Naphthenic acids (NAs) are a persistent toxic organic pollutant that occur in different environment worldwide and cause serious threat to the ecosystem and public health. However, knowledge on the behavior and fate of NAs in marine environments still remains unknown. In this study, the degradation mechanism of NAs (cyclohexylacetic acid, CHAA) was investigated using an common indigenous marine Pseudoalteromonas sp. The results showed that CHAA could be degraded completely under aerobic condition, but could not be utilized directly under anaerobic condition. Interestingly, transcriptome and key enzyme activity results showed the CHAA degradation pathway induced under aerobic condition could still work in anaerobic condition. The degradation was activated by acetyl-CoA transferase and sequentially formed the corresponding cyclohexene, alcohol, and ketone with the assistance of related enzymes, and finally cleaved by hydroxymethylglutarate-CoA lyase. Besides, there was a positive correlation between chemotaxis and aerobic degradation genes (r=0.976, P<0.05), the chemotaxis would enhance bacterium movement and NAs biodegradation. It is proposed that bacterium could translocate to NAs and accomplish biodegradation from aerobic to anaerobic environments, which was a new anaerobic degradation pathway of NAs. This study provides new insights into the fate of NAs and other organic contaminants in marine environment.

环烷酸（NAs）是一种持久性有毒有机污染物，存在于全球不同环境中，对生态系统和公众健康造成严重威胁。然而，关于 NA 在海洋环境中的行为和命运的知识仍然未知。在这项研究中，使用常见的本土海洋假单胞菌研究了NAs（环己基乙酸，CHAA）的降解机制。sp。结果表明，CHAA在好氧条件下可以完全降解，但在厌氧条件下不能直接利用。有趣的是，转录组和关键酶活性结果表明，在好氧条件下诱导的 CHAA 降解途径在厌氧条件下仍然有效。降解由乙酰辅酶A转移酶激活，在相关酶的帮助下依次形成相应的环己烯、醇和酮，最后被羟甲基戊二酸辅酶A裂解酶裂解。此外，趋化性与好氧降解基因呈正相关（r=0.976，P<0.05)，趋化性将增强细菌运动和 NAs 生物降解。提出细菌可以转运至NAs并完成从好氧环境到厌氧环境的生物降解，这是NAs的一种新的厌氧降解途径。这项研究为海洋环境中 NA 和其他有机污染物的命运提供了新的见解。