Some Bacteria Build Internal 'Power Cables' to Extend Respiration Beyond the Cell Membrane

All living cells generate energy mainly through respiration, a set of chemical reactions normally confined to the cell membrane. Because this machinery takes up space, a cell's energy-producing capacity has long been thought to depend on how much membrane it can build. Complex cells solve this with mitochondria packed with folded membranes, while some bacteria enlarge or reshape their own membranes to fit more of the machinery in.

A study published in Nature Microbiology describes a different solution. Researchers found that some bacteria build long, hollow filaments made of proteins and lipids that extend their respiratory machinery away from the membrane and into the interior of the cell. Electron-carrying molecules can move through the hollow core of these filaments, effectively forming power cables inside the cell.

This lets many energy-processing enzymes work beyond the cell membrane, expanding a bacterium's respiratory capacity without it having to build additional membrane or reorganize its structure. The discovery challenges the long-held view that respiration must remain confined to a membrane surface, showing instead that bacteria can construct what researchers describe as a microscopic power grid of protein-based extension cables carrying part of the respiratory chain into the cell's interior.

Related filament systems occur across hundreds of bacterial species, according to the researchers, suggesting the strategy is not a one-off but a widespread evolutionary solution. The study, led by researchers including Ashleigh Kropp, examined the bacterium Bacillus subtilis and related Gram-positive species, showing the filaments are made of quinone-transporting proteins that carry electrons as part of the respiratory chain.