This week Linden talks about methane as a greenhouse gas, and a new study showing that rivers with more waterfalls release more methane; and Stu runs us through the different parts of our immune system, including a recently discovered power of proteasomes within cells helping to attack invading bacteria. Rust, R.L., Frizzell, A. & Kessler, J.D. Waterfalls enhance regional methane emissions by enabling dissolved methane to bypass microbial oxidation. Commun Earth Environ 6, 140 (2025). https://doi.org/10.1038/s43247-025-02060-3 Goldberg, K., Lobov, A., Antonello, P. et al. Cell-autonomous innate immunity by proteasome-derived defence peptides. Nature (2025). https://doi.org/10.1038/s41586-025-08615-w