Jackson C A, Couger M B, Prabhakaran M, Ramachandriya K D, Canaan P, Fathepure B Z
Department of Microbiology and Molecular Genetics, Oklahoma State University, Stillwater, OK, USA.
Department of Biosystems and Agricultural Engineering, Oklahoma State University, Stillwater, OK, USA.
J Appl Microbiol. 2017 Apr;122(4):940-952. doi: 10.1111/jam.13401. Epub 2017 Feb 27.
The aim of this work was to isolate novel lignin-degrading organisms.
Several pure cultures of bacteria that degrade lignin were isolated from bacterial consortia developed from decaying biomass. Among the isolates, Rhizobium sp. strain YS-1r (closest relative of Rhizobium petrolearium strain SL-1) was explored for its lignin-degrading ability. Microcosm studies showed that strain YS-1r was able to degrade a variety of lignin monomers, dimers and also native lignin in switchgrass and alfalfa. The isolate demonstrated lignin peroxidase (LiP) activity when grown on alkali lignin, p-anisoin, switchgrass or alfalfa, and only negligible activity was measured in glucose-grown cells suggesting inducible nature of the LiP activity. Analysis of the strain YS-1r genome revealed the presence of a variety of genes that code for various lignin-oxidizing, H O -producing as well as polysaccharide-hydrolysing enzymes.
This study shows both the genomic and physiological capability of bacteria in the genus Rhizobium to metabolize lignin and lignin-like compounds. This is the first detailed report on the lignocellulose-degrading ability of a Rhizobium species and thus this study expands the role of alpha-proteobacteria in the degradation of lignin.
The organism's ability to degrade lignin is significant since Rhizobia are widespread in soil, water and plant rhizospheres and some fix atmospheric nitrogen and also have the ability to degrade aromatic hydrocarbons.
本研究旨在分离新型木质素降解微生物。
从腐烂生物质培养的细菌群落中分离出几种降解木质素的纯培养细菌。在这些分离菌株中，研究了根瘤菌属的YS-1r菌株（与石油根瘤菌SL-1菌株亲缘关系最近）的木质素降解能力。微观世界研究表明，YS-1r菌株能够降解多种木质素单体、二聚体以及柳枝稷和苜蓿中的天然木质素。该分离菌株在以碱性木质素、对甲氧基苯乙酮、柳枝稷或苜蓿为生长底物时表现出木质素过氧化物酶（LiP）活性，而在以葡萄糖为生长底物的细胞中仅检测到可忽略不计的活性，这表明LiP活性具有诱导性。对YS-1r菌株基因组的分析揭示了存在多种编码各种木质素氧化、产H₂O₂以及多糖水解酶的基因。
本研究表明根瘤菌属细菌在代谢木质素和类木质素化合物方面具有基因组和生理能力。这是关于根瘤菌属物种木质纤维素降解能力的首份详细报告，因此本研究扩展了α-变形菌在木质素降解中的作用。
该生物体降解木质素的能力具有重要意义，因为根瘤菌广泛存在于土壤、水和植物根际，一些根瘤菌能够固定大气中的氮，并且还具有降解芳香烃的能力。
