Unveiling the Electric Marvels: How Bacteria Uncover Hidden Powers of Electricity Transfer
Editor's Note: As we continue to explore the intricate workings of life on Earth, we find that modes of operation once thought to be rare or confined to specific niches are now emerging in unexpected places. These capabilities are recurring and independent in various life forms, suggesting that what seems strange or alien to us might be commonplace elsewhere on our planet. Understanding this and other variants of 'traditional' biology is crucial for modeling, predicting, and searching for life beyond Earth, as well as comprehending its fundamental mechanisms.
For decades, scientists believed that only a select few bacteria utilized specialized molecular 'circuits' to shuttle electrons outside their cells, a process known as extracellular electron transfer (EET). This mechanism is vital for cycling carbon, sulfur, nitrogen, and metals in nature, and it underpins numerous applications, from wastewater treatment to bioenergy and bioelectronics materials. However, recent research from KAUST has revealed that this remarkable ability is far more versatile and widespread than previously thought.
The team, working with Desulfuromonas acetexigens, a bacterium capable of generating high electrical currents, combined bioelectrochemistry, genomics, transcriptomics, and proteomics to map its electron transfer machinery. To their surprise, they discovered that D. acetexigens simultaneously activated three distinct electron transfer pathways that were previously believed to have evolved separately in unrelated microbes: the metal-reducing (Mtr), outer-membrane cytochrome (Omc), and porin-cytochrome (Pcc) systems.
"This is the first time we've seen a single organism express these phylogenetically distant pathways in parallel," says first author Dario Rangel Shaw. "It challenges the long-held view that these systems were exclusive to specific microbial groups."
The team also identified unusually large cytochromes, including one with a record-breaking 86 heme-binding motifs, which could enable exceptional electron transfer and storage capacity. Tests showed that the bacterium could channel electrons directly to electrodes and natural iron minerals, achieving current densities comparable to the model species Geobacter sulfurreducens.
By extending their analysis to publicly available genomes, the researchers identified more than 40 Desulfobacterota species carrying similar multipathway systems across diverse environments, from sediments and soils to wastewater and hydrothermal vents. This reveals an unrecognized versatility in microbial respiration, as microbes with multiple electron transfer routes may gain a competitive advantage by tapping into a wider range of electron acceptors in nature.
The implications of this discovery extend far beyond ecology. Harnessing bacteria that can employ multiple electron transfer strategies could accelerate innovations in bioremediation, wastewater treatment, bioenergy production, and bioelectronics. For instance, electroactive biofilms like those formed by D. acetexigens could help recover energy from waste streams while simultaneously treating pollutants.
"Our findings expand the known diversity of electron transfer proteins and highlight untapped microbial resources," adds Pascal Saikaly, who led the study. "This opens the door to designing more efficient microbial systems for sustainable biotechnologies."
As researchers delve deeper into the microbial world, the discovery that a single bacterium can use multiple pathways underscores how much remains to be explored and how these hidden strategies could power a cleaner, more sustainable future. What other secrets might bacteria hold? And how can we harness these secrets to create a greener, more sustainable world? The answers may lie in the hidden powers of electricity transfer.
