Urban endoliths: incidental microbial communities occurring inside concrete

Abstract

<abstract> <p>Concrete is now a prevalent type of synthetic rock, and its production and usage have major environmental implications. Yet, assessments of ordinary concrete have rarely considered that concrete itself is potential habitat for a globally important microbial guild, the endolithic microbes, which live inside rocks and other mineralized substrates. We sought evidence that many common concrete structures harbor endolithic microbial communities and that these communities vary widely depending on the conditions imposed by the concrete. In Summer 2022, we obtained samples from various concrete structures found throughout Lubbock, Texas, USA and subjected the internal (non-surface) portions of each sample to controlled microbial life detection tests including culture tests, DNA quantifications, DNA amplification tests, and ATP assays. The great preponderance of positive life detection results from our concrete samples suggests that most modern concrete hosts cryptic endolith communities composed of bacteria, sometimes co-occurring with fungi and/or archaea. Moreover, many of these microbes are viable, culturable, and identifiable via genetic analysis. Endolith signatures varied widely across concrete samples; some samples only yielded trace evidence of possibly dormant microbes while other samples contained much more microbial biomass and diversity, on par with some low-biomass soils. Pre-cast masonry units and fragments of poured concrete found underwater generally had the most endolith signatures, suggesting that concrete forms and environmental positioning affect endolithy. Endolith biosignatures were generally greater in less dense and less alkaline concrete samples. So, concrete endolith communities may be as ubiquitous and diverse as the concrete structures they inhabit. We propose further research of concrete endoliths to help clarify the role of modern concrete in our rapidly urbanizing biosphere.</p> </abstract>

Metagenomic Analysis of a Concrete Bridge Reveals a Microbial Community Dominated by Halophilic Bacteria and Archaea

“…Also somewhat surprising was the low fungal abundance. Fungi, particularly lichens, can colonize concrete surfaces ( 44 ), and a few have been isolated from concrete ( 45 ). It is possible that some of the nearly 40% of reads that could not be classified belong to poorly characterized fungal groups, since databases of fungal genomes lag significantly behind those for Bacteria and Archaea ( 46 ).…”

Bacterial Treatment of Recycled Concrete Aggregate

“…Bacteria are ubiquitous in nature and can be found in extreme environments, of which concrete should be considered one, due to the increased alkalinity and low water activity. A study found that concrete of varying composition and location was found to have predominantly bacterial DNA [75]. This suggests endolithic bacteria are able to survive in concrete and could be a source of SSB.…”