Microbes that Grab Power from Rocks: A New Gene Found in a Sea Bacterium

A marine bacterium, Thioclava electrotropha, can use solid surfaces as an energy source—a process called extracellular electron uptake (EEU). Scientists investigated how this organism achieves EEU by comparing gene expression when the bacteria grow on a metal surface versus when they oxidize sulfur.

Key Findings

• 584 genes were specifically active during EEU, many encoding c‑type cytochromes that reside between the cell membrane and outer shell.
• The gene pmcA stood out, being over a hundred times more active when the bacteria harvested electrons from a cathode.
• Deleting pmcA sharply reduced electron uptake; reintroducing it not only restored but enhanced the bacteria’s ability to capture electrons.

Gene Cluster and Evolution

• pmcA is part of a four‑gene cluster that likely collaborates in electron transfer.
• The cluster’s unusual DNA composition and its presence in over 2,500 other bacteria suggest acquisition via horizontal gene transfer.

Implications

These discoveries unveil a previously unknown mechanism by which bacteria harvest energy from solid materials. Understanding this pathway could aid in designing advanced bioelectrochemical devices that use living cells to generate power or remediate pollutants.