Bioelectrochemical Techniques Research Articles

Electric Fields at the Lipid Membrane Interface.

This review presents a comprehensive analysis of electric field distribution at the water-lipid membrane interface in the context of its relationship to various biochemical problems. The main attention is paid to the methodological aspects of bioelectrochemical techniques and quantitative analysis of electrical phenomena caused by the ionization and hydration of the membrane-water interface associated with the phase state of lipids. One of the objectives is to show the unique possibility of controlling changes in the structure of the lipid bilayer initiated by various membrane-active agents that results in electrostatic phenomena at the surface of lipid models of biomembranes-liposomes, planar lipid bilayer membranes (BLMs) and monolayers. A set of complicated experimental facts revealed in different years is analyzed here in order of increasing complexity: from the adsorption of biologically significant inorganic ions and phase rearrangements in the presence of multivalent cations to the adsorption and incorporation of pharmacologically significant compounds into the lipid bilayer, and formation of the layers of macromolecules of different types.

Microbially catalyzed enhanced bioelectrochemical performance using covalent organic framework–modified cathode in a microbial electrosynthesis system

Electrode modification plays a critical role in enhancing the bioelectrochemical performance of a microbial electrosynthesis system (MES). This study involved the modification of the conventional carbon felt (CF) electrode through in situ covalent grafting with a covalent organic framework (TpPa-COF). Subsequently, the performance of this modified electrode was assessed as a cathode in MES. Various physical and bioelectrochemical techniques, such as chronoamperometry, cyclic voltammetry, and electrochemical spectroscopy, demonstrated the remarkable stability, reduced electrode resistance, increased current density, and superior bioelectrochemical activity of the modified electrode. The application of COF@CF caused a 3.2-fold improvement in current density, leading to an enhanced production of volatile fatty acids. The rough surface of the COF@CF electrode and its abundant catalytically active sites facilitated the growth of microorganisms, particularly exoelectrogenic and fermentative genera such as Desulfitobacterium, Clostridium, and Desulfovibrio. These findings highlight the promising potential of COF@CF in various bioelectrochemical applications.

Energy generation from bioelectrochemical techniques: Concepts, reactor configurations and modeling approaches

The process industries play a significant role in boosting the economy of any nation. However, poor management in several industries has been posing worrisome threats to an environment that was previously immaculate. As a result, the untreated waste and wastewater discarded by many industries contain abundant organic matter and other toxic chemicals. It is more likely that they disrupt the proper functioning of the water bodies by perturbing the sustenance of many species of flora and fauna occupying the different trophic levels. The simultaneous threats to human health and the environment, as well as the global energy problem, have encouraged a number of nations to work on the development of renewable energy sources. Hence, bioelectrochemical systems (BESs) have attracted the attention of several stakeholders throughout the world on many counts. The bioelectricity generated from BESs has been recognized as a clean fuel. Besides, this technology has advantages such as the direct conversion of substrate to electricity, and efficient operation at ambient and even low temperatures. An overview of the BESs, its important operating parameters, bioremediation of industrial waste and wastewaters, biodegradation kinetics, and artificial neural network (ANN) modeling to describe substrate removal/elimination and energy production of the BESs are discussed. When considering the potential for use in the industrial sector, certain technical issues of BES design and the principal microorganisms/biocatalysts involved in the degradation of waste are also highlighted in this review.

Complete pentachlorophenol biodegradation in a dual-working electrode bioelectrochemical system: Performance and functional microorganism identification

Bioelectrochemical system (BES) can effectively promote the reductive dechlorination of chlorophenols (CPs). However, the complete degradation of CPs with sequential dechlorination and mineralization processes has rarely achieved from the BES. Here, a dual-working electrode BES was constructed and applied for the complete degradation of pentachlorophenol (PCP). Combined with DNA-stable isotope probing (DNA-SIP), the biofilms attached on the anodic and cathodic electrode in the BES were analyzed to explore the dechlorinating and mineralizing microorganisms. Results showed that PCP removal efficiency in the dual-working BES (84% for 21 days) was 4.1 and 4.7 times higher than those of conventional BESs with a single anodic or cathodic working electrode, respectively. Based on DNA-SIP and high-throughput sequencing analysis, the cathodic working electrode harbored the potential dechlorinators (Comamonas, Pseudomonas, Methylobacillus, and Dechlorosoma), and the anodic working enriched the potential intermediate mineralizing bacteria (Comamonas, Stenotrophomonas, and Geobacter), indicating that PCP could be completely degraded under the synergetic effect of these functional microorganisms. Besides, the potential autotrophic functional bacteria that might be involved in the PCP dechlorination were also identified by SIP labeled with 13C-NaHCO3. Our results proved that the dual-working BES could accelerate the complete degradation of PCP and enrich separately the functional microbial consortium for the PCP dechlorination and mineralization, which has broad potential for bioelectrochemical techniques in the treatment of wastewater contaminated with CPs or other halogenated organic compounds.

