Chemosphere：Burkholderia sp. Y4通过增加水稻必需营养元素摄取并优先吸收...

农业农村部环境保护科研监测所刘仲齐研究员团队的王常荣等从污染农田水稻根际土壤中分离纯化出一株耐镉促生菌，并分析了该菌株抑制水稻镉积累的作用机制。相关成果发表于Chemosphere（IF=5.108）。

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Highlights

·Burkholderia sp. Y4 inoculation reduced Cd accumulation in rice.

·Burkholderia sp. Y4 increased the content of Fe and Mn in rice rachises and grains.

·Burkholderia sp. Y4 colonized the surface of rice roots to preferentially absorb Cd.

·Y4 altered soil bacterial community to indirectly modulate iron and nitrogen cycling.

Abstract

Microbial remediation of heavy metal-polluted soil is a commonly used method. Burkholderia sp. Y4, isolated from cadmium (Cd)-contaminated rice rhizosphere soil, was investigated for its direct and indirect effects on Cd accumulation in rice by SEM-EDS, FITR and sequencing analysis of the soil bacterial community. Burkholderia sp. Y4 inoculation reduced Cd accumulation in rice roots, rachises, and grains of the two rice varieties T705 and X24 and increased levels of essential elements, especially Fe and Mn, which competitively inhibited Cd transport through cationic channels. Living Burkholderia sp. Y4 cells, rather than non-living ones, could colonize the surface of rice roots and accumulated more Cd through direct biosorption associated with –C=O and –NH/−C=O bonds of amino acids and proteins. The results of soil microbial community showed that the colonization of externally added Burkholderia sp. Y4 could be maintained over some time to impact the total rhizospheric environment. Burkholderia sp. Y4 inoculation decreased the abundance of microbes involved in the iron cycle (Acidobacteria) as well as of those mediating the transformation of ammonium nitrogen to nitrate nitrogen (Nitrosomonadaceae and Nitrospira). So Burkholderia sp. Y4 inoculation may indirectly change the availability of micronutrients and Cd in rice rhizosphere soil through iron-nitrogen coupled cycles to increase essential nutrient uptake and inhibit Cd accumulation in rice by preferential Cd-biosorption. Therefore, Burkholderia sp. Y4 is potentially suitable for the bioremediation of Cd-contaminated paddy soil.

微生物修复是重金属污染土壤治理的一种常用方法。本研究从污染农田水稻根际土壤中分离纯化出一株耐镉促生菌，经鉴定为伯克氏菌Burkholderia sp. Y4，并通过SEM-EDS、FITR和土壤细菌群落序列分析等方法，分析了菌株对水稻镉积累的直接作用和间接影响。结果表明，接种菌株Y4降低了不同品种（T705和X24）水稻根、穗轴和籽粒中镉的积累，同时提高了必需营养元素（特别是铁和锰）的含量，必需元素阳离子能够竞争性地抑制镉通过水稻细胞膜阳离子通道进行转运。此外，菌株活细胞还可以定殖在水稻根表，并通过与氨基酸和蛋白质的-C=O和-NH/-C=O等官能团结合直接优先吸附积累镉，而非活性菌株细胞则无法定殖于水稻根表。进一步研究土壤菌群结构发现，外源添加的菌株Y4在根际土壤中的定殖可以维持一段时间，从而影响水稻根际环境。接种菌株Y4降低了参与铁循环的酸杆菌属以及介导铵态氮向硝态氮转化的亚硝化单胞菌科和硝化螺菌属的相对丰度。因此，菌株Y4很可能通过调控铁氮耦合循环，间接地影响水稻根际土壤中微量营养元素和镉的可利用性，进而促进水稻必需元素的吸收，并通过菌株优先吸附镉的方式抑制水稻镉吸收积累。因此，Burkholderia sp. Y4可能适用于镉污染水稻田的生物修复。