Chemical composition of material extractives influences microbial growth and dynamics on wetted wood materials

Abstract

The impact of material chemical composition on microbial growth on building materials remains relatively poorly understood. We investigate the influence of the chemical composition of material extractives on microbial growth and community dynamics on 30 different wood species that were naturally inoculated, wetted, and held at high humidity for several weeks. Microbial growth was assessed by visual assessment and molecular sequencing. Unwetted material powders and microbial swab samples were analyzed using reverse phase liquid chromatography with tandem mass spectrometry. Different wood species demonstrated varying susceptibility to microbial growth after 3 weeks and visible coverage and fungal qPCR concentrations were correlated (R² = 0.55). Aspergillaceae was most abundant across all samples; Meruliaceae was more prevalent on 8 materials with the highest visible microbial growth. A larger and more diverse set of compounds was detected from the wood shavings compared to the microbial swabs, indicating a complex and heterogeneous chemical composition within wood types. Several individual compounds putatively identified in wood samples showed statistically significant, near-monotonic associations with microbial growth, including C₁₁H₁₆O₄, C₁₈H₃₄O₄, and C₆H₁₅NO. A pilot experiment confirmed the inhibitory effects of dosing a sample of wood materials with varying concentrations of liquid C₆H₁₅NO (assuming it presented as Diethylethanolamine).

Figure 1

Fractional area of microbial growth coverage over time on 13 wood species with visible microbial growth after wetting and held at 94% RH for 3 weeks. There was no visible microbial growth on the other 17 wood species in the 3-week test period.

Figure 2

Fungal qPCR concentrations on all 30 wood species after 3 weeks of incubation at high RH.

Figure 3

Correlation between visible microbial growth coverage and fungal qPCR concentrations for the 30 tested wood species after 3 weeks of incubation at high RH.

Figure 4

Fungal relative abundance detected by ITS sequencing in 30 different wood materials (with the exception of Leopardwood, which did not yield any ITS DNA) after 3 weeks of high RH exposure. Wood species are shown in descending order of qPCR magnitude from bottom to top, and the legend is sorted by taxa prevalence.

Figure 5

Metabolomics analysis of microbial swab extracts and wood shavings: (a) Volcano plot indicating metabolites that are selectively present in either wood shaving samples (left, green dots) or in swab extract samples (right, red dots), (b) PCA plot contrasting clustering of swab extract samples (blue) and wood shavings samples (gold), (c) PCA plot for swab extract samples only, and (d) PCA plot for wood shaving samples only.

Figure 6

Chemical compounds identified (represented by molecular weight) and quantified (represented by compound integrated area) in Ponderosa Pine and White Oak wood shavings.

Figure 7

Clustering analysis of 30 wood materials by microbial growth.

Figure 8

Abundance of C₁₁H₁₆O₄ versus visible microbial growth percentage at the end of the 3-week test (Spearman rho = 0.742).

Figure 9

Abundance of C₁₈H₃₄O₄ versus fungal qPCR concentration at the end of the 3-week test (Spearman rho = 0.768).

Figure 10

Abundance of three putatively identified chemical compounds versus microbial growth outcomes at the end of the 3-week test: (a) C₁₈H₂₈O₄ versus visible growth, (b) C₁₈H₂₈O₄ versus fungal qPCR, (c) C₁₂H₁₆N₂O₁₂ versus visible growth, (d) C₁₂H₁₆N₂O₁₂ versus fungal qPCR, (e) C₆H₁₅NO versus visible growth, and (f) C₆H₁₅NO versus fungal qPCR.

Figure 11

Visible microbial growth coverage over time for Ponderosa Pine samples wetted with solutions with varying concentrations of C₆H₁₅NO: (a) tap water and (b) distilled water.