Transformation of arsenic species by diverse endophytic bacteria of rice roots.
Transformation of arsenic species by diverse endophytic bacteria of rice roots.
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DOI：
10.1016/j.envpol.2022.119825
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发表时间：
2022-07
影响因子：
8.9
通讯作者：
Chuan Chen;Baoyun Yang;Axiang Gao;Yu Yu-Yu;F. Zhao
中科院分区：
文献类型：
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作者：
Chuan Chen;Baoyun Yang;Axiang Gao;Yu Yu-Yu;F. Zhao
在淹水水稻土中生长的水稻往往积累了相当多的无机和有机砷，这可能对植物造成毒性和/或对人类健康构成风险。土壤中砷的生物利用度和毒性取决于其化学物质，这些化学物质主要由土壤微生物驱动，经历多次转化。然而，水稻根系内生菌在水稻As物种转化中的作用仍不清楚。通过盆栽试验，定量分析了3种水稻土中水稻根系内圈和根际中参与砷转化的微生物功能基因的丰度。我们还分离了46种不同的细菌内生菌，并测试了它们转化各种As的能力。砷酸盐还原酶基因和异化砷酸盐还原酶基因在根际的绝对丰度与根际相当，而亚砷酸盐甲基化基因和亚砷酸盐氧化基因在根际的绝对丰度较低。基于细菌16S rRNA基因归一化后，4种As转化基因在内球圈的相对丰度均高于根际。与功能基因数据一致，30株好氧内生菌均能还原砷酸盐，但只有3株能氧化亚砷酸盐。在16株厌氧内生菌株中，有4株属于Desulfovibrio、terrisporobacterium和Clostridium，可以甲基化亚砷酸盐和/或甲基亚砷酸盐。6株需氧内生菌能对甲基larsenite进行去甲基化，其中3株也能对甲基larsenate进行还原和去甲基化。所有分离株均不能使二甲基larate去甲基化。这些结果表明，生活在水稻根系内的多种内生菌参与了砷的转化，影响了砷在水稻植株内的积累和分布。
Rice growing in flooded paddy soil often accumulates considerable levels of inorganic and organic arsenic (As) species, which may cause toxicity to plants and/or pose a risk to human health. The bioavailability and toxicity of As in soil depends on its chemical species, which undergo multiple transformations driven primarily by soil microbes. However, the role of endophytes inside rice roots in As species transformation remains largely unknown. We quantified the abundances of microbial functional genes involved in As transformation in the endosphere and rhizosphere of rice roots growing in three paddy soils in a pot experiment. We also isolated 46 different bacterial endophytes and tested their abilities to transform various As species. The absolute abundances of the arsenate reductase genearsCand the dissimilatory arsenate reductase genearrAin the endosphere were comparable to those in the rhizosphere, whereas the absolute abundances of the arsenite methylation genearsMand arsenite oxidation geneaioAin the endosphere were lower. After normalization based on the bacterial 16S rRNA gene, all four As transformation genes showed higher relative abundances in the endosphere than in the rhizosphere. Consistent with the functional gene data, all of the 30 aerobic endophytic isolates were able to reduce arsenate, but only 3 strains could oxidize arsenite. Among the 16 anaerobic endophytic isolates, 4 strains belonging to Desulfovibrio,Terrisporobacteror Clostridium could methylate arsenite and/or methylarsenite. Six strains of aerobic endophytes could demethylate methylarsenite, among which three strains also could reduce and demethylate methylarsenate. None of the isolates could demethylate dimethylarsenate. These results suggest that diverse endophytes living inside rice roots could participate in As species transformation and affect As accumulation and species distribution in rice plants.