Advances in Cancer Diagnosis: Bio-Electrochemical and Biophysical Characterizations of Cancer Cells.

Cancer is a worldwide leading cause of death, and it is projected that newly diagnosed cases globally will reach 27.5 million each year by 2040. Cancers (malignant tumors), unlike benign tumors are characterized by structural and functional dedifferentiation (anaplasia), breaching of the basement membrane, spreading to adjacent tissues (invasiveness), and the capability to spread to distant sites (metastasis). In the cancer biology research field, understanding and characterizing cancer metastasis as well as features of cell death (apoptosis) is considered a technically challenging subject of study and clinically is very critical and necessary. Therefore, in addition to the cytochemical methods traditionally used, novel biophysical and bioelectrochemical techniques (e.g., cyclic voltammetry and electrochemical impedance spectroscopy), atomic force microscopy, and electron microscopic methods are increasingly being deployed to better understand these processes. Implementing those methods at the preclinical level enables the rapid screening of new anticancer drugs with understanding of their central mechanism for cancer therapy. In this review, principles and basic concepts of new techniques suggested for metastasis, and apoptosis examinations for research purposes are introduced, along with examples of each technique. From our recommendations, the privilege of combining the bio-electrochemical and biosensing techniques with the conventional cytochemical methods either for research or for biomedical diagnosis should be emphasized.

Microbially catalyzed enhanced bioelectrochemical performance using covalent organic framework‐modified anode in a microbial fuel cell

Electrode modification is crucial in improving the power density and bioelectrochemical performance of a microbial fuel cell (MFC). The conventional carbon felt (CF) surface was modified as an anode in this study to examine an emerging class of materials known as covalent organic framework (COF). In a three-electrode system, the performance of the modified anode (TpPa-1@CF) was evaluated using various physical and bioelectrochemical techniques, demonstrating superior bioelectrochemical activity (cyclic voltammetry), reduced electrode resistance (electrochemical spectroscopy), and excellent electrode stability (chronoamperometry). With a 4.3 and 12.7-fold improvement in power (1069 mW/m2) and current (1954 mA/m2) density and steady MFC performance as compared to the uncoated electrode throughout five MFC cycles, TpPa-1@CF demonstrated better bioelectrochemical activity. Furthermore, the rough electrode surface area and numerous catalytically active sites of TpPa-1@CF promoted the microbial growth/adhesion along with substrate fluxes yielding the selective enrichment of Proteobacteria and Bacteroidetes (electricity-producing phyla). These results indicated that TpPa-1@CF is a promising anode material for several bioelectrochemical applications.

Evaluation of Cytotoxic Effect of Nystatin on Yeast Cells By Electrochemical Monitoring of Intracellular NADH with Double Mediator System

