Biotransformation of 2-Aminobenzothiazole by a newly isolated Rhodococcus sp. YQ-4 eliminates its toxicity to sensitive organisms

An efficient Rhodococcus sp. YQ-4 strain degraded 98% of 2-ABT within 24 h. • A new intermediate metabolite (2-hydroxybenzothiazole) was identified. • A novel 2-ABT biotransformation pathway was proposed. • Biodegradation of 2-ABT was a detoxification process. 2-Aminobenzothiazole (2-ABT), a representative heterocyclic compound originating from tire wear particles, was widely detected in diverse environmental matrices. Due to its persistence and potential toxicity, the removal of 2-ABT from contaminated environments has become an increasing environmental concern. However, studies on the efficient biodegradation of 2-ABT by pure cultures remain limited. In this study, the abundance of Rhodococcus increased significantly following enrichment and acclimation. Subsequently, a 2-ABT-degrading pure culture, designated Rhodococcus sp. YQ-4, was isolated. Under the optimal conditions of pH 7.0, 1% NaCl, and 30 °C, strain YQ-4 achieved a removal rate of 98% for 50 μM 2-ABT within 24 h. A key metabolic intermediate, 2-hydroxybenzothiazole (2-OBT), was identified by liquid chromatography-time-of-flight mass spectrometry (LC-TOF-MS). Based on these results, a possible initial biotransformation pathway involving deamination and hydroxylation at the C2 position of the thiazole ring was proposed. Furthermore, toxicity bioassays involving the green alga Chlamydomonas ellipsoidea and mung bean ( Vigna radiata ) demonstrated that the biodegradation of 2-ABT by strain YQ-4 significantly alleviated its phytotoxicity, thereby restoring the growth and physiological vigor of the test species. Collectively, this study provided a novel bacterial resource for the bioremediation of 2-ABT-contaminated environments and offered new insights into the catabolic pathway associated with emerging pollutants.