Electrochemical sensing of aerobic marine bacterial biofilms and the influence of nitric oxide attachment control
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Electrochemical sensing of aerobic marine bacterial biofilms and the influence of nitric oxide attachment control Stéphane Werwinski1, Julian A. Wharton1, M. Debora Iglesias-Rodriguez2 and Keith R. Stokes1,3 1
National Centre for Advanced Tribology at Southampton (NCATS), School of Engineering Sciences, University of Southampton, Highfield, Southampton, SO17 1BJ, UK. 2
Ocean Biogeochemistry and Ecosystems, National Oceanography Centre, University of Southampton, Waterfront Campus, European Way, Southampton, SO14 3ZH, UK. 3
Physical Sciences Department, Dstl, Porton Down, Salisbury, Wiltshire, SP4 0JQ, UK.
ABSTRACT Suitable in situ techniques capable of sensing for the presence of a biofilm on metallic surfaces are becoming increasingly necessary, especially in order to maintain seawater pipe system performance. This study has investigated the detection of aerobic marine bacterial biofilms using electrochemical impedance spectroscopy by monitoring the interfacial response of Pseudoalteromonas sp. NCIMB 2021 attachment and growth in order to identify characteristic events on a 0.2 mm diameter gold electrode surface. Uniquely, the applicability of surface charge density has been proven to be valuable in determining biofilm attachment and cell enumeration over 72 h duration on a gold surface within a modified continuous culture flow cell (a controlled low laminar flow regime with a Reynolds number ≈ 1). In addition, the potential for biofilm disruption has been evaluated using 500 nM of the nitric oxide (NO) donor sodium nitroprusside (NO is important for the regulation of a number of diverse biological processes). Ex situ confocal microscopy studies were performed to confirm biofilm coverage and morphology, plus the determination and quantification of the NO biofilm dispersal effects. Overall, the capability of the sensor to electrochemically detect the presence of initial bacterial biofilm formation and extent has been established and shown to have potential for real-time biofilm monitoring. INTRODUCTION Marine bacteria are ubiquitous and are often reported to be primary colonizers on metallic surfaces in seawater and play a pivotal role in the initial biofilm development and also the maintenance of a biofouling community [1]. The engineering issues of this troublesome phenomenon in both naval applications and in merchant shipping are numerous and can cause excessive capital costs, e.g. in excess of £100k each to replace header castings [2] and heat exchanger costs of up to £300-£500 million per annum [3]. Biofilms and biofouling within seawater handling systems can affect the hydrodynamic properties (surface frictional resistance and cause flow restrictions) and reduce heat transfer performance of operating marine heat exchangers leading to frequent failures and blockages of components. Although the problems of biofouling in marine heat exchangers are abundant, reliable and accurate techniques capable of sensing for the presence and extent of biofilms on metallic surfaces are still required. Also, the proposed in
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