Unveiling metabolic pathways involved in the extreme desiccation tolerance of an Atacama cyanobacterium

Abstract

AbstractGloeocapsopsis dulcisstrain AAB1 is an extremely xerotolerant cyanobacterium isolated from the Atacama Desert (i.e., the driest and oldest desert on Earth) that holds astrobiological significance due to its surprising ability to biosynthesize compatible solutes at ultra-low water activities. We sequenced and assembled theG. dulcisgenome de novo using a combination of long- and short-read sequencing, which resulted in high-quality consensus sequences of the chromosome and two plasmids. We leveraged theG. dulcisgenome to generate a genome-scale metabolic model (iGd895) to simulate growthin silico. iGd895represents, to our knowledge, the first genome-scale metabolic reconstruction developed for an extremely xerotolerant cyanobacterium. The model's predictive capability was assessed by comparing thein silicogrowth rate within vitrogrowth rates ofG. dulcis, in addition to the synthesis of trehalose.iGd895allowed us to explore key metabolic processes such as essential pathways for water-stress tolerance, and significant alterations to reaction flux distribution and metabolic network reorganization resulting from water limitation. Our study provides insights into the potential metabolic strategies employed byG. dulcis, emphasizing the crucial roles of compatible solutes, metabolic water, energy conservation, and the precise regulation of reaction rates in their adaptation to water stress.