The Regulatory Network of Natural Competence and Transformation of Vibrio cholerae

The human pathogen Vibrio cholerae is an aquatic bacterium frequently encountered in rivers, lakes, estuaries, and coastal regions. Within these environmental reservoirs, the bacterium is often found associated with zooplankton and more specifically with their chitinous exoskeleton. Upon growth on such chitinous surfaces, V. cholerae initiates a developmental program termed “natural competence for genetic transformation.” Natural competence for transformation is a mode of horizontal gene transfer in bacteria and contributes to the maintenance and evolution of bacterial genomes. In this study, we investigated competence gene expression within this organism at the single cell level. We provide evidence that under homogeneous inducing conditions the majority of the cells express competence genes. A more heterogeneous expression pattern was observable on chitin surfaces. We hypothesize that this was the case due to the heterogeneity around the chitin surface, which might vary extensively with respect to chitin degradation products and autoinducers; these molecules contribute to competence induction based on carbon catabolite repression and quorum-sensing pathways, respectively. Therefore, we investigated the contribution of these two signaling pathways to natural competence in detail using natural transformation assays, transcriptional reporter fusions, quantitative RT–PCR, and immunological detection of protein levels using Western blot analysis. The results illustrate that all tested competence genes are dependent on the transformation regulator TfoX. Furthermore, intracellular cAMP levels play a major role in natural transformation. Finally, we demonstrate that only a minority of genes involved in natural transformation are regulated in a quorum-sensing-dependent manner and that these genes determine the fate of the surrounding DNA. We conclude with a model of the regulatory circuit of chitin-induced natural competence in V. cholerae

Glacial Isostatic Adjustment (GIA) in Greenland: a Review

Using the most recently published regional and global deglaciation histories we provide updated estimates of the Glacial Isostatic Adjustment (GIA) component of present day uplift at a suite of GPS sites in Greenland. The GIA of the solid Earth beneath Greenland contributes -6 to +10 Gt/yr to the present day mass trends observed by the Gravity Recovery and Climate Experiment (GRACE), representing <5% contribution to the observed mass trends over the last decade. Although the contribution of GIA to GRACE estimates of mass imbalance is insignificant for Greenland as a whole, differences between deglacial models reviewed here and their assumed viscoelastic Earth structures result in significantly different estimates of regional patterns and magnitudes of GIA. This means that for some areas of Greenland (e.g. the north-west, south- and north-east) the use of GNSS to estimate elastic uplift patterns is more affected by the choice of GIA correction applied

Ornamental expression of red fluorescent protein in transgenic founders of white skirt tetra (Gymnocorymbus ternetzi)

10.1007/s10126-008-9094-9Marine Biotechnology105497-501MABI

A greener world: The revolution in plant bioimaging

The exploitation of fluorescent proteins has heralded a new age in the in vivo analysis of subcellular events, and has overcome many of the limitations that are associated with the investigation of cellular and molecular processes in plant cells. Recently, there have been many exciting applications of green fluorescent protein and its spectral derivatives in the study of plant cells