ALT https://www.pnas.org/doi/10.1073/pnas.2306160120 Pictured is a transmission electron micrograph of a section near the tip of a Ca. Epulopiscium viviparus cell, showing a complex internal membrane system. David R. Sannino et al. generated a high-quality draft genome of the giant bacterium, which survives as a symbiont in the intestines of unicornfish. More than 5% of the bacterial genome encodes enzymes that may degrade polysaccharides in the host diet from which the bacterium derives energy. Gene transcription analysis suggested that the bacterium also uses sodium from the host’s intestinal tract to drive energy synthesis and flagellar rotation. According to the authors, the study suggests that the giant bacterium uses the host environment to meet its high energy needs. See the article by Sannino et al. e2306160120. Image credit: Nathalie H. Elisabeth.