Abstract EANA2024-62

Recent advancements in next-generation sequencing technologies have profoundly changed our understanding of microorganisms inhabiting diverse environments, including the Earth's atmosphere. These developments have uncovered the presence of microorganisms in extreme conditions, suggesting the possibility of life beyond our planet. Studying atmospheric microorganisms can enhance our knowledge of Earth's ecosystem and support the quest for extraterrestrial life.

Our research focuses on identifying and characterizing the microbiome components present in different troposphere layers. We utilize Next Generation Sequencing data from public repositories like the Sequence Read Archive and the European Nucleotide Archive. The data undergoes quality assessment using FastQC and sequence analysis with tools such as Trimmomatic.16S rRNA sequences were annotated using Qiime2 and Silva138 databases. Metabolic pathway prediction was performed using Picrust2. 

Here, we present results where the pathways PWY-4361, PWY-6629, PWY-7090, PWY-622, PWY-5743, PWY-5744, and PWY-7024, significantly (P<0.05) more abundant in tropospheric layers above 2000 meters, represent crucial metabolic processes across various organisms. PWY-4361 participates in the methionine salvage cycle, recycling methionine in aerobic organisms. PWY-6629 synthesizes L-tryptophan, essential for protein production and neurotransmitter synthesis. PWY-7090 is involved in bacterial complex carbohydrate biosynthesis. PWY-622 covers starch biosynthesis in plants, which is crucial for energy storage. PWY-5743 and PWY-5744, part of the 3-hydroxypropanoate cycle and glyoxylate assimilation, enable green nonsulfur bacteria to fix CO2 and integrate it into central metabolism. PWY-7024 integrates these processes, enhancing carbon fixation efficiency. Their prevalence at high altitudes suggests their importance in the metabolic adaptation of microorganisms to these environments.

These pathways indicate that bacteria in the upper troposphere are equipped to handle the low nutrient availability and, high UV radiation. Detected metabolic pathways enable bacteria to recycle essential nutrients, fix carbon, and maintain cellular integrity, thus supporting their survival and potential roles in atmospheric processes such as cloud formation and nutrient cycling.

By examining the unique microbiomes present in the various layers of Earth's troposphere, our study seeks to create methodologies and frameworks that can be applied to potential aerobiomes on other planets. Insights into the factors that sustain microbial life in Earth's atmosphere can inform the search for life on planets such as Venus, where the detection of phosphine gas suggests possible microbial activity. Understanding atmospheric microorganisms on Earth is essential for investigating the potential existence and survival strategies of extraterrestrial life. Our findings may be used in future comparative genomics analyses on species present at different atmospheric levels. Core and pan-genomes of microbes from various altitudes may be used to determine common and unique genetic elements. Additionally, phylogenetic analysis might elucidate the evolutionary relationships between these species. Functional annotation, enrichment, and network analysis categorize genes and explore microbial interactions, revealing unique adaptations, stress responses, and metabolic pathways. These insights enhance our understanding of atmospheric microbes' survival strategies and ecological roles, with implications for broader ecological and astrobiological contexts.