Sprecher
Beschreibung
Biofilms promote the preservation of organic material by encasing decaying tissues, forming a protective matrix over soft tissue, facilitating mineral precipitation, and slowing down decay. Despite numerous studies on the influence of microbial biofilms on animal fossilization, little is known about the role of microbial biofilms on leaves that may lead to the formation of leaf compressions. However, with genomic sequencing and bioinformatic analyses, it is now possible to identify and characterize the microbes involved in leaf biofilms, as well as to document shifts in community composition under different environmental conditions. Here we present a series of a dozen decay experiments investigating the role of bacterial taxa, sediment types, and oxygen conditions on leaf biofilms in natural freshwater pond conditions or in lab aquaria, which we carried out over the course of five years. We ran the decay experiments with Equisetum shoots and the foliage of ferns, Ginkgo, conifers, water lilies, evergreen and deciduous dicots, including green, yellow, and red pigmented leaves. Analytical tools and bioinformatic analyses were applied, including sequencing (16s rRNA, ITS, metagenomics), light microscopy, SEM, EDX, ASV richness, Shannon Index, NMDS statistics, ordination plots, correlation plots, and Venn diagrams. In summary, biofilms readily form on all freshwater-submerged leaves, although some taxa naturally produce thicker biofilms. Biofilms rapidly shift in taxonomic composition over days and in response to substrate, oxygen conditions, and water chemistry. Good promoters of biofilm production and incipient mineralization are the bacterial genera of Desulfovibrio, Tolumonas, Shewanella, pond mud, montmorillonite clay, and anaerobic conditions.