TY - CONF A1 - Kastanias, Elaine A1 - Özcan Sandikcioglu, Özlem T1 - Chemical interaction mechanisms of metal reducing bacteria on gold surfaces N2 - Bacterial biofilms represent a ubiquitous form of microbial life on Earth. Due to an evolved armory of protean biological responses to external stimuli, bacteria are able to adhere to, colonize and thrive on virtually all surfaces, whether natural or synthetic, even in challenging environmental conditions. In addition to significant health risks, biofilms are among the salient contributors to the deterioration of metals and their alloys, thereby causing safety risks for technical equipment. Hence, understanding the interaction mechanisms of electroactive sessile bacteria with metal surfaces is vital for facilitating the development of efficient control strategies and novel anti-fouling surfaces in various industries and technologies. The present study focusses on a combined spectroelectrochemical approach, melding methods of surface enhanced Raman spectroscopy (SERS) and electrochemical techniques, to investigate the chemical characteristics and redox activities of electroactive bacteria during the initial stages of biofilm formation. Gold has been selected as a model substrate due to its inert character, considerably high surface enhancement factor, as well as its capability to allow surface chemistry modifications and substrate polarization in order to precisely control the surface charge. Square wave voltammetry (SWV) and cyclic voltammetry (CV) studies have been performed for quantitative determination of flavin concentration and electrochemical impedance spectroscopy (EIS) has been utilized to study the changes in electrochemical processes within biofilms during different stages of growth. Shewanella sp. have been chosen as microorganisms within this work due to their versatile exoelectrogenic respiratory behavior and their distinct ability to reduce metals via extracellular electron transfer mechanisms involving self-secreted electron shuttle redox molecules such as flavins. To further explicate the process of diffusion of flavins within biofilms, a model system has been developed to simulate the structural features of the bacterial extracellular polymeric substances typically found in biofilms. This has been achieved by creating hydrogel films comprised of calcium-cross-linked alginate. The results demonstrate an interplay of factors contributing to the initial phases of bacterial settlement and biofilm formation as a function of environmental parameters. Furthermore, the results allow insight into the diffusion of flavins, much like they would in a natural biofilm, and how their redox behavior affects the biofilm development. T2 - 232nd ECS Meeting CY - National Harbor, MD, USA DA - 01.10.2017 KW - Biofilms KW - Electrochemistry KW - Microbiology KW - Bacterial Extracellular Electron Transfer Mechanisms KW - Surface Enhanced Raman Spectroscopy KW - Spectroelectrochemical Techniques KW - Biocorrosion PY - 2017 AN - OPUS4-47248 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kastanias, Elaine A1 - Özcan Sandikcioglu, Özlem T1 - Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces N2 - Bacterial biofilms are considered one of the salient contributing factors to the deterioration of metals and their alloys, occurring in virtually all environments and across various industrial systems. Considering the sheer magnitude of detrimental effects, it is of pertinent interest to elucidate the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces to facilitate the development of efficient antifouling strategies. A common constituent of microbial communities within aquatic and sedimentary settings, the Shewanella genus consists of facultatively aerobic, Gram-negative bacterium which exhibit exceptional plasticity in respiratory capacities. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor; conversely, under anaerobic conditions, it is able to undertake respiration by reducing alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms not yet thoroughly discerned. The aim of this work is to explicate the mechanisms governing the initial bacterial adhesion and subsequent biofilm formation on metallic surfaces. To investigate this dynamic interplay, a combined approach has been followed which couples surface enhanced Raman spectroscopy (SERS) with electrochemical techniques using Shewanella sp. model biofilms. Gold nano-islands deposited on thin glass slides have been chosen as inert model substrates with good uniformity and high surface enhancement factor. Furthermore, the utilization of gold as substrate material not only allowed the differentiation of the sole effect of substrate polarization on bacterial attachment but also enabled a precise adjustment of the surface chemistry and surface energy by means of surface functionalization with organothiol self-assembled monolayers. The results present the correlation of the primary settlement rate of bacteria on metallic substrates with the environmental parameters such as electrolyte composition and pH as well as surface-related properties like hydrophobicity/hydrophilicity and polarization. With the overall strategic goal of transferring this methodology to technical systems the results provide the fundamental basis for the bottom-up design of anti-fouling surfaces. T2 - Electrochemistry 2016 CY - Goslar, Germany DA - 26.09.2016 KW - Biofilms KW - Electrochemistry KW - Microbiology KW - Bacterial Extracellular Electron Transfer Mechanisms KW - Surface Enhanced Raman Spectroscopy KW - Spectroelectrochemical Techniques KW - Biocorrosion PY - 2016 AN - OPUS4-47249 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kastanias, Elaine A1 - Elert, Anna Maria A1 - Sturm, Heinz A1 - Özcan Sandikcioglu, Özlem T1 - Chemical and electrochemical interaction mechanisms of metal-reducing bacteria with gold surfaces N2 - The ubiquity of biofilms is accompanied by significant health and safety risks. Clarifying the interaction mechanisms of sessile bacteria with metal and metal oxide surfaces is of great interest to advance the development of new control strategies and novel anti-fouling surfaces which mitigate the detrimental effects of bio-fouling. The Shewanella genus is a faculatively aerobic, Gram-negative, exoelectrogenic bacterium known to demonstrate exceptional adaptability in respiratory capacities. Shewanella is often found in microbial communities within aquatic and sedimentary settings. During aerobic conditions, Shewanella utilizes oxygen as a terminal electron acceptor. During anaerobic conditions, respiration occurs via reduction of alternative terminal electron acceptors such as oxidized metals via extracellular electron transfer mechanisms involving electron shuttle molecules released by the bacteria. The purpose of this work is to investigate the mechanisms of bacterial attachment and subsequent biofilm formation on metallic surfaces. Using Shewanella sp. model biofilms, surface enhanced Raman spectroscopy (SERS) complemented with electrochemical techniques have been utilized to study this dynamic interaction. Additionally, to study the process of diffusion of extracellular electron shuttles, a model system comprised of calcium cross-linked alginate to mimic the architecture of bacterial extracellular polymeric substances has been used. Inert model substrates with consistent uniformity and high surface enhancement factor have been fabricated via the deposition of gold nano-islands on thin glass slides. Moreover, it has permitted modification of the surface chemistry and surface energy via surface functionalization using organothiol self-assembled monolayers. The presentation will summarize our results on the interplay between the initial settlement rate and biofilm formation kinetics of bacteria on metallic substrates with variable environmental conditions such as electrolyte composition, pH, in addition to surface characteristics such as hydrophobicity/hydrophilicity and external polarization. T2 - EUROCORR 2017 & 20thICC CY - Praha, Czech Republic DA - 04.09.2017 KW - Surface Enhanced Raman Spectroscopy (SERS) KW - Metal Reducing Bacteria (MRB) KW - Electron transfer PY - 2017 AN - OPUS4-43421 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -