Metabolites produced by Pseudomonas sp. enable a Gram-positive bacterium to achieve extracellular electron transfer.
Previous studies revealed the abundance of Pseudomonas sp. in the microbial community of a microbial fuel cell (MFC). These bacteria can transfer electrons to the electrode via self-produced phenazine-based mediators. A MFC fed with acetate where several Pseudomonas sp. were present was found to be rich in a Gram-positive bacterium, identified as Brevibacillus sp. PTH1. Remarkably, MFCs operated with only the Brevibacillus strain in their anodes had poor electricity generation. Upon replacement of the anodic aqueous part of Brevibacillus containing MFCs with the cell-free anodic supernatants of MFCs operated with Pseudomonas sp. CMR12a, a strain producing considerable amounts of phenazine-1-carboxamide (PCN) and biosurfactants, the electricity generation was improved significantly. Supernatants of Pseudomonas sp. CMR12a_Reg, a regulatory mutant lacking the ability to produce PCN, had no similar improvement effect. Purified PCN, together with rhamnolipids as biosurfactants (1 mg L(-1)), could clearly improve electricity generation by Brevibacillus sp. PTH1, as well as enable this bacterium to oxidize acetate with concomitant reduction of ferric iron, supplied as goethite (FeOOH). When added alone, PCN had no observable effects on Brevibacillus' electron transfer. This work demonstrates that metabolites produced by Pseudomonas sp. enable Gram-positive bacteria to achieve extracellular electron transfer. Possibly, this bacterial interaction is a key process in the anodic electron transfer of a MFC, enabling Brevibacillus sp. PTH1 to achieve its dominance.
Pham
The Hai
TH
Laboratory of Microbial Ecology and Technology (LabMET), Ghent University, Coupure Links 653, 9000, Ghent, Belgium.
Boon
Nico
N
Aelterman
Peter
P
Clauwaert
Peter
P
De Schamphelaire
Liesje
L
Vanhaecke
Lynn
L
De Maeyer
Katrien
K
Höfte
Monica
M
Verstraete
Willy
W
Rabaey
Korneel
K
D000085:Acetates; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004560:Electricity; D004566:Electrodes; D004579:Electron Transport; D006017:Glycolipids / Q000378:metabolism; D006094:Gram-Positive Bacteria / Q000378:metabolism*; D058085:Iron Compounds / Q000378:metabolism; D008903:Minerals; D008969:Molecular Sequence Data; D010084:Oxidation-Reduction; D010619:Phenazines / Q000378:metabolism; D011549:Pseudomonas / Q000378:metabolism*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D017422:Sequence Analysis, DNA; D013501:Surface-Active Agents / Q000378:metabolism
D000085:Acetates; D004269:DNA, Bacterial; D006017:Glycolipids; D058085:Iron Compounds; D008903:Minerals; D010619:Phenazines; D012336:RNA, Ribosomal, 16S; D013501:Surface-Active Agents; C420923:phenazine-1-carboxamide; C418382:rhamnolipid; C094886:goethite