In Situ to in Silico and Back: Elucidating the Physiology and Ecology of Geobacter spp. Using Genome-Scale Modelling

There is a wide diversity of unexplored metabolism encoded in the genomes of microorganisms that have an important environmental role. Genome-scale metabolic modelling enables the individual reactions that are encoded in annotated genomes to be organized into a coherent whole, which can then be used to predict metabolic fluxes that will optimize cell function under a range of conditions. In this Review, we summarize a series of studies in which genome-scale metabolic modelling of Geobacter spp. has resulted in an in-depth understanding of their central metabolism and ecology. A similar iterative modelling and experimental approach could accelerate elucidation of the physiology and ecology of other microorganisms inhabiting a diversity of environments, and could guide optimization of the practical applications of these species

Microbial ecology meets electrochemistry: electricity driven and driving communities

Bio-electrochemical systems (BESs) have recently emerged as an exciting technology. In a BES, bacteria interact with electrodes using electrons, which are either removed or supplied through an electrical circuit. The most-described type of BES is microbial fuel cells (MFCs), in which useful power is generated from electron donors as, for example, present in wastewater. This form of charge transport, known as extracellular electron transfer, was previously extensively described with respect to metals such as iron and manganese. The importance of these interactions in global biogeochemical cycles is essentially undisputed. A wide variety of bacteria can participate in extracellular electron transfer, and this phenomenon is far more widespread than previously thought. The use of BESs in diverse research projects is helping elucidate the mechanism by which bacteria shuttle electrons externally. New forms of interactions between bacteria have been discovered demonstrating how multiple populations within microbial communities can co-operate to achieve energy generation. New environmental processes that were difficult to observe or study previously can now be simulated and improved via BESs. Whereas pure culture studies make up the majority of the studies performed thus far, even greater contributions of BESs are expected to occur in natural environments and with mixed microbial communities. Owing to their versatility, unmatched level of control and capacity to sustain novel processes, BESs might well serve as the foundation of a new environmental biotechnology. While highlighting some of the major breakthroughs and addressing only recently obtained data, this review points out that despite rapid progress, many questions remain unanswered

Anaerobes in Bioelectrochemical Systems

In bioelectrochemical systems (BES), the catalytic activity of anaerobic microorganisms generates electrons at the anode which can be used, for example, for the production of electricity or chemical compounds. BES can be used for various purposes, including wastewater treatment, production of electricity, fuels and chemicals, biosensors, bioremediation, and desalination. Electrochemically active microorganisms are widely present in the environment and they can be found, in sediment, soil, compost, wastewaters and their treatment plants. Exoelectrogens are microorganisms capable of donating electrons to anode electrode or accepting electrons from cathode electrode and are mainly responsible for current generation or use in BES. However, current generation from fermentable substrates often requires the presence of electrochemically inactive microorganisms that break down complex substrates into metabolites which can be further utilized by exoelectrogens. The growth and electron transfer efficiency of anaerobes depend on several parameters, such as system architecture, electrode material and porosity, electrode potential and external resistance, pH, temperature, substrate concentration, organic loading rate, and ionic strength. In this chapter, the principles and microbiology of bioelectrochemical systems as well as selective factors for exoelectrogens are reviewed. The anaerobic microorganisms and their electron transfer mechanisms at the anode and cathode are described and future aspects are briefly discussed.acceptedVersionNon peer reviewe