BayCEER Workshop 2023

Soil microbial composition and replication directly respond to the presence of biocides from building materials

P 4.6 in Thinking sharp: Insights from inbetween

Biocides are used in building materials to protect the building against microbial colonization and biodeterioration. However, these biocides are introduced by gradual leaching into soils in proximity of the buildings. The effects of biocides frequently used in facade renders and paints on the soil microbiome are still unknown. Therefore, the study aimed to elucidate the effect of three individual biocides and its four combinations of two or three biocides on the bacterial and fungal community composition and proliferation activity. Moreover, soil chemical parameters, biocide, and biocidal degradation product concentrations were determined at the beginning and after 28 d of incubation and compared to the control. Bromodeoxyuridine  immunocapture technique was used in combination with pair-end Illumina sequencing to differentiate the total and active bacterial and fungal microbiomes. In addition, bacterial and fungal gene copy number were quantified via Real-Time PCR analysis.

The biocidal treatment did not alter the soil's chemical properties significantly. In turn, the biocidal treatment significantly decreased the total gene copy numbers of both fungal and bacterial community composition. At the same time total bacterial and fungal microbiomes did not significantly change between the biocidal treatments, but the active microbiomes of both bacteria and fungi. While Desulfotomaculum, and Methyloversatilis decreased, well-known herbicide degraders such as members of the genus Arthrobacter increased. Similarly, shifts were found in the fungal community composition, which will be shown in detail by an indicator species analysis.

Our results show that biocides as preservatives of façade renders and paints lead to a significant alteration in the active soil microbial community without dramatic shifts in the soil's chemical properties. Therefore, the addition of even low biocide concentration led to a distortion in the activity patterns, which should be characterized with the run-off of façades in future.

Keywords: Soil microbiome, biocides, toxicity