Transcriptional and metabolic stasis define desiccation-induced dormancy in the soil bacterium Arthrobacter sp. AZCC_0090 until water vapor initiates resuscitation
Microbes inhabiting soils experience periodic water deprivation. The effects of desiccation on DNA, protein, and membrane integrity are well-described. However, the effects of drying and rehydration on the composition of cellular RNA and metabolites are still poorly understood. Here, we describe how slow drying and rehydration with water vapor influence the composition of RNAs and metabolites in a soil Arthrobacter. Drying reduced cultivability relative to hydrated controls, but rehydration of dried cells with water vapor restored cultivability. The fraction of 16S and 23S rRNA to the total RNA pool was constant throughout the experiment, irrespective of treatment. mRNA profiles were invariant in desiccated cells, changing only in response to drying or rehydration. Six transcriptional modules were identified that showed distinct expression patterns in desiccated-rehydrated samples, relative to hydrated controls, including desiccation-responsive and rehydration-specific profiles. Targeted metabolomics also showed a static metabolic state during desiccation. A cluster of metabolites enriched in ribonucleosides and nucleobases was responsive to desiccation and rehydration. Collectively, these results are consistent with the relative stability of mRNA and metabolite profiles in desiccated Arthrobacter. These results imply that stable mRNA in dry dormant cells and intracellular RNA recycling may obscure interpretations of RNA-based environmental analyses that use RNA as a marker of microbial activity. Overall design: This study examines transcriptional responses to desiccation stress and recovery in Arthrobacter sp. AZCC_0090  through a 16-day time-course RNA-seq experiment. Control samples were maintained at constant 100% relative humidity throughout the experiment, while treatment samples underwent controlled desiccation: 100% RH for days 0-2, gradual drying to 65% RH between days 2-8, further drying to 25% RH between days 8-14, followed by rehydration to 100% RH between days 14-16. RNA samples were collected at four critical time points (days 2, 8, 14, and 16) from both control and treatment groups, yielding eight sample conditions that capture initial desiccation response, progressive dehydration stress, severe desiccation, and cellular recovery upon rehydration.