Department of Microbiology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland; Interdisciplinary Centre of Modern Technologies, Nicolaus Copernicus University, Wileńska 4, 87-100 Toruń, Poland.
Department of Microbiology, Faculty of Biology and Environmental Protection, Nicolaus Copernicus University, Lwowska 1, 87-100 Torun, Poland.
Chemosphere. 2016 Aug;156:312-325. doi: 10.1016/j.chemosphere.2016.04.130. Epub 2016 May 13.
Rhizosphere and endophytic bacteria are well known producers of siderophores, organic compounds that chelate ferric iron (Fe(3+)), and therefore play an important role in plant growth promotion in metalliferous areas, thereby improving bioremediation processes. However, in addition to their primary function in iron mobilization, siderophores also have the capacity to chelate other heavy metals, such as Al(3+), Zn(2+), Cu(2+), Pb(2+) and Cd(2+), that can affect homeostasis and the heavy metal tolerance of microorganisms. The main goal of our study was to select the most efficient siderophore-producing bacterial strains isolated from the roots (endophytes) and rhizosphere of Betula pendula L. and Alnus glutinosa L. growing at two heavy metal contaminated sites in southern Poland. Siderophore biosynthesis of these strains in the presence of increasing concentrations of Cd(2+) (0, 0.5, 1, 2 and 3 mM) under iron-deficiency conditions was analysed using spectrophotometric chemical tests for hydroxamates, catecholates and phenolates, as well as the separation of bacterial siderophores by HPLC and characterization of their structure by UHPLC-QTOF/MS. We proved that (i) siderophore-producing bacterial strains seems to be more abundant in the rhizosphere (47%) than in root endophytes (18%); (ii) the strains most effective at siderophore synthesis belonged to the genus Streptomyces and were able to secrete three types of siderophores under Cd(2+) stress: hydroxamates, catecholates and phenolates; (iii) in general, the addition of Cd(2+) enhanced siderophore synthesis, particularly ferrioxamine B synthesis, which may indicate that siderophores play a significant role in tolerance to Cd(2+) in Streptomyces sp.
根际和内生细菌是众所周知的铁载体产生菌，铁载体是一种螯合三价铁（Fe(3+)）的有机化合物，因此在富含金属的地区对植物生长有促进作用，从而改善生物修复过程。然而，除了在铁动员中的主要功能外，铁载体还具有螯合其他重金属的能力，如 Al(3+)、Zn(2+)、Cu(2+)、Pb(2+)和 Cd(2+)，这些重金属会影响微生物的内稳态和重金属耐受性。我们研究的主要目标是从生长在波兰南部两个重金属污染地点的银桦（Betula pendula L.）和桤木（Alnus glutinosa L.）的根部（内生菌）和根际中选择最有效的产铁载体细菌菌株。在缺铁条件下，用分光光度化学试验分析了这些菌株在 Cd(2+)浓度（0、0.5、1、2 和 3 mM）增加的情况下合成铁载体的情况，这些试验包括羟肟酸盐、儿茶酸盐和酚酸盐，以及用 HPLC 分离细菌铁载体并用 UHPLC-QTOF/MS 对其结构进行表征。我们证明了：(i) 产铁载体细菌菌株似乎在根际（47%）比在根内生菌（18%）中更丰富；(ii) 合成铁载体最有效的菌株属于链霉菌属，能够在 Cd(2+)胁迫下分泌三种类型的铁载体：羟肟酸盐、儿茶酸盐和酚酸盐；(iii) 一般来说，添加 Cd(2+)会增强铁载体的合成，特别是铁氧肟酸盐 B 的合成，这表明铁载体在链霉菌属耐受 Cd(2+)中发挥了重要作用。
