Experimental biofilm-mediated mineralization of leaves

Microorganisms can colonize and form biofilms on leaves and soft tissues. The mineralization of soft tissues is influenced by biofilm development and complex microbial communities. This study aimed to develop leaf biofilms in vitro on Hedera leaves, explore the microbial community composition, and investigate conditions under which the leaf biofilms will form a mineralized surface layer.

We examined the temporal dynamics of microbial communities over three weeks under aerobic and anaerobic conditions and isolated single bacterial strains from decaying leaves to reconstitute biofilm microbial communities in the laboratory. Biofilm-covered leaf samples were collected weekly and investigated by scanning electron microscopy. We used 16S rRNA to measure microbial diversity and temporal changes in microbial communities of Hedera leaves. To characterize the conditions that lead to mineralization, the biofilm-coated leaves were exposed to different compounds that might enhance mineralization. We observed a compositional shift in bacterial communities over three weeks, with oxygen availability and incubation time influencing microbial diversity. The genera Vogesella, Tolumonas, Rhodoferax and Aeromonas were initially abundant and decreased over time. We isolated 83 bacterial strains from biofilm-coated decaying leaves in vitro. The addition of a minimum of 80mg/ml of Ca2+ concentration was found essential for mineralization, and the addition of the Shewanella sp. strain enhanced FeSx mineral formation under slightly acidic pH. These findings provide valuable insights for further investigations of leaf biofilms in the context of biomineralization and preservation.