Evaluation of extracellular electron transfer in Pseudomonas aeruginosa by a novel co-expression of nicotinate mononucleotide adenyltransferase and quinolate phosphoribosyltransferase genes

Pseudomonas aeruginosa (PA) is an electrogenic bacterium, in which extracellular electron transfer (EET) is mediated by microbially-produced phenazines, especially pyocyanin. Increasing EET rate in electrogenic bacteria is key for the development of biosensors and bioelectrofermentation processes. In this work, the production of pyocyanin and Nicotinamide Adenine Dinucleotide (NAD) synthetase in the electrogenic strain PA-A4 is determined in microbial fuel cells (MFCs). The MFC potentials correlates with the NAD synthetase activity and with pyocyanin production. With the fusion and combined overexpression of nicotinic acid mononucleotide adenyltransferase (nadD) and quinolic acid phosphoribosyltransferase (nadC) genes, which are distant on the PA genomic map, faster co-transcription and increased NAD synthetase activity is enabled. The resulting PA-A4 nadD+nadC shows both increased pyocyanin concentration and MFC potential than the unmodified strain. Extracellular respiratory mechanisms in PA are linked with NAD metabolism, and targeted increased yield of NAD could directly lead to enhanced EET. However, this is the first report of electrogenicity enhancement in PA by fusion and combined overexpression of nadD and nadC genes.