Microorganisms are critical in the bio-and geosphere today and certainly performed similar functions in ancient ecosystems. Bacteria, cyanobacteria, microalgae, and various fungi and fungal-like organisms constitute a major component of these ancient communities, and have been responsible for the evolution and sustainability of the ecosystems in functions ranging from decomposition to catalyzation of nutrient cycles. Despite the importance of these organisms, little is known about their interactions through geologic time. The Lower Devonian Rhynie chert Lagerstatte provides a window into the microbial interactions that took place with plants and animals approximately 400 million years ago. The fossils in this fresh water ecosystem were preserved in extraordinary detail so that it is possible to examine various levels of microbial/plant/animal interactions. To accomplish this objective PIs have formed an international research group that will examine the fossil microbes from the Rhynie chert (RC). Preliminary studies indicate that microorganisms are abundant, with many new forms and new levels of interaction present. For example, some of the associations involve fungi in certain plant organs in the form of mycorrhizae; another fungal interaction constitutes a lichen symbiosis. Other examples include cyanobacteria with fungi in plant underground organs, and bacteria in certain fungal spores. There are excellent examples of fungi in parasitic associations with plants, the latter showing specific symptoms of infection. PIs work will focus on four themes that are highly interrelated: 1) documenting the diversity of fossil microorganisms, 2) deciphering complex interactions between microorganisms and other organisms, and comparing these with modern interactions, 3) using information to constrain phylogenetic analyses based on molecular sequence data sets, 4) developing a 3-D reconstruction of the RC ecosystem, including spatial and quantitative data on the microorganisms present. The examination of these microorganisms and their associations with other organisms can be used to trace co-evolutionary processes and help to formulate hypotheses that can be designed to more fully understand the evolutionary history of ecosystems.
