Quorum sensing between phylogenetically ancient Cyanobacteria and heterotrophic Bacteria in a simulated early Mars atmosphere

Communication may have been the key to life's success and persistence on planet Earth. Understanding how different environmental conditions impact bacterial life, and what role communication may play in metabolic processes, is necessary for the fields of astrobiology and space microbiology. N-acyl homoserine lactone based quorum sensing (AHL-QS), a form of community controlled gene expression that was likely established early in microbial evolution, was investigated in co-cultures of a deeply branching, phylogenetically ancient cyanobacterium, Gloeobacter violaceus, and heterotrophic consortia under contemporary terrestrial and simulated early Mars atmospheric conditions. The type and relative concentrations of AHLs produced by heterotrophic consortia were determined, along with differential gene expression by RNAseq when exogenous AHLs were applied and under simulated early Mars atmospheric conditions. The results show that G. violaceus, an early-Earth photoautotrophic representative, and heterotrophic consortia have a vast genomic potential for AHL-QS, and that AHL-QS is likely underrepresented across phyla. Results also show that the consortium significantly differentially regulates genes in response to early Mars atmospheric conditions and may participate in AHL-QS by differentially regulating genes in response to N-3-oxo-dodecanoyl-L-Homoserine lactone. Understanding how microbial consortia respond to Mars atmospheric conditions is critical for planetary protection and could identify areas in which life may have existed, or still exists, on Mars, advance our understanding of life and its ability to survive in extreme conditions, and improve upon our understanding of the origin and evolution of life on Earth.