Deng Jun-Jin, Deng Dun, Wang Zhi-Lin, Luo Xiao-Chun, Chen Hong-Ping, Liu Shu-Yang, Ma Xian-Yong, Li Jia-Zhou
Institute of Animal Science, Guangdong Academy of Agricultural Sciences, State Key Laboratory of Livestock and Poultry Breeding, The Key Laboratory of Animal Nutrition and Feed Science in South China, Ministry of Agriculture and Rural Affairs, Guangdong Key Laboratory of Animal Breeding and Nutrition, No. 1 Dafeng Street, Wushan Road, Tianhe District, Guangzhou, Guangdong 510640, China.
Agro-Biological Gene Research Center, Guangdong Academy of Agricultural Sciences, Guangzhou 510640, China.
J Hazard Mater. 2022 Jul 15;434:128890. doi: 10.1016/j.jhazmat.2022.128890. Epub 2022 Apr 12.
Indole is an inter-species and inter-kingdom signaling molecule widespread in the natural world. A large amount of indole in livestock wastes makes it difficult to be degraded, which causes serious malodor. Identifying efficient and eco-friendly ways to eliminate it is an urgent task for the sustainable development of husbandry. While bioconversion is a widely accepted means, the mechanism of indole microbial degradation is little understood, especially under anaerobic conditions. Herein, a new Enterococcus hirae isolate GDIAS-5, effectively degraded 100 mg/L indole within 28 h aerobically or 5 days anaerobically. Three intermediates (oxindole, isatin, and catechol) were identified in indole degradation, and catechol was further degraded by a meta-cleavage catabolic pathway. Two important processes for GDIAS-5 indole utilization were discovered. One is Fe(III) uptake and reduction, which may be a critical process that is coupled with indole oxidation, and the other is the entire pathway directly involved in indole oxidation and metabolism. Furthermore, monooxygenase ycnE responsible for indole oxidation via the indole-oxindole-isatin pathway was identified for the first time. Bioinformatic analyses showed that ycnE from E. hirae formed a phylogenetically separate branch from monooxygenases of other species. These findings provide new targets and strategies for synthetic biological reconstruction of indole-degrading bacteria.
吲哚是一种在自然界广泛存在的种间和跨界信号分子。畜禽粪便中大量的吲哚难以降解，会产生严重的恶臭。寻找高效且环保的吲哚去除方法是畜牧业可持续发展的紧迫任务。虽然生物转化是一种被广泛接受的手段，但吲哚微生物降解的机制尚不清楚，尤其是在厌氧条件下。在此，新分离出的平肠球菌GDIAS-5在有氧条件下28小时内或厌氧条件下5天内可有效降解100mg/L的吲哚。在吲哚降解过程中鉴定出三种中间产物（氧化吲哚、异吲哚酮和邻苯二酚），邻苯二酚通过间位裂解分解代谢途径进一步降解。发现了GDIAS-5利用吲哚的两个重要过程。一个是铁（III）的摄取和还原，这可能是与吲哚氧化偶联的关键过程，另一个是直接参与吲哚氧化和代谢的完整途径。此外，首次鉴定出通过吲哚-氧化吲哚-异吲哚酮途径负责吲哚氧化的单加氧酶ycnE。生物信息学分析表明，平肠球菌的ycnE与其他物种的单加氧酶在系统发育上形成了一个独立的分支。这些发现为吲哚降解菌的合成生物学改造提供了新的靶点和策略。
