Department of Geology, National Museum of Natural Sciences (MNCN-CSIC), 28006 Madrid, Spain.
Department of Biology and Geology, University of Almeria, 04120 Almeria, Spain.
Sci Total Environ. 2023 Nov 1;897:165218. doi: 10.1016/j.scitotenv.2023.165218. Epub 2023 Jul 6.
In the absence of sunlight, caves harbor a great diversity of microbial colonies to extensive biofilms with different sizes and colors visible to the naked eye. One of the most widespread and visible types of biofilm are those with yellow hues that can constitute a serious problem for the conservation of cultural heritage in many caves, such as Pindal Cave (Asturias, Spain). This cave, declared a World Heritage Site by UNESCO for its Paleolithic parietal art, shows a high degree of development of yellow biofilms that represents a real threat to the conservation of painted and engraved figures. This study aims to: 1) identify the microbial structures and the most characteristic taxa composing the yellow biofilms, 2) seek the linked microbiome reservoir primarily contributing to their growth; 3) seed light on the driving vectors that contribute to their formation and determine the subsequent proliferation and spatial distribution. To achieve this goal, we used amplicon-based massive sequencing, in combination with other techniques such as microscopy, in situ hybridization and environmental monitoring, to compare the microbial communities of yellow biofilms with those of drip waters, cave sediments and exterior soil. The results revealed microbial structures related to the phylum Actinomycetota and the most characteristic bacteria in yellow biofilms, represented by the genera wb1-P19, Crossiella, Nitrospira, and Arenimonas. Our findings suggest that sediments serve as potential reservoirs and colonization sites for these bacteria that can develop into biofilms under favorable environmental and substrate conditions, with a particular affinity for speleothems and rugged-surfaced rocks found in condensation-prone areas. This study presents an exhaustive study of microbial communities of yellow biofilms in a cave, which could be used as a procedure for the identification of similar biofilms in other caves and to design effective conservation strategies in caves with valuable cultural heritage.
在缺乏阳光的情况下，洞穴中存在着大量微生物菌落，形成广泛的生物膜，肉眼可见不同大小和颜色的生物膜。最广泛和可见的生物膜类型之一是那些带有黄色调的生物膜，它们可能对许多洞穴的文化遗产保护构成严重问题，例如西班牙阿斯图里亚斯的平达尔洞穴。这个洞穴因其旧石器时代的壁画艺术而被联合国教科文组织宣布为世界遗产，展示了高度发达的黄色生物膜，这对绘画和雕刻图像的保护构成了真正的威胁。本研究旨在：1）鉴定构成黄色生物膜的微生物结构和最具特征的分类群；2）寻找主要促进其生长的相关微生物库；3）阐明有助于其形成的驱动因素，并确定其后续的增殖和空间分布。为了实现这一目标，我们使用基于扩增子的大规模测序，结合显微镜、原位杂交和环境监测等其他技术，比较了黄色生物膜与滴水、洞穴沉积物和外部土壤的微生物群落。结果揭示了与放线菌门相关的微生物结构，以及黄色生物膜中最具特征的细菌，代表属为 wb1-P19、十字杆菌属、硝化螺旋菌属和阿伦伊门菌属。我们的研究结果表明，沉积物可能是这些细菌的潜在储库和定植场所，这些细菌可以在有利的环境和基质条件下发育成生物膜，对易凝结地区的石笋和粗糙表面的岩石有特殊的亲和力。本研究对洞穴中黄色生物膜的微生物群落进行了详尽的研究，可为其他洞穴中类似生物膜的鉴定和具有宝贵文化遗产的洞穴的有效保护策略提供依据。
