Project description:Because of their ubiquity and resistance to spacecraft decontamination, bacterial spores are considered likely potential forward contaminants on robotic missions to Mars. Thus it is important to understand their global responses to long-term exposure to space or Mars environments. As part of the PROTECT experiment, spores of B. subtilis 168 were exposed to real space conditions and to simulated martian conditions for 559 days in low Earth orbit mounted on the EXPOSE-E exposure platform outside the European Columbus module on the International Space Station. Upon return, spores were germinated, total RNA extracted and fluorescently labeled, and used to probe a custom Bacillus subtilis microarray to identify genes preferentially activated or repressed relative to ground control spores. Increased transcript levels were detected for a number of stress-related regulons responding to DNA damage (SOS response, SPβ prophage induction), protein damage (CtsR/Clp system), oxidative stress (PerR regulon) and cell envelope stress (SigV regulon). Spores exposed to space demonstrated a much broader and more severe stress response than spores exposed to simulated Mars conditions. The results are discussed in the context of planetary protection for a hypothetical journey of potential forward contaminant spores from Earth to Mars and their subsequent residence on Mars. Two-color microarrays were performed comparing germination of Space-exposed or Mars-exposed vs. ground-control (Earth) spores.
Project description:If life exists on Mars, it would face several challenges including the presence of perchlorates, which destabilize biomacromolecules by inducing chaotropic stress. However, little is known about perchlorate toxicity for microorganism on the cellular level. Here we present a proteomic investigation on the perchlorate-specific stress responses of the halotolerant yeast Debaryomyces hansenii and compare these to generally known salt stress adaptations. We found that the responses to NaCl and NaClO4-induced stresses share many common metabolic features, e.g., signaling pathways, elevated energy metabolism, or osmolyte biosynthesis. However, several new perchlorate-specific stress responses could be identified, such as protein glycosylation and cell wall remodulations, presumably in order to stabilize protein structures and the cell envelope. These stress responses would also be relevant for life on Mars, which - given the environmental conditions - likely developed chaotropic defense strategies such as stabilized confirmations of biomacromolecules and the formation of cell clusters.
Project description:Because of their ubiquity and resistance to spacecraft decontamination, bacterial spores are considered likely potential forward contaminants on robotic missions to Mars. Thus it is important to understand their global responses to long-term exposure to space or Mars environments. As part of the PROTECT experiment, spores of B. subtilis 168 were exposed to real space conditions and to simulated martian conditions for 559 days in low Earth orbit mounted on the EXPOSE-E exposure platform outside the European Columbus module on the International Space Station. Upon return, spores were germinated, total RNA extracted and fluorescently labeled, and used to probe a custom Bacillus subtilis microarray to identify genes preferentially activated or repressed relative to ground control spores. Increased transcript levels were detected for a number of stress-related regulons responding to DNA damage (SOS response, SPβ prophage induction), protein damage (CtsR/Clp system), oxidative stress (PerR regulon) and cell envelope stress (SigV regulon). Spores exposed to space demonstrated a much broader and more severe stress response than spores exposed to simulated Mars conditions. The results are discussed in the context of planetary protection for a hypothetical journey of potential forward contaminant spores from Earth to Mars and their subsequent residence on Mars.
Project description:Scaffold or matrix attachment regions (S/MARs) are found in all eukaryotes. The pattern of distribution and genomic context of S/MARs is thought to be important for processes such as chromatin organization and modulation of gene expression. Despite the importance of such processes, much is unknown about the large-scale distribution and sequence content of S/ MARs in vivo. Here, we report the use of tiling microarrays to map 1358 S/MARs on Arabidopsis thaliana chromosome 4 (chr4). S/MARs occur throughout chr4, spaced much more closely than in the large plant and animal genomes that have been studied to date. Arabidopsis S/MARs can be divided into five clusters based on their association with other genomic features, suggesting a diversity of functions. While some Arabidopsis S/MARs may define structural domains, most occur near the transcription start sites of genes. Genes associated with these S/MARs have an increased probability of expression, which is particularly pronounced in the case of transcription factor genes. Analysis of sequence motifs and 6-mer enrichment patterns show that S/MARs are preferentially enriched in poly(dA:dT) tracts, sequences that resist nucleosome formation, and the majority of S/MARs contain at least one nucleosome-depleted region. This global view of S/MARs provides a framework to begin evaluating genome-scale models for S/MAR function. Contrast between DNA bound to nuclear scaffold/matrix and total genomic DNA in Arabidopsis Chr4 excluding the constitutive heterochromatin. Total of three biological replicates with two independent hybridizations on custom-designed NimbleGen high-density microarrays that include duplicate spots for each probe.