Quantitative proteomic analysis of the exoelectrogenic bacterium Arcobacter butzleri ED-1 reveals increased abundance of a flagellin protein under anaerobic growth on an insoluble electrode

Exoelectrogens have the ability to generate electricity in mediator-less microbial fuel cells (MFCs) by extracellular electron transfer to the anode. We investigate the anode-specific responses of Arcobacter butzleri ED-1, the first identified exoelectrogenic Epsilonproteobacterium. iTRAQ and 2D-LC MS/MS driven proteomics were used to compare protein abundances in A. butzleri ED-1 when generating an electronegative potential (− 225 mV) in an anaerobic half-cell — either growing as an electrogenic biofilm or suspended in the liquid medium - versus a microaerobic culture. This is the first quantitative proteomic study concentrating on growth of an exoelectrogen during current generation. From 720 proteins identified and quantified (soluble and insoluble sub-proteomes), statistical analysis reveals 75 differentially-expressed proteins. This dataset was enriched in proteins regulating energy and intermediary metabolism, electron and protein transport. Flagellin up-regulation was concomitant with electron transport in the anodic cells, while decreased abundance of a methyl-accepting chemotaxis protein suggested that flagella were involved in communication with the anode surface and electrogenesis, rather than motility. Two novel cytochromes potentially related to electron transport were up-regulated in anaerobic cultures. We demonstrate that employing an insoluble extracellular electron acceptor for anaerobic growth regulates multiple proteins involved in cell surface properties, electron transport and the methylcitrate cycle.

Figure optionsDownload high-quality image (68 K)Download as PowerPoint slideHighlights
► First iTRAQ-based study of protein expression in an exoelectrogen.
► Soluble and insoluble sub-proteomes when generating electronegative potential.
► Out of 720 proteins identified and quantified, 75 were differentially expressed.
► Differential expression of flagellin, cytochromes and methyl citrate cycle