Department of Chemistry, Materials and Chemical Engineering "Giulio Natta", Politecnico di Milano and INSTM, Italy.
Department of Food, Environmental and Nutrition Sciences, Università degli Studi di Milano, Milan, Italy.
Sci Total Environ. 2018 Oct 15;639:1480-1490. doi: 10.1016/j.scitotenv.2018.05.277. Epub 2018 May 29.
Stone architectural heritage exposed outdoor represents a challenging habitat for biological growths; nevertheless, biocolonization on heritage structure is ubiquitous and represents a major mechanism of alteration. However, the identification of specific microorganisms with known reactivity towards the stone substrate does not necessarily imply that a biodeterioration process is in progress and, in specific conditions, bioprotection effects have been highlighted as a result of colonization. The main objective of the present research is to evaluate the biofilm formation on different lithotypes exposed to similar environmental polluted conditions, and to investigate whether the presence of subaerial biofilms can be associated to an increased magnitude of deterioration of the colonized surfaces with respect to the not colonized ones. In particular, the research examines the extensive biological colonization of the stone surfaces of the façade of the Cathedral of Monza (Italy). Four metamorphic stones widely used in the façade and showing rather different compositional, mineralogical and microstructural features were studied. The state of conservation of the stones was characterized under the mineralogical and compositional point of view by X-ray diffraction and Fourier Transformed infrared analysis. The microstructure of colonized substrates and of reference not colonized ones was studied by means of optical and electron microscopy, to comparatively evaluate the damage extent and weathering patterns in both conservative conditions. The structure and the architecture of biofilms growing on different lithic surfaces were investigated by CLSM in both fluorescence and reflection modes. Captured images were analyzed for 3D reconstructions of biofilm samples. The biovolumes were also calculated to estimate the total biomass. The results indicate that the four lithotypes showed different colonization extents. However, even in presence of extensive biological growth, chemical-physical deterioration mechanisms caused by environmental exposure were largely responsible for deterioration. A relationship between compositional and surface morphological features and biocolonization was also observed.
暴露于户外的石材建筑遗产代表了生物生长极具挑战性的生境；然而，在遗产结构上的生物定殖是普遍存在的，并且是改变的主要机制。然而，鉴定对石材基质具有已知反应性的特定微生物并不一定意味着生物降解过程正在进行，并且在特定条件下，由于定殖，已经强调了生物保护作用。本研究的主要目的是评估暴露于相似污染环境条件下的不同岩性类型上的生物膜形成，以及研究表面是否存在气生生物膜会与被定殖表面相对于未被定殖表面的更大程度的劣化相关联。特别是，研究考察了蒙扎大教堂（意大利）外立面上石材表面的广泛生物定殖。研究了四种广泛用于外墙且具有相当不同组成、矿物学和微观结构特征的变质岩。通过 X 射线衍射和傅里叶变换红外分析，从矿物学和组成的角度来描述石材的保存状况。通过光学和电子显微镜研究了被定殖和未被定殖基质的微观结构，以在两种保守条件下比较评估损坏程度和风化模式。通过 CLSM 在荧光和反射模式下研究了不同岩石表面上生物膜的结构和架构。捕获的图像被分析用于生物膜样品的 3D 重建。还计算了生物量以估计总生物量。结果表明，四种岩性类型表现出不同的定殖程度。然而，即使存在广泛的生物生长，环境暴露引起的化学物理劣化机制也是造成劣化的主要原因。还观察到了组成和表面形态特征与生物定殖之间的关系。
