Kiledal E Anders, Keffer Jessica L, Maresca Julia A
Department of Biological Sciences, University of Delaware, Newark, Delaware, USA.
Department of Civil and Environmental Engineering, University of Delaware, Newark, Delaware, USA.
mSystems. 2021 May 4;6(3):e01153-20. doi: 10.1128/mSystems.01153-20.
Concrete is an extreme but common environment and is home to microbial communities adapted to alkaline, saline, and oligotrophic conditions. Microbes inside the concrete that makes up buildings or roads have received little attention despite their ubiquity and capacity to interact with the concrete. Because concrete is a composite of materials which have their own microbial communities, we hypothesized that the microbial communities of concrete reflect those of the concrete components and that these communities change as the concrete ages. Here, we used a 16S amplicon study to show how microbial communities change over 2 years of outdoor weathering in two sets of concrete cylinders, one prone to the concrete-degrading alkali-silica reaction (ASR) and the other having the risk of the ASR mitigated. After identifying and removing taxa that were likely laboratory or reagent contaminants, we found that precursor materials, particularly the large aggregate (gravel), were the probable source of ∼50 to 60% of the bacteria observed in the first cylinders from each series. Overall, community diversity decreased over 2 years, with temporarily increased diversity in warmer summer months. We found that most of the concrete microbiome was composed of , , and , although community composition changed seasonally and over multiyear time scales and was likely influenced by environmental deposition. Although the community composition between the two series was not significantly different overall, several taxa, including , , , , , and , appear to be associated with ASR. Concrete is the most-used building material in the world and a biologically extreme environment, with a microbiome composed of bacteria that likely come from concrete precursor materials, aerosols, and environmental deposition. These microbes, though seeded from a variety of materials, are all subject to desiccation, heating, starvation, high salinity, and very high pH. Microbes that survive and even thrive under these conditions can potentially either degrade concrete or contribute to its repair. Thus, understanding which microbes survive in concrete, under what conditions, and for how long has potential implications for biorepair of concrete. Further, methodological pipelines for analyzing concrete microbial communities can be applied to concrete from a variety of structures or with different types of damage to identify bioindicator species that can be used for structural health monitoring and service life prediction.
混凝土是一种极端但常见的环境，是适应碱性、盐碱和贫营养条件的微生物群落的家园。尽管构成建筑物或道路的混凝土内部的微生物无处不在且有与混凝土相互作用的能力，但它们很少受到关注。由于混凝土是由具有自身微生物群落的材料组成的复合材料，我们推测混凝土的微生物群落反映了混凝土成分的微生物群落，并且这些群落会随着混凝土的老化而变化。在这里，我们使用16S扩增子研究来展示两组混凝土圆柱体在户外风化2年期间微生物群落是如何变化的，其中一组容易发生降解混凝土的碱-硅酸反应（ASR），另一组减轻了ASR的风险。在识别并去除可能是实验室或试剂污染物的分类群后，我们发现前体材料，特别是大骨料（砾石），可能是每个系列中第一个圆柱体中约50%至60%观察到的细菌的来源。总体而言，群落多样性在2年内下降，在较温暖的夏季月份多样性暂时增加。我们发现大多数混凝土微生物组由 、 和 组成，尽管群落组成随季节和多年时间尺度而变化，并且可能受环境沉降影响。尽管两个系列之间的群落组成总体上没有显著差异，但包括 、 、 、 、 和 在内的几个分类群似乎与ASR有关。混凝土是世界上使用最广泛的建筑材料，也是一个生物极端环境，其微生物组由可能来自混凝土前体材料、气溶胶和环境沉降的细菌组成。这些微生物虽然来自多种材料，但都面临干燥、加热、饥饿、高盐度和非常高的pH值。在这些条件下存活甚至茁壮成长的微生物可能会降解混凝土或有助于其修复。因此，了解哪些微生物在混凝土中存活、在什么条件下存活以及存活多长时间对混凝土的生物修复具有潜在意义。此外，用于分析混凝土微生物群落的方法管道可以应用于来自各种结构或具有不同类型损坏的混凝土，以识别可用于结构健康监测和使用寿命预测的生物指示物种。
