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Abstract Nitrogen isotope (δ¹⁵N) values in ancient rocks have been used to interpret the presence of nitrogen metabolisms and fixed N availability across the Archean and Paleoproterozoic eons. However, how δ¹⁵N signals produced by nitrogen metabolisms of microbial communities, the impact of the geochemical environments they live in on those signals, and the fidelity of those signals through preservation in the rock record have not been fully constrained and validated. Thus, it is imperative to study modern microbial systems to test the validity of using δ¹⁵N signals produced by microbial communities to interpret what geochemical environments and nitrogen metabolisms influenced the production of those signals. Hydrothermal systems are an ideal place to examine the biotic and abiotic factors that impact δ¹⁵N signals—physical processes generate geochemical environments with wide ranges of fixed N availability and the physicochemical environments exclude multicellular eukaryotic organisms. Previous work has demonstrated the presence of nitrogen fixation genes in microbial communities across a range of temperature (16–89°C) and pH (1.9–9.8) gradients. Here, we test the validity and fidelity of using microbial community δ¹⁵N signals as indicators of geochemical environment and nitrogen metabolisms (specifically, biological nitrogen fixation) present in eight hydrothermal systems across Yellowstone National Park. Our results suggest that δ¹⁵N values measured in the ancient rock record can provide information about the N cycling and prevailing environmental conditions during deposition, but only if viewed within appropriate context. 

Abstract Cyanobacteria are important targets for biotechnological applications due to their ability to grow in a wide variety of environments, rapid growth rates, and tractable genetic systems. They and their bioproducts can be used as bioplastics, biofertilizers, and in carbon capture and produce important secondary metabolites that can be used as pharmaceuticals. However, the photosynthetic process in cyanobacteria can be limited by a wide variety of environmental factors such as light intensity and wavelength, exposure to UV light, nutrient limitation, temperature, and salinity. Carefully considering these limitations, modifying the environment, and/or selecting cyanobacterial species will allow cyanobacteria to be used in biotechnological applications. 

ABSTRACT With more than 5500 detected exoplanets, the search for life is entering a new era. Using life on Earth as our guide, we look beyond green landscapes to expand our ability to detect signs of surface life on other worlds. While oxygenic photosynthesis gives rise to modern green landscapes, bacteriochlorophyll-based anoxygenic phototrophs can also colour their habitats and could dominate a much wider range of environments on Earth-like exoplanets. Here, we characterize the reflectance spectra of a collection of purple sulfur and purple non-sulfur bacteria from a variety of anoxic and oxic environments. We present models for Earth-like planets where purple bacteria dominate the surface and show the impact of their signatures on the reflectance spectra of terrestrial exoplanets. Our research provides a new resource to guide the detection of purple bacteria and improves our chances of detecting life on exoplanets with upcoming telescopes. Our biological pigment data base for purple bacteria and the high-resolution spectra of Earth-like planets, including ocean worlds, snowball planets, frozen worlds, and Earth analogues, are available online, providing a tool for modellers and observers to train retrieval algorithms, optimize search strategies, and inform models of Earth-like planets, where purple is the new green. 

This data has been generated by Dr. Jeff R. Havig and Dr. Trinity L. Hamilton, Dept. of Plant and Microbial Biology, University of Minnesota. The data compiled in this spreadsheet represents water geochemistry and biofilm molecular data collected under Yellowstone Permit YELL-2022-SCI-7020, used for submitted publication "Between a Rock and a Soft Place: Biomass δ15N Values of Hot Spring Microbial Communities and Their Potential for Preservation in the Rock Record", submitted March, 2024 to JRG Biogeosciences by Havig and Hamilton. Any publications that use this data are requested to cite the final accepted paper.