Articles of Significant Interest in This Issue

Biological N2 fixation via nitrogenases is an ancient process that preferentially fixes 14N over 15N into ammonia. In this Planetary Microbiology Special Collection article (e00574-24), Wannicke et al. confirm the stability of this signal in primary producers under conditions mirroring those of a pre-Cambrian Earth and demonstrate increased fractionation in toxin-producing cyanobacteria. These findings offer a glimpse into N2 fixation activities under past, present, and future planetary scenarios.