Universidad Adolfo Ibáñez, Santiago, Chile.
Antonie Van Leeuwenhoek. 2012 May;101(4):713-23. doi: 10.1007/s10482-011-9685-8. Epub 2011 Dec 21.
Plant rhizosphere and internal tissues may constitute a relevant habitat for soil bacteria displaying high catabolic versatility towards xenobiotic aromatic compounds. Root exudates contain various molecules that are structurally related to aromatic xenobiotics and have been shown to stimulate bacterial degradation of aromatic pollutants in the rhizosphere. The ability to degrade specific aromatic components of root exudates could thus provide versatile catabolic bacteria with an advantage for rhizosphere colonization and growth. In this work, Cupriavidus pinatubonensis JMP134, a well-known aromatic compound degrader (including the herbicide 2,4-dichlorophenoxyacetate, 2,4-D), was shown to stably colonize Arabidopsis thaliana and Acacia caven plants both at the rhizoplane and endorhizosphere levels and to use root exudates as a sole carbon and energy source. No deleterious effects were detected on these colonized plants. When a toxic concentration of 2,4-D was applied to colonized A. caven, a marked resistance was induced in the plant, showing that strain JMP134 was both metabolically active and potentially beneficial to its host. The role for the β-ketoadipate aromatic degradation pathway during plant root colonization by C. pinatubonensis JMP134 was investigated by gene inactivation. A C. pinatubonensis mutant derivative strain displayed a reduced ability to catabolise root exudates isolated from either plant host. In this mutant strain, a lower competence in the rhizosphere of A. caven was also shown, both in gnotobiotic in vitro cultures and in plant/soil microcosms.
植物根际和内部组织可能构成一个相关的栖息地，其中含有具有高代谢多样性的土壤细菌，可以代谢芳香族污染物。根分泌物中含有各种与芳香族污染物结构相关的分子，已被证明能刺激根际中芳香族污染物的细菌降解。因此，能够降解根分泌物中特定芳香族成分的能力可能为具有多功能代谢能力的细菌在根际定殖和生长提供优势。在这项工作中，已经证明 Cupriavidus pinatubonensis JMP134 是一种熟知的芳香族化合物降解菌（包括除草剂 2,4-二氯苯氧乙酸，2,4-D），它可以稳定地定殖于拟南芥和金合欢植物的根际和根内区，并将根分泌物作为唯一的碳源和能源。在这些定殖植物上没有检测到有害影响。当向定殖的金合欢植物施用有毒浓度的 2,4-D 时，植物会产生明显的抗性，表明 JMP134 菌株不仅具有代谢活性，而且对其宿主可能有益。通过基因失活研究了 C. pinatubonensis JMP134 定殖植物根际过程中β-酮戊二酸芳香族降解途径的作用。C. pinatubonensis 的突变衍生菌株显示出代谢根分泌物的能力降低，这些分泌物来自于两种植物宿主。在这个突变菌株中，还显示出在金合欢的根际中竞争能力降低，无论是在无菌体外培养还是在植物/土壤微宇宙中。
