RNA Degradation and Osmolyte Accumulation in Arthrobacter sp. Strain AZCC_0090

Abstract

Water is essential for the structural integrity and function of bacterial cells as a substrate for biomolecular synthesis, as a solvent for nutrients and wastes, and for maintaining the conformation of cellular architecture. Soil microbes commonly experience stresses associated with dehydration and rehydration in their natural environment. It is increasingly vital to understand how soil microbes are affected by increased precipitation variability and extremes given their roles as mediators of plant health, soil biogeochemistry, and contaminant remediation. In arid soils of southern Arizona, Actinobacteria often exceed 30% of the microbes in bulk soil. Well-known for their drought tolerance, field-based studies suggest Actinobacteria are metabolically active in arid soils, but the cellular mechanisms underlying desiccation tolerance of non-spore forming Actinobacteria are not well understood. To address this knowledge gap, we performed a systems biology experiment that exposed cells of a non-spore forming Actinobacteria from the genus Arthrobacter isolated near Tucson, AZ to water stress, to investigate how cell culturability, total RNA concentration, and metabolite production change along the desiccation-rehydration continuum. Our experiment compared the physiology of Arthrobacter sp. strain AZCC_0090 cells that were gradually desiccated to 25% relative humidity (RH) and rehydrated at 100% RH to cells that were continuously hydrated. Samples for culturability, total RNA content, and metabolomes were collected at four time points in both the desiccated treatment samples and the hydrated controls. Here, I show that culturability and total RNA content decreased during desiccation but returned to control levels after rehydration with water vapor. I also show that AZCC_0090 cells accumulate RNA degradation products and a cocktail of osmolytes with diverse osmoprotectant and antioxidant properties.