Project description:Allelopathy, or the release of compounds that inhibit competitors, is a form of interference competition that is common among bloom-forming phytoplankton. Allelopathy is hypothesized to play a role in bloom propagation and maintenance and is well established in the red tide dinoflagellate Karenia brevis. K. brevis typically suppresses competitor growth through unknown mechanisms over the course of many days. When we investigated the effects of allelopathy on the lipidomes of two competing phytoplankton, Asterionellopsis glacialis and Thalassiosira pseudonana using nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MS)- based metabolomics, we found that the lipidomes of both species were significantly altered, however A. glacialis maintained a more robust response whereas T. pseudonana saw significant alterations in fatty acid synthesis, cell membrane integrity, and a decrease in photosynthetic efficiency. Membrane- associated lipids were significantly suppressed for T. pseudonana exposed to allelopathy to the point of permeabilizing the cell membrane of living cells. The dominant mechanisms of K. brevis allelopathy appear to target lipid biosynthesis affecting multiple physiological pathways suggesting that exuded compounds have the ability to significantly alter competitor physiology and give K. brevis a competitive edge over sensitive species.
Project description:In order to unravel the role of regulation on transcript level in the central carbohydrate metabolism (CCM) of Thermoproteus tenax (glycolytic/gluconeogenic carbon switch), the focused DNA microarray was constructed by using ORFs supposed to be involved in the CCM pathways. Transcriptional profiling was performed comparing autotrophic growth on CO2/H2 versus heterotrophic growth on glucose.
Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into role of de novo transcription in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed RNA in Karenia brevis. These isolated fractions were then used for analysis of global de novo transcription by hybridization to a K. brevis microarray. As previous microarray studies indicated that transcripts for pentatricopeptide repeat (PPR) proteins rapidly increased in response to nutrient addition, we queried the newly synthesized RNA pools at 1 and 4 h following nitrate addition to N-depleted cultures. Transcriptome-wide there was little evidence of changes in the rate of de novo transcription during the first 4 h, relative to that in N-depleted cells, and no evidence for increased PPR protein transcription. These results lend support to the growing consensus of post-transcriptional control of gene expression in dinoflagellates.
Project description:Dinoflagellates possess many physiological processes that appear to be under post-transcriptional control. However, the extent to which their genes are regulated post-transcriptionally remains unresolved. To gain insight into the role of differential mRNA stability in dinoflagellates, we biosynthetically labeled RNA with 4-thiouracil to isolate newly transcribed and pre-existing RNA pools in Karenia brevis. These isolated fractions were then used for analysis of global mRNA stability by hybridization to a K. brevis microarray. Global K. brevis mRNA half-lives were calculated from the ratio of newly transcribed/pre-existing RNA for 7086 array features using the online software HALO (Half-life Organizer). Overall, mRNA half-lives were substantially longer than reported in other organisms studied at the global level, ranging from 42 minutes to greater than 3 days, with a median of 33 hours. Thirteen percent of messages showed a half-life of 3 days, demonstrating their stability throughtout the course of the cell cycle and divison. Consistent with well-documented trends observed in other organisms, housekeeping processes, including energy metabolism and transport, were significantly enriched in the most highly stable messages. Shorter-lived transcripts included a higher proportion of transcriptional regulation, stress response, and other response/regulatory processes.
2013-08-01 | GSE46174 | GEO
Project description:Bacterial Community of a Karenia longicanalis Bloom