Project description:Diverse studies including protemoics, genome-wide binding, and transcriptional profiling of the model halophile Halobacterium salinarum suggest that its putative histone protein acts not as a chromatin protein but a direct and indirect transcriptional regulator. Here, we characterise the putative histone (HstA) of another model halophile (Haloferax volcanii) with ChIP-Seq to understand its genome-wide binding, and compare it with binding patterns seen from histones, nucleoid-associated proteins, and transcription factors of Halobacterium salinarum, other archaea, and eukaryotes. Analysis of this data by visual inspection, start site occupancy profiles, DNA motif searching, and dinucleotide periodicity suggests that the binding mode of halophilic histones shares features with TFs, NAPs, and more typical archaeal/eukaryotic histones.
Project description:A high throughput proteomics approach was used to analyze and compare the proteome of two halophilic archaea (Haloferax volcanii and Natrialba magadii) during exponential and stationary growth.
Project description:Eukaryotic genomes typically consist of multiple (linear) chromosomes that are replicated from multiple origins. Several hypothetical scenarios have been proposed to account for the evolution of multi-origin/multi-chromosome genomes, which are encountered in modern eukaryotes and archaea. Here we report an example of the generation of a new chromosome in the halophilic archaeon Haloferax volcanii through one of these scenarios: acquisition of new replication origins and splitting of an ancestral chromosome into two replication-competent chromosomes. The multi-origin main chromosome has split into two genome elements via homologous recombination. The newly generated elements possess all the features of bona fide chromosomes. To our knowledge, the spontaneous generation of a new chromosome in prokaryotes without horizontal gene transfer has not been reported previously.
Project description:In order to understand extraceluular vesicle (EV) production in Euryarchaea, and in particular halophilic archaea, we used the model archaeal organism, Haloferax volcanii, to investigate the composition of EVs as well as their capacity to transfer their cargo to other organisms. EVs were isolated in tripclicates and purified with a density gradient. Both of two bands (upper and lower band) were isolated from the gradient and analysed seperately. Additionally, cellular membranes were isolated in triplicates and analysed for their protein content, to allow conclusions about proteins that are preferentially enclosed in EVs.
Project description:Oxidative stress adaptation strategies are important to cell function and are linked to cardiac, neurodegenerative disease and cancer. Representatives of the domain Archaea are used as model organisms based on their extreme tolerance to oxidants and close evolutionary relationship with eukaryotes. Study of the halophilic archaeon Haloferax volcanii reveals lysine acetylation to be associated with oxidative stress responses. The strong oxidant hypochlorite: i) stimulates an increase in lysine acetyltransferase HvPat2 to HvPat1 abundance ratios and ii) selects for lysine deacetylase sir2 mutants. Here we report the dynamic occupancy of the lysine acetylome of glycerol-grown H. volcanii as it shifts in profile in response to hypochlorite. These findings are revealed by the: 1) quantitative multiplex LC-MS/MS analysis of the SILAC-compatible parent and Δsir2 mutant strains and 2) label free LC-MS/MS analysis of H26 ‘wild type’ cells. The results show that lysine acetylation is associated with key biological processes including DNA topology, central metabolism, cobalamin biosynthesis and translation. Lysine acetylation targets are found conserved across species. Moreover, lysine residues modified by acetylation and ubiquitin-like sampylation are identified suggesting post-translational modification (PTM) crosstalk. Overall, the results of this study expand the current knowledge of lysine acetylation in Archaea, with the long-term goal to provide a balanced evolutionary perspective of PTM systems in living organisms.