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ST Huber, D Terwiel, WH Evers, D Maresca, AJ Jakobi. Preprint 2022 doi: 10.1101/2022.05.08.489936
Many kinds of bacteria and archaea control their buoyancy to move to optimal positions in liquid environments. They do this by making nano-compartments called "gas vesicles", long "pipes" with closed ends filled with gases. In 2022, gas vesicle structure was solved, revealing self-assembling thin-walled cylinders of remarkable strength with gas-permeable pores and water-repelling (hydrophobic) interiors. Building on this structural knowledge, gas vesicles are being engineered to serve as biosensors that report via ultrasound.

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Y Gu, V Srikanth, AI Salazar-Morales, R Jain, JP O'Brien, SM Yi, RK Soni, FA Samatey, SE Yalcin, NS Malvankar. Nature 2021 doi: 10.1038/s41586-021-03857-w
Geobacter pili were long thought to be electrically conductive protein nanowires composed of PilA-N. Nanowires are crucial to the energy metabolism of bacteria flourishing in oxygen-deprived environments. To everyone's surprise, in 2019, the long-studied nanowires were found to be linear polymers of multi-heme cytochromes, not pili. The first cryo-EM structure of pili (2021) reveals a filament made of dimers of PilA-N and PilA-C, shown. Electrical conductivity of pili is much lower than that of cytochrome nanowires. Evidence suggests that PilA-NC filaments are periplasmic pseudopili crucial for exporting cytochrome nanowires onto the cell surface, rather than the pili serving as nanowires themselves.

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The Capsid of a virus is its outer shell or "skin". Viruses have evolved intricate and elegant ways to assemble capsid protein chains into complete, usually spherical capsids, often with icosahedral symmetry. Pictured is an extremely simplified model of a capsid, where a single enlarged atom represents each of the 360 protein chains in the capsid of the Simian Virus 40 (SV40), a member of a group of cancer-causing viruses that has been extensively researched for decades.

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