Background and purpose Environmental safety concern needs in medical diagnosis and food test to rapidly identify pathogenic organisms and their susceptibilities to medical agents and toxic chemicals have encouraged to develop more easy and precise new diagnostic methods. Bio-electrochemical techniques are very convenient and useful for monitoring cell viability, the identification of intracellular function and understanding the biological process [1-5]. NAD+ /NADH is a crucial cofactor for enzymatic reaction and ATP production in cytosol and mitochondria. This biomaterial is one of the most important markers for sensing these mentioned processes.Recently, we have proposed a rapid and sensitive bio-electrochemical method for yeast cell counting in broader range as compared with conventional optical method through the monitoring of intracellular NADH by using a double mediator system with a screen-printed carbon electrode (SPCE). Now by applying this method, we have succeeded to evaluate the fast-acting toxicity of nystatin (NYT) at very lower concentration on yeast cell. Near future this method could be also applicable to the bacterial cell viability. Experimental method Fission yeast Schizosaccharomyces pombe cell suspension with HBSS was taken in each well of 96 well plates and final conc. of 500 μM potassium ferricyanide and 10 μM 1-mPMS solution were added in a drop wise to the cell suspension. After incubation for 10 minutes, SPCE was vertically immersed into the cell suspension and chronoamperometric measurement was immediately performed by potential application at +0.5V. Prior to the electrochemical measurement, yeast cell was grown in YE medium (0.5% Difco yeast extract and 3% glucose) supplemented with 150 µg/mL leucine to a density of cells/ml at 30 [6]. After culturing the cell, the optical density of cell suspension was measured at 592 nm to estimate the number of yeast cells. The cells were washed with HBSS and adjusted to the desired concentration. Result and discussion The oxidation current was measured in each yeast cell suspension by chronoamperometry of ferrocyanide generated by intracellular NADH with redox mediation of 1-mPMS. Fig.1 and Fig.2 shows that the decrease of oxidation current was clearly dependent on the concentration of NYT (final conc. was 1, 2, 4, 8, 16, 32 mg/mL). It was indicated that intracellular NADH level corresponding to the cell viability was rapidly decreased by NYT effect. On the other hand, we have also investigated the toxic effect of NYT by double staining (SYT09 + PI) fluorescence method. Generally, NYT forms a pore-like structure on the cell membrane and thereby the integrity of the cell membrane is lost [7]. Though NYT caused disruption of fungal cell membrane at higher concentration but at very lower concentration PI could not enter into the cell and therefore PI staining was not occurred. That means, in this method no effect was observed (data will be shown in the conference). In electrochemical method, the cell viability decreased at very lower concentration maybe due to apoptotic pathway or the inhibition of unspecific enzyme by NYT inside of yeast cell but not for the disruption of cell membrane. It was now considered that NYT to the cells with pore formation in cell membranes is the secondary inhibitory mechanism and the primarily action may be due to intracellular oxidative damage and interaction with organelles [7].Though evaluation of nystatin effect at very low concentration was not possible by the double staining method but it was possible to detect it by our electrochemical method. References 1) A. Heiskanen, J. Yakovleva, C. Spégel, R. Taboryski, M. Koudelka-Hep, J. Emnéus, T. Ruzgas, ElectrochemCommun, 6 (2004) 219-224.2) A. Heiskanen, C. Spégel, N. Kostesha, S. Lindahl, T. Ruzgas J. Emnéus, AnalBiochem, 384 (2009) 11-19.3) R.Y.A. Hassan, U. Bilitewski, Anal Biochem, 419 (2011) 26-32.4) M. Rahimi, H.Y. Youn, D.J. McCanna, J.G. Sivak, S.R. Mikkelsen, Anal Bioanal Chem, 405 (2013) 4975-4979.5) Y. Matsumae, Y. Takahashi, K. Ino, H. Shiku, T. Matsue, Anal Chim Acta, 842 (2014) 20-26.6) Minoru Suga, Aya Kunimoto, Hiroaki Shinohara, Biosensors and Bioelectronics, 97(2017), 53-58.7)Serhan G, Stack CM, Perrone GG, Morton CO. 2014. Ann. Clin. Microbiol. Antimicrob. 13: 18. Figure 1

State-of-Art Bio-Assay Systems and Electrochemical Approaches for Nanotoxicity Assessment.

Innovations in the field of nanotechnology, material science and engineering has rendered fruitful utilities in energy, environment and healthcare. Particularly, emergence of surface engineered nanomaterials offered novel varieties in the daily consumables and healthcare products including therapeutics and diagnostics. However, the nanotoxicity and bioactivity of the nanomaterials upon interaction with biological system has raised critical concerns to individual as well as to the environment. Several biological models including plant and animal sources have been identified to study the toxicity of novel nanomaterials, correlating the physio-chemical properties. Biological interaction of nanomaterials and its mediated physiological functions are studied using conventional cell/molecular biological assays to understand the expression levels of genetic information specific to intra/extra cellular enzymes, cell viability, proliferation and function. However, modern research still demands advanced bioassay methods to screen the acute and chronic effects of nanomaterials at the real-time. In this regard, bioelectrochemical techniques, with the recent advancements in the microelectronics, proved to be capable of providing non-invasive measurement of the nanotoxicity effects (in vivo and in vitro) both at single cellular and multicellular levels. This review attempted to provide a detailed information on the recent advancements made in development of bioassay models and systems for assessing the nanotoxicology. With a short background information on engineered nanomaterials and physiochemical properties specific to consumer application, present review highlights the multiple bioassay models evolved for toxicological studies. Emphasize on multiple mechanisms involved in the cell toxicity and electrochemical probing of the biological interactions, revealing the cytotoxicity were also provided. Limitations in the existing electrochemical techniques and opportunities for the future research focusing the advancement in single molecular and whole cell bioassay has been discussed.

