Department of Science and High Technology, University of Insubria, Via Valleggio 11, 22100 Como, Italy.
Instituto de Recursos Naturales y Agrobiologıá de Sevilla (IRNAS-CSIC), E-41080 Seville, Spain.
Sci Total Environ. 2021 Sep 10;786:147431. doi: 10.1016/j.scitotenv.2021.147431. Epub 2021 Apr 30.
In this study we first measured the mineralization of pyrene on leaves of urban holm oak (Quercus ilex) by autochthonous microorganisms and an inoculated PAH degrading bacterium (i.e., Mycobacterium gilvum), selected as a model phyllosphere species, as well as the leaf-water (K) and leaf-air (K) partition coefficients for this chemical. Mineralization was investigated in two different experimental systems in terms of leaf and microorganism environment. Additionally, the influence on pyrene partitioning and mineralization when particulate matter (PM) was present on the leaf surface or removed was studied. Mineralization of C-labeled pyrene by autochthonous microorganisms was lower than 1% after approximately two weeks, while M. gilvum mineralized 5% to 17% of pyrene. These extents corresponded to mineralization half-lives that ranged between ~30 to ~200 days. We proposed that PM present at the leaf surface reduced the accumulation of pyrene by inner compartments (cuticle) distantly located from microbial cells and enhanced the bioaccessibility of pyrene, speeding up microbial activity and therefore mineralization. These results highlight that plant-phyllosphere microorganism interaction is more complex than currently established and deserves additional studies to further comprehend the air purification ecosystem service of phyllosphere microorganisms.
在这项研究中，我们首先通过土著微生物和接种的多环芳烃降解细菌（即分枝杆菌）来测量城市圣栎（Quercus ilex）叶片上芘的矿化作用，选择分枝杆菌作为模式叶际物种，以及该化学物质的叶水（K）和叶气（K）分配系数。从叶片和微生物环境两个不同的实验系统研究了矿化作用。此外，还研究了当叶片表面存在或去除颗粒物（PM）时对芘分配和矿化的影响。在大约两周后，土著微生物对 C 标记的芘的矿化作用低于 1%，而分枝杆菌则矿化了 5%至 17%的芘。这些程度对应于矿化半衰期在30 至200 天之间。我们提出，叶片表面存在的 PM 减少了远离微生物细胞的内部隔室（角质层）中芘的积累，并提高了芘的生物可利用性，加速了微生物的活性，从而加速了矿化作用。这些结果表明，植物-叶际微生物的相互作用比目前所建立的更为复杂，值得进一步研究，以进一步了解叶际微生物的空气净化生态系统服务。
