Abstract
Quorum sensing (QS) is a central mechanism for regulating bacterial social networks in biofilm via the production of diffusible signal molecules (autoinducers). In this work, we assess the contribution of QS autoinducers to microbial extracellular electron transfer (EET) by Pseudomonas aeruginosa strain PAO1 and three mutants pure culture-inoculated in microbial electrolysis cells (MECs) and microbial fuel cells (MFCs). MECs inoculated with different P. aeruginosa strains showed a difference in current generation. All MFCs reached a reproducible cycle of current generation, and PQS-deficient pqsA mutant inoculated-MFCs obtained a much higher current generation than pqsL mutant inoculated-MFCs which overproduced PQS. lasIrhlI-inoculated MFCs produced a lower power output than others, as the strain was deficient in rhl and las. Exogenous N-butanoyl-l-homoserine lactone could remedy the electricity production by lasIrhlI mutants to a level similar to wild-type strains while signaling molecules had little effect on wild-type bacteria in MFCs. Meanwhile, experiments with the wild-type and pqsA, pqsL mutants indicated that the overexpression of PQS signaling molecules made no significant contribution to EET. QS signaling molecules therefore have dual-edged effects on microbial EET. These findings will provide favorable suggestions on the regulation of EET, but detailed QS regulatory mechanisms for extracellular electron transfer in pure- and mixed-cultures are yet to be elucidated.
Highlights
Microbial electrochemical systems (MESs) are a versatile group of technologies with the potential to achieve sustainable bioenergy generation, biosensing and bioelectrosynthesis using organic or inorganic carbon sources (Liu et al, 2016)
All strains were routinely cultivated in Luria–Bertani (LB) medium with shaking at 37◦C. 0.5 mL of overnight cultures were inoculated in 50 mL fresh LB medium for subsequent inoculation in single-chamber microbial fuel cells (MFCs) and microbial electrolysis cells (MECs)
MECs inoculated with different P. aeruginosa strains showed a difference in current generation (Figure 2A)
Summary
Microbial electrochemical systems (MESs) are a versatile group of technologies with the potential to achieve sustainable bioenergy generation, biosensing and bioelectrosynthesis using organic or inorganic carbon sources (Liu et al, 2016). The optimal reactor configurations, operating conditions and electrode materials for increased electron transfer in MES have been described previously (Rinaldi et al, 2008; Karthikeyan et al, 2015; Logan et al, 2015; Mei et al, 2015; Xing et al, 2015; Zou et al, 2016; Bi et al, 2018). Further improvement of electron transfer in MES is difficult due to inadequate understanding of electrodebiofilm formation in EAB. Low efficiency electron transfer at the anodic biofilm-electrode interface. Manipulating exoelectrogenic biofilms to improve the efficiency of the electron transfer pathway is a feasible strategy to improve MES performance
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