Influence of Incubation Temperature on 9,10-Anthraquinone-2-Sulfonate (AQS)-Mediated Extracellular Electron Transfer.

The electron shuttling process has been recognized as an important microbial respiration process. Because the incubation temperature can influence both the reactivity of electron mediators and cell growth, it may also affect the electron-shuttle-mediated extracellular electron transfer (EET) process. Here, the effect of incubation temperature (22–38°C) was investigated in a bioelectrochemical system (BES) using Shewanella oneidensis MR-1 and 50 μM of 9,10-anthraquinone-2-sulfonate (AQS). We found that current generation increased as the temperature was increased from 22 to 34°C and then decreased sharply at 38°C. The biofilm biomass, as indicated by the total protein extracted from the electrode, increased as the temperature increased from 22 to 34°C and then decreased at 38°C, mirroring the current generation results. These results were further confirmed by increasing the temperature slowly, step-by-step, in a single BES with a constant biofilm biomass, suggesting that the EET rates could be substantially influenced by temperature, even with the same biofilm. The effects of temperature on the AQS bioreduction rate, c-type cytochrome (c-Cyts)-bound-cofactor-mediated EET, the AQS mid-point potential, and the AQS diffusion coefficient were studied. From these results, we were able to conclude that temperature influenced the EET rates by changing the c-Cyts-bound-cofactor-mediated EET process and the AQS bioreduction rate, and that the change in biofilm formation was a dominant factor influencing the overall EET rates. These findings should contribute to the fundamental understanding of EET processes. Moreover, optimization of the operating parameters for current generation will be helpful for the practical application of bioelectrochemical techniques.

Electro-Microbiology as a Promising Approach Towards Renewable Energy and Environmental Sustainability

Microbial electrochemical technologies provide sustainable wastewater treatment and energy production. Despite significant improvements in the power output of microbial fuel cells (MFCs), this technology is still far from practical applications. Extracting electrical energy and harvesting valuable products by electroactive bacteria (EAB) in bioelectrochemical systems (BESs) has emerged as an innovative approach to address energy and environmental challenges. Thus, maximizing power output and resource recovery is highly desirable for sustainable systems. Insights into the electrode-microbe interactions may help to optimize the performance of BESs for envisioned applications, and further validation by bioelectrochemical techniques is a prerequisite to completely understand the electro-microbiology. This review summarizes various extracellular electron transfer mechanisms involved in BESs. The significant role of characterization techniques in the advancement of the electro-microbiology field is discussed. Finally, diverse applications of BESs, such as resource recovery, and contributions to the pursuit of a more sustainable society are also highlighted.

Electrotrophic activity and electrosynthetic acetate production by Desulfobacterium autotrophicum HRM2

Electroautotrophic microorganisms accept electrons from a cathode as source of reducing equivalents to drive CO2 fixation by poorly understood mechanisms. Acetogenic bacteria were the first group found to possess the capability for electroautotrophic metabolism in pure culture with associated electrosynthesis of acetate as primary metabolite. Identification of additional electrotrophic species can contribute to our understanding of this unusual form of metabolism. Here, bioelectrochemical techniques, chemical analysis and microscopy were used to determine electrotrophic metabolism of Desulfobacterium autotrophicum HRM2. Chronoamperometry showed increasing current uptake over 21 days of incubation in duplicate bioelectrochemical system sets. Linear sweep voltammetry indicated peak current uptake at −243 mV. High performance liquid chromatography (HPLC) analysis quantified acetate accumulation in anaerobic minimal media containing inorganic carbon as sole carbon source, consistent with electrosynthesis. Scanning electron microscopy and live/dead staining by epifluorescence microscopy analysis indicated viable 1–2 μm cells after 76 days of cultivation under electroautotrophic conditions. The genome of Db. autotrophicum HRM2 is fully sequenced and, thus, could provide insight into the biochemical and physiological mechanisms by which electrotrophic cells utilize cathode-derived electrons. This research expands the diversity of facultative autotrophs capable of electrotrophic metabolism to include the sulfate-reducing marine bacterium Db. autotrophicum HRM2.

