Microbial Interactions in Electroactive Biofilms for Environmental Engineering Applications: A Role for Nonexoelectrogens

Abstract

Microbial electrochemical systems have gained much attention over the past decade due to their potential for various environmental engineering applications ranging from energy production to wastewater treatment to bioproduction. At the heart of these systems lie exoelectrogens−microorganisms capable of exporting electrons generated during metabolism to external electron acceptors such as electrodes. The bacterial biofilm communities on these electrodes are dominated by exoelectrogens but are nonetheless extremely diverse. So far, within the field, the main focus has been on the electroactive bacteria. However, to broaden our understanding of these communities, it is crucial to clarify how the remaining inhabitants of electrode-respiring biofilms contribute to the overall function of the biofilm. Ultimately, such insights may enable improvement of microbial electrochemical systems by reshaping the community structure with naturally occurring beneficial strains.

Molecular Insights into the Response of Nonelectroactive Bacteria to Electro-stimulation: Growth and Metabolism Regulation Mechanism

“…In recent decades, the spotlight has been on EAB proficient in extracellular electron transfer with electrodes, which are often considered as the linchpin of electro-biostimulation systems. Nevertheless, the biostimulation system is composed of a complete and dynamic community, with multiple niches required to be filled by non-EAB E.…”

“…Nevertheless, the biostimulation system is composed of a complete and dynamic community, with multiple niches required to be filled by non-EAB. 15 E. coli, a quintessential non-EAB, ubiquitously inhabits soil and water ecosystems, with its family representing up to one-third of a natural environment. 63 Due to the conservativeness of metabolic pathways, we also believe that the response behaviors and mechanisms obtained in this study are equally valid for the vast majority of bacteria in electro-biostimulation systems.…”

“…These non-EAB were either not equipped with extracellular electronic shuttle channels ( i.e. , some fermentative bacteria) or could not perform EET due to being far away from electrodes (planktonic microbes). − Interestingly, certain non-EAB could also make positive contributions to the synergetic removal of contaminants via either supplying simple substrates to EAB or performing independently. , Understanding whether and how these microbes respond to electro-stimulation is crucial for revealing the role of significant quantities of non-EAB in the electro-biostimulation systems.…”

Layered Design of a Highly Repeatable Electroactive Biofilm for a Standardized Biochemical Oxygen Demand Sensor

“…Interestingly, although the complex bacteria in wastewater randomly limited the current densities at the beginning of colonization, they enhanced current outputs once the electroactive SD-1 core was preformed. 32 Oxygen in the medium was not removed in the following cycles, and the current densities in the designed EABs (DEABs) were all stabilized at 2.5 ± 0.1 A/m 2 in five consecutive cycles, while that of natural EABs (NEABs, directly acclimated from wastewater) gradually decayed by 50% from 1.2 ± 0.6 to 0.6 ± 0.6 A/m 2 (n = 20, Figure 3C). DEABs exhibited excellent performance in fast adaptation to the intermittent exposure of oxygen compared to the continuous loss of current densities in NEABs.…”

“…Subsequently, the current density further rose by 37% to 2.6 ± 0.3 A/m 2 after introducing domestic wastewater. Interestingly, although the complex bacteria in wastewater randomly limited the current densities at the beginning of colonization, they enhanced current outputs once the electroactive SD-1 core was preformed . Oxygen in the medium was not removed in the following cycles, and the current densities in the designed EABs (DEABs) were all stabilized at 2.5 ± 0.1 A/m 2 in five consecutive cycles, while that of natural EABs (NEABs, directly acclimated from wastewater) gradually decayed by 50% from 1.2 ± 0.6 to 0.6 ± 0.6 A/m 2 ( n = 20, Figure C).…”