Abstract:[Background] The ocean is the largest reservoir of carbon and the largest habitat for life on the Earth. This vast ecosystem harbors a wide variety of microorganisms that play a key role in the global carbon cycle. Hadal trench (6 000 m below the sea level) is a special habitat containing rich biological resources owing to the high hydrostatic pressure and the accumulation of massive organic matter by surface deposition. [Objective] To obtain the bacterial pure culture capable of utilizing aromatic acids as the sole carbon and energy from the hadal trench sediment samples, and analyze its aromatic acid-degrading characteristics. [Methods] The hadal trench sediment sample was cultivated in the simulated in situ high-pressure environment, and then the culture was incubated on the plates with different aromatic acids under atmospheric ambient pressure. Finally, the bacterial pure culture was selected and identified based on the morphological characteristics and the phylogenetic tree constructed with the 16S rRNA gene. The strain was then incubated with different aromatic acids, and the degradation intermediates were identified by HPLC and LC/MS. [Results] A strain capable of utilizing benzoate and 4-hydroxybenzoate was isolated from the sediment sample from Mariana trench (6 300 m below the sea level). It belonged to the genus Halomonas and was designated Halomonas sp. strain NyZ771. The intermediate in 4-hydroxybenzoate degradation was identified as protocatechuate. [Conclusion] A benzoate- and 4-hydroxybenzoate-degrading bacterium, Halomonas sp. strain NyZ771, was isolated from the trench sediment. This study enriches the microbial resources derived from the hadal trench and provides a theoretical foundation for the future research on the aromatic acid degradation in hadal trenches and the carbon cycle driven by microorganisms in the ocean.