Research Progress in Detection of Malignant Hematologic Diseases by Bio-electrochemistry -Review

Hematologic disease has become a common disease that produces harm and burdens to human individuals today, seriously threatening public health care. Particularly, the damage caused by malignant hematologic disease has been recognized by doctors and patients. However, low cure rate and high recurrence rate are the main issues when treating malignant hematologic disease by current methods. The survival rate could be significantly improved if the early metaphase diagnosis rate could be improved. Therefore, early diagnosis is important for malignant hematologic disease at molecular level. In recent years, the bio-electrochemical method for tumor cells and blood detection has attracted more and more attention. Because many cancer cell surface proteins are important biomarkers, changing in the surface proteins'quantity and condition as well as a variety of electrophysiological activity often show some potential diseases. Each cancer cell has a specific biomarker to distinguish it from the normal cell line. As a result, their biomarkers can be detected by bioelectrochemical techniques. Therefore, it provides theoretical and experimental support for detecting the cancer cell activity, diagnosis and treatment of diseases, and screening the drugs. In recent years, the development of biosensor, nanotechnology, probe and electrode, as well as Lab-on-a-chip has contributed a lot to the development of bioelectrochemistry, especially the development of the inspection and drug resistance in hematological and oncological diseases. This review lists the different composition of bio-electrochemical technology, focusing on the progress in hematologic field so as to put forward the research.

Microbial Fuel Cells and Their Applications for Cost Effective Water Pollution Remediation

A recent research in the field of microbial fuel cell (MFC) is exploring bio-electrochemical processes to generate electricity. Fundamentals to microbial fuel cell are proper cost effective cell design, electrodes, substrates, proton exchange membranes and bacterial species forming biofilms on electrode. The MFC is considered to be specific for current generation by bacterial metabolism. The current review uncovers the fact that MFC technology is not only for the current generation but is also effective for bio-remediation, bio-sensors and for biosynthesis of valuable organic products. Industrial and domestic wastes are pollutants, toxic for health and environment. Their chemical treatment itself requires expensive chemicals which in turn lead to other composites in the environment. The cost effective and safe technique has been employed for remediation like catalytically active bio-electrodes in MFC. The exoelectrogens are capable of electron transfer by forming conductive biofilms on the solid surfaces of electrodes. The Geobacter, Shewanella and Sporomusa species have the tendency to form nanowires or have C-type cytochromes for electron conduction. The redox capability of these electro active biofilms is not only to reduce the hazardous materials but also to catalyze the electrochemical reactions like corrosion alleviation, biosensor development, bio-remediation and biochemical synthesis. These bio-electrochemical techniques have been proved to be the best for low cost, high catalytic activity, less pollution and no secondary contaminants.

Microbial electron transport and energy conservation - the foundation for optimizing bioelectrochemical systems.

Microbial electrochemical techniques describe a variety of emerging technologies that use electrode–bacteria interactions for biotechnology applications including the production of electricity, waste and wastewater treatment, bioremediation and the production of valuable products. Central in each application is the ability of the microbial catalyst to interact with external electron acceptors and/or donors and its metabolic properties that enable the combination of electron transport and carbon metabolism. And here also lies the key challenge. A wide range of microbes has been discovered to be able to exchange electrons with solid surfaces or mediators but only a few have been studied in depth. Especially electron transfer mechanisms from cathodes towards the microbial organism are poorly understood but are essential for many applications such as microbial electrosynthesis. We analyze the different electron transport chains that nature offers for organisms such as metal respiring bacteria and acetogens, but also standard biotechnological organisms currently used in bio-production. Special focus lies on the essential connection of redox and energy metabolism, which is often ignored when studying bioelectrochemical systems. The possibility of extracellular electron exchange at different points in each organism is discussed regarding required redox potentials and effect on cellular redox and energy levels. Key compounds such as electron carriers (e.g., cytochromes, ferredoxin, quinones, flavins) are identified and analyzed regarding their possible role in electrode–microbe interactions. This work summarizes our current knowledge on electron transport processes and uses a theoretical approach to predict the impact of different modes of transfer on the energy metabolism. As such it adds an important piece of fundamental understanding of microbial electron transport possibilities to the research community and will help to optimize and advance bioelectrochemical techniques.

