Project description:Biological soil crusts (BSCs) are cyanobacteria-dominated microbial communities that cover extensive portions of the world’s arid and semi-arid deserts. The infrequent periods of hydration are often too short to allow for dormancy strategies based on sporulation; consequently, survival is based on the unique capabilities of vegetative cells to resuscitate from and re-enter a stress resistant dormant state, one of which is migration within the crust layers in response to hydration. In this study, we sought to characterize the events that govern the emergence of the dominant cyanobacterium from dormancy, its subsequent growth, and the events triggered by re-desiccation and a transition back to dormant state. We performed a 48 hour laboratory wetting experiment of a desert BSC and tracked the response of Microcoleus vaginatus using a whole genome transcriptional time-course including night/day periods. This allowed the identification of genes with a diel expression pattern, genes involved uniquely in the signaling after hydration and those that contribute primarily to desiccation preparation. Desert BSC samples collected from Moab, UT, were hydrated over a period of 48 hours followed by drying induced by removal of water. At periodic times soil samples were harvested and used for RNA extraction and whole genome expression analysis using an expression array representing genes from two strains of M. vaginatus (PCC 9802 and FGP-2)
Project description:Biological soil crusts (BSCs) are cyanobacteria-dominated microbial communities that cover extensive portions of the world’s arid and semi-arid deserts. The infrequent periods of hydration are often too short to allow for dormancy strategies based on sporulation; consequently, survival is based on the unique capabilities of vegetative cells to resuscitate from and re-enter a stress resistant dormant state, one of which is migration within the crust layers in response to hydration. In this study, we sought to characterize the events that govern the emergence of the dominant cyanobacterium from dormancy, its subsequent growth, and the events triggered by re-desiccation and a transition back to dormant state. We performed a 48 hour laboratory wetting experiment of a desert BSC and tracked the response of Microcoleus vaginatus using a whole genome transcriptional time-course including night/day periods. This allowed the identification of genes with a diel expression pattern, genes involved uniquely in the signaling after hydration and those that contribute primarily to desiccation preparation.
Project description:Enterobacter sp. SA187 is a facultative endophytic bacterium conferring multi-abiotic stress tolerance to various plant hosts. Upon interaction with plant tissues, a significant proportion of the typically yellow SA187 lose pigmentation. This phenotypic shift becomes more prominent with extended host plant colonization and under stress conditions, such as salinity. To explore the underlying mechanisms and ecological significance of this variation, we employed genome sequencing, comparative genomics, transcriptomics, and metabolic characterization. In all white SA187 variants, weidentified consistent point mutations in the rpoS gene, which encodes a global regulatory sigma factor. These rpoS loss-of-function mutations lead to alterations in gene regulation, affecting growth, morphology, biofilm formation, motility, oxidative stress responses and carotenoid production. Notably, the rpoS mutants demonstrated enhanced adaptability from a free living to an endophytic life style. Whereas the desert soil is characterized by highly alkaline conditions, the apoplast of the host plant is an acidic environment accompanied with the availability of distinct carbon sources. RpoS mutants allow life in the acidic and sucrose-rich apoplastic compartment, underscoring the role of genetic variation in bacterial adaptation to colonize plants.