Hidden bacterial hairs power nature’s ‘electric grid’

[william.scherk]

The topic headline is from material released from Yale. It concerns a study just published in Nature. From a Science Daily report:

A hair-like protein hidden inside bacteria serves as a sort of on-off switch for nature's 'electric grid,' a global web of bacteria-generated nanowires that permeates all oxygen-less soil and deep ocean beds, researchers report. 'The ground beneath our feet, the entire globe, is electrically wired,' said the senior author of the new article.

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Almost all living things breathe oxygen to get rid of excess electrons when converting nutrients into energy. Without access to oxygen, however, soil bacteria living deep under oceans or buried underground over billions of years have developed a way to respire by "breathing minerals," like snorkeling, through tiny protein filaments called nanowires.

Two proteins within buried bacteria, lacking oxygen, pump out nanowires, which essentially "exhale" electrons. Scientists are seeking to use this natural electrical grid to generate electricity, new biofuels and even self-healing electronic components.

Just how these soil bacteria use nanowires to exhale electricity, however, has remained a mystery. Since 2005, scientists had thought that the nanowires are made up of a protein called "pili" ("hair" in Latin) that many bacteria show on their surface. However, in research published 2019 and 2020, a team led by Malvankar showed that nanowires are made of entirely different proteins. "This was a surprise to everyone in the field, calling into question thousands of publications about pili," Malvankar said.

For the new study, graduate students Yangqi Gu and Vishok Srikanth used cryo-electron microscopy to reveal that this pili structure is made up of two proteins And instead of serving as nanowires themselves, pili remain hidden inside the bacteria and act like pistons, thrusting the nanowires into the environment. Previously nobody had suspected such a structure.

A video imaging the mechanics from Yale: