The gene encoding ornithine decarboxylase for putrescine biosynthesis is essential for the viability of <i>Fusobacterium nucleatum</i>

<i>Fusobacterium nucleatum</i> is a prominent member of the oral microbiota and has been linked to various human diseases, including periodontitis, preterm birth, and colorectal cancer. Despite its clinical significance, the metabolic requirements that support its growth and viability remain poorly understood. In this study, we identify the <i>oda</i> gene, which encodes ornithine decarboxylase, as essential for <i>F. nucleatum</i> survival due to its role in putrescine biosynthesis. We demonstrate that depletion of putrescine leads to severe growth and morphological defects, accompanied by widespread transcriptional changes. These findings reveal an underappreciated metabolic vulnerability and highlight the critical role of polyamine homeostasis in maintaining cellular integrity in this notorious anaerobe.