Assessment of microbiota present on a Portuguese historical stone convent using high-throughput sequencing approaches

Abstract

The study performed on the stone materials from the Convent of Christ revealed the presence of a complex microbial ecosystem, emphasizing the determinant role of microorganisms on the biodecay of this built cultural heritage. In this case study, the presence of Rubrobacter sp., Arthrobacter sp., Roseomonas sp., and Marinobacter sp. seems to be responsible for colored stains and biofilm formation while Ulocladium sp., Cladosporium sp., and Dirina sp. may be related to structural damages. The implementation of high-throughput sequencing approaches on the Convent of Christ's biodecay assessment allowed us to explore, compare, and characterize the microbial communities, overcoming the limitations of culture-dependent techniques, which only identify the cultivable population. The application of these different tools and insights gave us a panoramic view of the microbiota thriving on the Convent of Christ and signalize the main biodeteriogenic agents acting on the biodecay of stone materials. This finding highlighted the importance of performing metagenomic studies due to the improvements and the reduced amount of sample DNA needed, promoting a deeper and more detailed knowledge of the microbiota present on these dynamic repositories that support microbial life. This will further enable us to perform prospective studies in quarry and applied stone context, monitoring biogenic and nonbiogenic agents, and also to define long-term mitigation strategies to prevent biodegradation/biodeterioration processes.

Keywords: biocolonization; biodegradation/biodeterioration; biodeteriogenic activity; metagenomic DNA; microbiota assessment; stone material biodecay.

FIGURE 1

Chapter Window (a), Primitive Cloister (b), and 1st floor of the Main Cloister (c) from Convent of Christ whose biodecay was assessed

FIGURE 2

Analysis of stone microfragments from the Manueline Window (a) and the Main Cloister (b) of the Convent of Christ, by SEM observation in back‐scattered mode (a₁ and b₁) and EDX 2D elemental maps (a_2–3 and b_2–3) with individual element distribution of calcium (Ca), silicon (Si), carbon (C), nitrogen (N), oxygen (O), and sulfur (S)

FIGURE 3

SEM micrographs showing microalgae (b, c, d, g, h), cyanobacteria (a, c, d) bacteria (c, d, g, h), and filamentous fungi (a, e, f) proliferating on stone materials (Legend; a1—cyanobacteria; a2—filamentous fungi; b1—bacteria; b2—diatom; c1—yeast; c2—unidentified filamentous structure; c3—microalgae biofilm; d1—microalgae; d2—yeast; e1, f1, and f2—filamentous fungi; g1—microalgae; g2—unknown biofilm; g3—yeast; g4—bacterial biofilm; H1—microalgae and/or cyanobacteria; h2—yeast; h3—cyanobacteria; h4—biofilm)

FIGURE 4

Predominant families of prokaryote population present on the Manueline Window (MW), the Primitive Cloister (PC), and the 1st floor of the Main Cloister (MC) of the Convent of Christ

FIGURE 5

Predominant families of eukaryote population present on the Manueline Window (MW), the Primitive Cloister (PC), and the 1st floor of the Main Cloister (MC) of the Convent of Christ

FIGURE 6

Relative abundance of prokaryote and eukaryote population present on the damaged areas of the Convent of Christ, identified at genus level (a, b—Manueline Window; c, d—Primitive Cloister; e, f—1st floor of the Main Cloister)