Exploring the Roles of Tuna‐Associated <i>Acinetobacter</i> sp. YFT067: Implications for Host Health and Metabolism

ABSTRACT The gut microbiome and its metabolites are vitally important for host dietary digestion, nutrient absorption, and energy metabolism. Yellowfin tuna ( Thunnus albacares ), a large warm‐blooded fish that sustains continuous high‐speed swimming, demonstrates higher energy demands than other fish. However, there are no relevant reports on the functional contribution of specialized gut microbiota to energy homeostasis of tuna. To bridge this knowledge gap, we characterized the function of a new bacterial strain, Acinetobacter seifertii YFT067, derived from the intestine of wild yellowfin tuna. According to whole genome sequencing, YFT067 exhibited the probiotic potential with a high ability in nutrient metabolism. In vitro test demonstrated that YFT067 is tolerant to the simulated gastroenteric juice and strong in adhesion. The six‐week zebrafish feeding trial with 10 8 CFU/g YFT067 strain supplementation significantly enhanced body growth, feed conversion, and digestive enzyme activity of the host as well as the intestinal health, including enhanced goblet cells number and short‐chain fatty acids (propionate, butyrate, and valerate) contents. Transcriptomic analysis revealed that the digestive system and metabolism process were significantly up‐regulated with fabp , fatp4 , mgat3a , acat1 , apoa1b , and apoa4a enriched in the fat digestive and absorption pathway and pltp , cetp , and nceh1a enriched in the cholesterol metabolism pathway. These findings indicated A . seifertii YFT067 as a promising probiotic candidate for enhancing tuna farming production through improving metabolic efficiency and intestinal health. Our study provides foundational evidence for developing YFT067‐based probiotic formulations to optimize growth performance and cultivation sustainability in tuna aquaculture.