Fernández-Juárez Víctor, López-Alforja Xabier, Frank-Comas Aida, Echeveste Pedro, Bennasar-Figueras Antoni, Ramis-Munar Guillem, Gomila Rosa María, Agawin Nona S R
Marine Ecology and Systematics (MarES), Department of Biology, University of the Balearic Islands, Palma de Mallorca, Spain.
Instituto de Ciencias Naturales Alexander von Humboldt, Universidad de Antofagasta, Antofagasta, Chile.
Front Microbiol. 2021 Jan 20;11:581118. doi: 10.3389/fmicb.2020.581118. eCollection 2020.
Little is known about the direct effects of microplastics (MPs) and their organic additives on marine bacteria, considering their role in the nutrient cycles, e.g., N-cycles through the N-fixation, or in the microbial food web. To fill this gap of knowledge, we exposed marine bacteria, specifically diazotrophs, to pure MPs which differ in physical properties (e.g., density, hydrophobicity, and/or size), namely, polyethylene, polypropylene, polyvinyl chloride and polystyrene, and to their most abundant associated organic additives (e.g., fluoranthene, 1,2,5,6,9,10-hexabromocyclododecane and dioctyl-phthalate). Growth, protein overproduction, direct physical interactions between MPs and bacteria, phosphorus acquisition mechanisms and/or N-fixation rates were evaluated. Cyanobacteria were positively affected by environmental and high concentrations of MPs, as opposed to heterotrophic strains, that were only positively affected with high concentrations of ~120 μm-size MPs (detecting the overproduction of proteins related to plastic degradation and C-transport), and negatively affected by 1 μm-size PS beads. Generally, the organic additives had a deleterious effect in both autotrophic and heterotrophic bacteria and the magnitude of the effect is suggested to be dependent on bacterial size. Our results show species-specific responses of the autotrophic and heterotrophic bacteria tested and the responses (beneficial: the "good," deleterious: the "bad" and/or both: the "double-sword") were dependent on the type and concentration of MPs and additives. This suggests the need to determine the threshold levels of MPs and additives concentrations starting from which significant effects can be observed for key microbial populations in marine systems, and these data are necessary for effective environmental quality control management.
考虑到微塑料（MPs）及其有机添加剂在营养循环（例如通过固氮作用的氮循环）或微生物食物网中的作用，人们对它们对海洋细菌的直接影响知之甚少。为了填补这一知识空白，我们将海洋细菌，特别是固氮菌，暴露于物理性质（如密度、疏水性和/或大小）不同的纯MPs中，即聚乙烯、聚丙烯、聚氯乙烯和聚苯乙烯，以及它们最丰富的相关有机添加剂（如荧蒽、1,2,5,6,9,10-六溴环十二烷和邻苯二甲酸二辛酯）。评估了生长、蛋白质过量产生、MPs与细菌之间的直接物理相互作用、磷获取机制和/或固氮率。蓝细菌受到环境浓度和高浓度MPs的积极影响，而异养菌株则相反，它们仅在高浓度的约120μm大小的MPs（检测到与塑料降解和碳运输相关的蛋白质过量产生）下受到积极影响，并受到1μm大小的聚苯乙烯珠的负面影响。一般来说，有机添加剂对自养和异养细菌都有有害影响，并且这种影响的程度被认为取决于细菌的大小。我们的结果表明，所测试的自养和异养细菌具有物种特异性反应，并且这些反应（有益：“好”，有害：“坏”和/或两者兼具：“双刃剑”）取决于MPs和添加剂的类型和浓度。这表明需要确定MPs和添加剂浓度的阈值水平，从该水平开始可以观察到对海洋系统中关键微生物种群的显著影响，并且这些数据对于有效的环境质量控制管理是必要的。
