Parthasarathy Anutthaman, Miranda Renata Rezende, Eddingsaas Nathan C, Chu Jonathan, Freezman Ian M, Tyler Anna C, Hudson André O
Thomas H. Gosnell School of Life Sciences, Rochester Institute of Technology, Rochester, NY 14623, USA.
School of Chemistry and Biosciences, University of Bradford, Bradford BD7 1DP, UK.
Microorganisms. 2022 Aug 10;10(8):1619. doi: 10.3390/microorganisms10081619.
The widespread use of plastics has led to their increasing presence in the environment and subsequent pollution. Some microorganisms degrade plastics in natural ecosystems and the associated metabolic pathways can be studied to understand the degradation mechanisms. Polystyrene (PS) is one of the more recalcitrant plastic polymers that is degraded by only a few bacteria. is a genus of Gram-positive poly-extremophilic bacteria known to degrade PS, thus being of biotechnological interest, but its biochemical mechanisms of degradation have not yet been elucidated. Based solely on genome annotation, we initially proposed PS degradation by sp. RIT 594 via depolymerization and epoxidation catalyzed by a ring epoxidase. However, Fourier transform infrared (FTIR) spectroscopy analysis revealed an increase of carboxyl and hydroxyl groups with biodegradation, as well as of unconjugated C-C double bonds, both consistent with dearomatization of the styrene ring. This excludes any aerobic pathways involving side chain epoxidation and/or hydroxylation. Subsequent experiments confirmed that molecular oxygen is critical to PS degradation by RIT 594 because degradation ceased under oxygen-deprived conditions. Our studies suggest that styrene breakdown by this bacterium occurs via the sequential action of two enzymes encoded in the genome: an orphan aromatic ring-cleaving dioxygenase and a hydrolase.
塑料的广泛使用导致其在环境中的存在日益增加并造成后续污染。一些微生物在自然生态系统中降解塑料，相关的代谢途径可用于研究降解机制。聚苯乙烯（PS）是较难降解的塑料聚合物之一，只有少数细菌能够降解它。 是一类革兰氏阳性多极端嗜性细菌，已知能够降解PS，因此具有生物技术研究价值，但其生化降解机制尚未阐明。仅基于基因组注释，我们最初提出 菌属RIT 594通过环氧化酶催化的解聚和环氧化作用降解PS。然而，傅里叶变换红外（FTIR）光谱分析表明，随着生物降解，羧基和羟基以及未共轭的C-C双键增加，这两者都与苯乙烯环的脱芳构化一致。这排除了任何涉及侧链环氧化和/或羟基化的需氧途径。后续实验证实，分子氧对RIT 594降解PS至关重要，因为在缺氧条件下降解停止。我们的研究表明，这种细菌对苯乙烯的分解是通过基因组中编码的两种酶的顺序作用发生的：一种孤儿芳香环裂解双加氧酶和一种水解酶。
