Microbial degradation and debromination have been demonstrated as effective strategies for mitigating the risks of BDE‑47, and several degrading strains have been isolated from coastal or terrestrial environments, with their transformation pathways preliminarily characterized. However, studies on the microbial degradation of BDE‑47 in deep‑sea extreme environments remain scarce, and the associated microbial resources and adaptation mechanisms are still poorly understood. In this study, a novel strain, Alteromonas abrolhosensis, was isolated from deep‑sea sediments and its ability to degrade BDE‑47 has been examined. By integrating concentration‑gradient acclimation culturing, toxicological assessment, degradation product analysis, and transcriptomic analysis, we systematically investigated both the major microbial groups responsible for BDE‑47 degradation in deep‑sea sediments and the biodegradation and adaptation mechanisms of A. abrolhosensis to BDE‑47. The 16S rRNA gene diversity analysis revealed that the microbial community structure underwent significant shifts during acclimation, with Alteromonas identified as the dominant degrading group. Degradation product analysis indicated that BDE‑47 underwent debromination, hydroxylation, ether bond cleavage, and ring‑opening, mediated by various intracellular oxidoreductases. Transcriptomic data further showed that the microorganisms alleviated BDE‑47‑induced oxidative stress through activation of the antioxidant defense system and biofilm formation. In addition, the enhanced synthesis of transporters and polyunsaturated fatty acids may facilitate the transport of BDE‑47 and the efflux of its degradation products, thereby increasing both the strain's tolerance to and degradation of BDE‑47. Overall, our findings provide novel insights into the degradation and adaptation mechanisms of deep‑sea microorganisms in response to BDE‑47, highlighting their considerable potential for bioremediation applications.