Identifying target processes for microbial electrosynthesis by elementary mode analysis.

BackgroundMicrobial electrosynthesis and electro fermentation are techniques that aim to optimize microbial production of chemicals and fuels by regulating the cellular redox balance via interaction with electrodes. While the concept is known for decades major knowledge gaps remain, which make it hard to evaluate its biotechnological potential. Here we present an in silico approach to identify beneficial production processes for electro fermentation by elementary mode analysis. Since the fundamentals of electron transport between electrodes and microbes have not been fully uncovered yet, we propose different options and discuss their impact on biomass and product yields.ResultsFor the first time 20 different valuable products were screened for their potential to show increased yields during anaerobic electrically enhanced fermentation. Surprisingly we found that an increase in product formation by electrical enhancement is not necessarily dependent on the degree of reduction of the product but rather the metabolic pathway it is derived from. We present a variety of beneficial processes with product yield increases of maximal 36% in reductive and 84% in oxidative fermentations and final theoretical product yields up to 100%. This includes compounds that are already produced at industrial scale such as succinic acid, lysine and diaminopentane as well as potential novel bio-commodities such as isoprene, para-hydroxybenzoic acid and para-aminobenzoic acid. Furthermore, it is shown that the way of electron transport has major impact on achievable biomass and product yields. The coupling of electron transport to energy conservation could be identified as crucial for most processes.ConclusionsThis study introduces a powerful tool to determine beneficial substrate and product combinations for electro-fermentation. It also highlights that the maximal yield achievable by bio electrochemical techniques depends strongly on the actual electron transport mechanisms. Therefore it is of great importance to reveal the involved fundamental processes to be able to optimize and advance electro fermentations beyond the level of lab-scale studies.Electronic supplementary materialThe online version of this article (doi:10.1186/s12859-014-0410-2) contains supplementary material, which is available to authorized users.

In silico characterization of microbial electrosynthesis for metabolic engineering of biochemicals

BackgroundA critical concern in metabolic engineering is the need to balance the demand and supply of redox intermediates such as NADH. Bioelectrochemical techniques offer a novel and promising method to alleviate redox imbalances during the synthesis of biochemicals and biofuels. Broadly, these techniques reduce intracellular NAD+ to NADH and therefore manipulate the cell's redox balance. The cellular response to such redox changes and the additional reducing power available to the cell can be harnessed to produce desired metabolites. In the context of microbial fermentation, these bioelectrochemical techniques can be used to improve product yields and/or productivity.ResultsWe have developed a method to characterize the role of bioelectrosynthesis in chemical production using the genome-scale metabolic model of E. coli. The results in this paper elucidate the role of bioelectrosynthesis and its impact on biomass growth, cellular ATP yields and biochemical production. The results also suggest that strain design strategies can change for fermentation processes that employ microbial electrosynthesis and suggest that dynamic operating strategies lead to maximizing productivity.ConclusionsThe results in this paper provide a systematic understanding of the benefits and limitations of bioelectrochemical techniques for biochemical production and highlight how electrical enhancement can impact cellular metabolism and biochemical production.

Rapid Bioelectrochemical Methods for the Detection of Living Microorganisms

Methods suitable for the estimation of microbial biomass are reviewed. Rapid bioelectrochemical techniques for detecting viable bacteria and yeasts were investigated using fuel cell and poised potential amperometric detectors. Escherichia coli in a fuel cell was detected over the range of 4x 106-4 x 109cells m-1, with an analysis .time of approximately 30min. The three electrode amperometric detector produced a linear calibration curve for Eschericha coIi in the range 6 x 106- 6 x 108cells m-1 The correlation coefficient was 0.996 (P < 0.001) and the analysis time <15 min. The two electrode amperometric system gave linear calibration for 5 x 106- 9 x 107 E.coli cells ml-1 The correlation coefficient was 0.999 (P <0.001) and the analysis time <15 min. Batch growth of several bacteria and a yeast was successfully monitored bioelectrochemically. It was concluded that the two electrode poised potential amperometric method provided rapid, convenient, inexpensive detection of a wide range of microorganisms.