The conserved nature of nitrogen recycling within the bacterial pouch of Tetraponera ants

Microbial symbioses are fundamental to the nutrition of many animal groups, yet the mechanisms of nutrient recycling have only been characterized in a few social insect systems. Here, we investigate the functional significance of a specialized and unusual symbiotic organ—the bacterial pouch—in four ant species within the Tetraponera nigra -group, focusing on the symbionts’ roles in nitrogen recycling and colony fitness. This unique organ houses a microbial community consistently dominated by the co-diversifying bacterial symbiont Tokpelaia , occasionally accompanied by other stable bacterial associates. Metagenomic sequencing and targeted ¹⁵N-labeled urea feeding experiments demonstrate that these symbionts assimilate nitrogen from urea (likely derived from uric acid) and transfer it to adult workers and developing larvae, incorporating recycled nitrogen into host tissues. Disruption of this symbiosis severely impairs larval growth and overall colony fitness. Overall, our study highlights the critical role of the bacterial pouch in sustaining colony fitness in nitrogen-limited environments, providing new insights into the co-evolutionary dynamics between insect hosts and their microbial partners.