Screening, identification, metabolic pathway of di-n-butyl phthalate degrading Priestia megaterium P-7 isolated from long-term film mulched cotton field soil in Xinjiang

Zhidong Zhang^1,2*Yuanyang Yi³Yuxian Wang⁴Wanqin Liu⁴Jing Zhu²Meiying Gu²Qiong Jia²Xue Li⁵Munire Mutalifu⁵Ling Jiang⁶Wei Zhang³

• ¹Institute of Microbiology, Xinjiang Academy of Agricultural Sciences, Urumuqi, China
• ²Xinjiang Academy of Agricultural Sciences, Urumqi, China
• ³Xinjiang Normal University, Urumqi, Xinjiang Uyghur Region, China
• ⁴Xinjiang University, Urumqi, Xinjiang Uyghur Region, China
• ⁵Xinjiang Agricultural University, Ürümqi, Xinjiang Uyghur Region, China
• ⁶Nanjing Tech University, Nanjing, Jiangsu Province, China

Di-n-butyl phthalate (DBP) is one of the most widely used phthalate esters (PAEs) and is considered an emerging global pollutant. It may pose a significant threat to ecosystem and human health due to its residual hazards and accumulation in the environment. Bacteria-driven PAE biodegradation is considered an economical and effective strategy for remediating such polluted environments. In this study, a DBP degrading bacterium, strain P-7, was isolated from long-term plastic film mulched cotton field soil. Based on its physiological and biochemical properties and 16S rRNA gene sequence homology analysis, the strain was identified as Priestia megaterium P-7 (P. megaterium P-7). By optimizing the degradation ability of P. megaterium P-7 under different environmental conditions, the strain could achieve 100% removal of DBP within 20 h under optimal conditions. In addition, the strain exhibited a broad substrate utilization profile, demonstrating excellent degradation of other PAEs.Furthermore, the whole-genome sequencing of strain revealed the molecular mechanism of PAE biodegradation. Genes (lip, aes, ybfF, estA, and yvaK) encoding key enzymes such as esterases/hydrolases facilitated the conversion of DBP to PA, which was then converted to catechol by decarboxylases (pdc, bsdCD, mdcACDH, and lysA) and dioxygenases, ultimately entering the TCA cycle. Additionally, metabolomics analysis further revealed three potential DBP degradation pathways: decarboxylation (DBP→MBP→BB→BA→Catechol), hydrolysis (DBP→MBP→PA→PCA→Catechol) and direct β-oxidation (DBP→DEP→MEP→PA→Catechol). Overall, P. megaterium P-7 demonstrated excellent degradation efficiency, substrate versatility, and environmental stress tolerance, making it a promising candidate for bioremediation of organic pollutants in contaminated soil.