Project description:Arctic Mesorhizobium strain N33 was isolated from nodules of the Oxytropis arctobia in Canada’s eastern Arctic. This symbiotic bacterium can grow from 0 to 30°C, is one of the best known cold-adapted rhizobia, and can fix nitrogen at ~10°C. Here, the key molecular mechanisms of cold adaptation were investigated by determining changes in transcript profiles when cells were treated under eight different temperature conditions, including both sustained and transient cold treatments compared with cells grown at room temperature.
2015-05-08 | GSE60710 | GEO
Project description:Whole genome sequences of bacteria isolated from a Malaysian tropical peat swamp forest
Project description:CCA-adding enzymes are highly specific RNA polymerases that synthesize and maintain the sequence CCA at the tRNA 3‘-end. Here, we investigated the impact of cold adaptation on the reactivity and specificity of CCA-adding enzymes from psychrophilic bacteria. A comparative study of the corresponding enzymes from closely related psychro-, meso-, and thermophilic Bacillales indicates that the cold-adapted enzymes show a considerable error rate during CCA synthesis, resulting in additional incorporations of C and A residues. It seems that the activity of psychrophilic CCA-adding enzymes is not only achieved at the expense of structural stability, reaction velocity and substrate affinity, but also results in a reduced polymerization fidelity.
Project description:Understanding how species adapt to changing environments is a major goal in evolutionary biology and can elucidate the impact of climate change. Climate imposes inevitable effects on the geographical distribution of insects as their body temperature primarily depends on the environment. The vinegar fly Drosophila ananassae expanded from its tropical ancestral range to more temperate regions, which requires adaptation to colder temperatures. Transcriptome and genome-wide association studies focusing on the ancestral-range population identified the targets of selection related to ionoregulatory tissues. However, how cosmopolitan D. ananassae adapted to colder environments, where low temperatures last longer, is still unknown. Here, we present a study on the effect of long-term cold exposure on D. ananassae, examining the gene expression variation in the whole body and the ionoregulatory tissues, namely the hindgut and the Malpighian tubule. To elucidate molecular mechanisms of cold adaptation during species expansion, we included cold-tolerant and cold-sensitive strains from the ancestral species range and cold-tolerant strains from the derived species range. We show that cold acclimation improves cold tolerance and results in differential expression of more than half of the transcriptome in the ionoregulatory tissues and the whole body. Notably, we provide complementary insight into molecular processes at four levels: strains, populations, phenotypes, and tissues. By determining the biochemical pathways of phenotypic plasticity underlying cold tolerance, our results enhance our understanding of how environmental changes affect thermal adaptation in natural populations.
Project description:RecBCD protein complex is an important player of DSB repair in bacteria and bacteria that cannot repair DNA double-stranded breaks (DSB) have a low viability. Whole genome sequencing analyses showed a deficit in specific sequences of the chromosome terminus region in recB mutant cells, suggesting terminus DNA degradation during growth. We studied here the phenomenon of terminus DNA loss by 42 whole genome sequencing and microscopy analyses of exponentially growing bacteria. We tested all processes known to take place in the chromosome terminus region for a putative role in DNA loss: replication fork termination, dimer resolution, resolution of catenated chromosomes, and translocation of the chromosome arms in daughter cells during septum formation. None of the mutations that affect these processes prevents the phenomenon. However, we observed that terminus DNA loss is abolished in cells that cannot divide. We propose that in cells defective for RecBCD-mediated DSB repair the terminus region of the chromosome remains in the way of the growing septum during cell division, then septum closure triggers chromosome breakage and, in turn, DNA degradation.
