Department of Biochemistry, University of Wisconsin-Madison, Madison, WI 53706.Soft Matter (Impact Factor: 4.03). 05/2013; 9(18):4368-4380. DOI: 10.1039/C3SM27705D
The interaction of bacteria with surfaces has important implications in a range of areas, including bioenergy, biofouling, biofilm formation, and the infection of plants and animals. Many of the interactions of bacteria with surfaces produce changes in the expression of genes that influence cell morphology and behavior, including genes essential for motility and surface attachment. Despite the attention that these phenotypes have garnered, the bacterial systems used for sensing and responding to surfaces are still not well understood. An understanding of these mechanisms will guide the development of new classes of materials that inhibit and promote cell growth, and complement studies of the physiology of bacteria in contact with surfaces. Recent studies from a range of fields in science and engineering are poised to guide future investigations in this area. This review summarizes recent studies on bacteria-surface interactions, discusses mechanisms of surface sensing and consequences of cell attachment, provides an overview of surfaces that have been used in bacterial studies, and highlights unanswered questions in this field.
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- "This could be due to an influence of the surface modification on the expression of proteins involved in the electrochemical competence of this strain. Alternatively or additionally, the initial attachment of the bacteria might be hampered by hydrophilic surfaces as bacteria only tend to attach to hydrophilic surfaces if their surface energy is higher than in the suspending medium  . However, in order to verify this, an isolation of the found strain would be necessary, which was to date not successful , probably due to its very specific growth requirements. "
ABSTRACT: Several mixed microbial communities have been reported to show robust bioelectrocatalysis of oxygen reduction over time at applicable operation conditions. However, clarification of electron transfer mechanism(s) and identification of essential micro-organisms have not been realised. Therefore, the objective of this study was to shape oxygen reducing biocathodes with different microbial communities by means of surface modification using the electrochemical reduction of two different diazonium salts in order to discuss the relation of microbial composition and performance. The resulting oxygen reducing mixed culture biocathodes had complex bacterial biofilms variable in size and shape as observed by confocal and electron microscopy. Sequence analysis of ribosomal 16S rDNA revealed a putative correlation between the abundance of certain microbiota and biocathode performance. The best performing biocathode developed on the unmodified graphite electrode and reached a high current density for oxygen reducing biocathodes at neutral pH (0.9 A/m2). This correlated with the highest domination (60.7 %) of a monophyletic group of unclassified γ-Proteobacteria. These results corroborate earlier reports by other groups, however, higher current densities and higher presence of these unclassified bacteria were observed in this work. Therefore, members of this group are likely key-players for highly performing oxygen reducing biocathodes.
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- "Changing the parameters which mainly influence bacterialattachment, such as charge, hydrophobicity and roughness[61,62], can increase or decrease bacterial attachment and have found various specific applications (for example biomedical implants should inhibit bacterial attachment while, in some cases in biotechnology, the attachment of bacteria to a surface is desirable). The extensive literature in these areas reveals that changing surface parameters has different effects depending on the kind of bacteria. One of the surface parameters which has a drastic effect on bacterialadhesion is hydrophobicity of both the surface of cells and mate- rials. "
ABSTRACT: A novel rapid method for bacterial differentiation is explored based on the specific adhesion pattern of bacterial strains to tunable polymer surfaces. Different types of counter ions were used to electrochemically fabricate dissimilar polypyrrole (PPy) films with diverse physicochemical properties such as hydrophobicity, thickness and roughness. These were then modulated into three different oxidation states in each case. The dissimilar sets of conducting polymers were exposed to five different bacterial strains, Deinococcus proteolyticus, Serratia marcescens, Pseudomonas fluorescens, Alcaligenes faecalis and Staphylococcus epidermidis. By analysis of the fluorescent microscope images, the number of bacterial cells adhered to each surface were evaluated. Generally, the number of cells of a particular bacterial strain that adhered varied when exposed to dissimilar polymer surfaces, due to the effects of the surface properties of the polymer on bacterial attachment. Similarly, the number of cells that adhered varied with different bacterial strains exposed to the same surface, reflecting the different surface properties of the bacteria. Principal component analysis showed that each strain of bacteria had its own specific adhesion pattern. Hence, they could be discriminated by this simple, label-free method based on tunable polymer arrays combined with pattern recognition.
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- "Previous experimental studies have indicated the significance of bacterial motility mechanisms in the colonization process and the subsequent biofilm formation (O'Toole and Kolter 1998;Pratt and Kolter 1998;Watnick and Kolter 1999;Lemon et al. 2007;Merritt et al. 2007;Kim et al. 2008 ;Houry et al. 2010). In particular, flagellar mediated swimming is crucial in approaching the surface and initiating the adhesion process (Tuson and Weibel 2013) and pili-mediated motility highly promotes the surface exploration (Burrows 2012). The swimming capability of a subpopulation of cells endures even after the establishment of the biofilm structure. "
ABSTRACT: We numerically study the effect of solid boundaries on the swimming behavior of a motile microorganism in viscoelastic media. Understanding the swimmer-wall hydrodynamic interactions is crucial to elucidate the adhesion of bacterial cells to nearby substrates which is precursor to the formation of the microbial biofilms. The microorganism is simulated using a squirmer model that captures the major swimming mechanisms of potential, extensile, and contractile types of swimmers, while neglecting the biological complexities. A Giesekus constitutive equation is utilized to describe both viscoelasticity and shear-thinning behavior of the background fluid. We found that the viscoelasticity strongly affects the near-wall motion of a squirmer by generating an opposing polymeric torque which impedes the rotation of the swimmer away from the wall. In particular, the time a neutral squirmer spends at the close proximity of the wall is shown to increase with polymer relaxation time and reaches a maximum at Weissenberg number of unity. The shear-thinning effect is found to weaken the solvent stress and therefore, increases the swimmer-wall contact time. For a puller swimmer, the polymer stretching mainly occurs around its lateral sides, leading to reduced elastic resistance against its locomotion. The neutral and puller swimmers eventually escape the wall attraction effect due to a releasing force generated by the Newtonian viscous stress. In contrast, the pusher is found to be perpetually trapped near the wall as a result of the formation of a highly stretched region behind its body. It is shown that the shear-thinning property of the fluid weakens the wall-trapping effect for the pusher squirmer.
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