Coutaud Margot, Viers Jérôme, Rols Jean-Luc, Pokrovsky Oleg S
Geosciences and Environment Toulouse, Université de Toulouse, CNRS, Université Toulouse 3 Paul Sabatier (UPS), 14 Avenue Edouard Belin, 31400 Toulouse, France; Centre de Recherche sur la Biodiversité et l'Environnement (CRBE), Université de Toulouse, CNRS, Toulouse INP, 118 Route de Narbonne, 31062 Toulouse, France.
Geosciences and Environment Toulouse, Université de Toulouse, CNRS, Université Toulouse 3 Paul Sabatier (UPS), 14 Avenue Edouard Belin, 31400 Toulouse, France.
Sci Total Environ. 2025 Jan 15;960:178371. doi: 10.1016/j.scitotenv.2025.178371. Epub 2025 Jan 9.
Copper (Cu) and zinc (Zn) are two trace metals that exhibit both limiting and toxic effects on aquatic microorganisms. However, in contrast to good knowledge of these metal interactions with individual microbial cultures, the biofilm, complex natural consortium of microorganisms, remains poorly understood with respect to its control on Cu and Zn in the aquatic environments. Towards constraining the magnitude and mechanisms of Cu and Zn isotope fractionation in the presence of phototrophic biofilms composed of different proportion of diatoms, green algae and cyanobacteria, we studied long-term growth in a rotating annular bioreactor and quantified the uptake of metals and their isotope fractionation at environmentally-relevant Cu and Zn concentrations. An enrichment of the biofilm in heavy Cu isotope at the beginning of growth suggests the dominance of adsorption processes, followed by intracellular uptake leading to progressive enrichment in light isotope and an excretion of heavy isotope, likely linked to Cu(II) reduction. In the case of Zn, we evidenced only weak isotope fractionation which implies the presence of heavier isotope adsorption (notably in the case of cyanobacteria-dominated biofilm) followed by intracellular incorporation of lighter isotopes. The microbial community plays important role in overall magnitude and even direction of fractionation, suggesting sizable complexity of the processes controlling metal isotope fractionation during phototrophic biofilm growth. However, Cu and Zn isotopes during long-term metal accumulation in riverine biofilm can be used for monitoring the source of environmental pollution in aquatic systems, provided that variations within different sources exceed the natural isotopic fractionation between the biofilm and aqueous solution.
铜（Cu）和锌（Zn）是两种对水生微生物具有限制作用和毒性影响的痕量金属。然而，与对这些金属与单个微生物培养物相互作用的深入了解相比，生物膜作为微生物的复杂天然群落，在水生环境中对铜和锌的控制方面仍知之甚少。为了限制在由不同比例的硅藻、绿藻和蓝细菌组成的光合生物膜存在下铜和锌同位素分馏的程度和机制，我们在旋转环形生物反应器中研究了长期生长情况，并在与环境相关的铜和锌浓度下对金属的吸收及其同位素分馏进行了量化。生长初期生物膜中重铜同位素的富集表明吸附过程占主导，随后是细胞内吸收，导致轻同位素逐渐富集，重同位素排出，这可能与铜（II）的还原有关。对于锌，我们仅证明了微弱的同位素分馏，这意味着存在较重同位素的吸附（特别是在蓝细菌主导的生物膜情况下），随后是较轻同位素的细胞内掺入。微生物群落在分馏的总体程度甚至方向上起着重要作用，这表明在光合生物膜生长过程中控制金属同位素分馏的过程相当复杂。然而，只要不同来源之间的差异超过生物膜与水溶液之间的天然同位素分馏，河流生物膜中长期金属积累过程中的铜和锌同位素就可用于监测水生系统中的环境污染源。
