PEG) terminated SAMs on the adhesion strength of the marine bacteria C. marina.…”

“…To demonstrate the applicability of the microfluidic assay, we used self-assembled monolayers as welldefined model surfaces. Self-assembled monolayers [25,26] are highly useful tools to reproducibly prepare coatings and frequently applied to study response of marine biofouling organisms [14,16,[27][28][29][30][31][32]. One major advantage is that the mechanical properties are determined by the substrate while physicochemical properties, such as wetting and hydration are determined by the thin organic film.…”

Progress of marine biofouling and antifouling technologies

“…Ulva spores were demonstrated to have a reduced tendency to settle on negatively charged surfaces of polytetrafluoroethylene (PTFE) [64]. Many other phenomena observed during microorganism settlement on self-assembled monolayers [121,144] can be partly explained by electrostatic interactions [145,146]. Discharge treatment can be used to create carboxylic acid groups on polymer surfaces [147], which can also be discussed in terms of the repulsive electrostatic interactions [148].…”

“…Study has shown that fouling diatoms [37] adhere more strongly to a hydrophobic polydimethylsiloxane (PDMSE) surface than to glass. For other fouling organisms such as bacteria and Ulva spores, if the surface contact angle is greater than the adhesion is stronger [121][122][123][124]. However, the strength of attachment of Ulva spores is greater to hydrophilic than hydrophobic surfaces [66,125].…”