State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China.
State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai, China.
Sci Total Environ. 2022 Dec 10;851(Pt 1):158190. doi: 10.1016/j.scitotenv.2022.158190. Epub 2022 Aug 20.
In the rhizosphere, plant root exudates (REs) serve as a bridge between plant and soil functional microorganisms, which play a key role in the redox cycle of iron (Fe). This study examined the effects of periodic flooding and cadmium (Cd) on plant REs, the rhizosphere bacterial community structure, and the formation of root Fe plaques in the typical mangrove plant Kandelia obovata, as well as the relationship between REs and Fe redox cycling bacteria. Based on two-way analysis of variance, flooding and Cd had a considerable effect on the REs of K. obovata. DOC, NH-N, NO-N, dissolved inorganic phosphorus, acetic acid, and malonic acid concentrations in REs of K. obovata increased considerably with the increase of Cd concentration under 5 and 10 h flooding conditions. Fe plaque development in the plant root was stimulated by flooding and Cd, although flooding was more effective. After Cd treatment, the ways in which Fe-oxidizing bacteria (FeOB) and Fe-reducing bacteria (FeRB) were enriched in the rhizosphere and rhizoplane of plants were different. Thiobacillus and Sideroxydans (dominant FeOB) were more abundant in the plant rhizosphere, whereas Acinetobacter (dominant FeRB) was more abundant in the rhizoplane. Cd considerably decreased the relative abundance of unclassified_f_Gallionellaceae in the rhizosphere and rhizoplane but dramatically enhanced the relative abundance of Thiobacillus, Shewanella, and unclassified_f_Geobacteraceae. Unclassified_f_Geobacteraceae and Thiobacillus exhibited substantial positive correlations with citric acid and DOC in REs in the rhizosphere and rhizoplane but strong negative correlations with Sideroxydans. The findings indicate that Cd and flooding treatments may play a role in the production and breakdown of Fe plaque in K. obovata roots by affecting the relative abundance of Fe redox cycling bacteria in the rhizosphere and rhizoplane.
在根际中，植物根系分泌物（REs）作为植物和土壤功能微生物之间的桥梁，在铁（Fe）的氧化还原循环中起着关键作用。本研究考察了周期性淹水和镉（Cd）对典型红树林植物秋茄（Kandelia obovata）根际细菌群落结构和根铁斑块形成的影响，以及 REs 与 Fe 氧化还原循环细菌之间的关系。基于双向方差分析，淹水和 Cd 对秋茄根际 REs 有很大的影响。在 5 和 10 小时淹水条件下，随着 Cd 浓度的增加，REs 中 DOC、NH-N、NO-N、溶解无机磷、乙酸和丙二酸的浓度显著增加。淹水和 Cd 刺激了植物根中铁斑块的发育，尽管淹水的效果更为显著。Cd 处理后，Fe 氧化细菌（FeOB）和 Fe 还原细菌（FeRB）在植物根际和根面的富集方式不同。在植物根际中，硫杆菌属和纤发菌属（优势 FeOB）更为丰富，而不动杆菌属（优势 FeRB）在根面更为丰富。Cd 显著降低了根际和根面未分类的 f_浮霉菌科的相对丰度，但显著增加了硫杆菌属、希瓦氏菌属和未分类的 f_地杆菌科的相对丰度。未分类的 f_地杆菌科和硫杆菌属与根际和根面 REs 中的柠檬酸和 DOC 呈显著正相关，与纤发菌属呈强负相关。研究结果表明，Cd 和淹水处理可能通过影响根际和根面 Fe 氧化还原循环细菌的相对丰度，在秋茄根中铁斑块的产生和分解中发挥作用。
