Plastic responses lead to increased neurotoxin production in the diatom Pseudo-nitzschia under ocean warming and acidification.

Ocean warming (OW) and acidification (OA) are recognized as two major climatic conditions influencing phytoplankton growth and nutritional or toxin content. However, there is limited knowledge on the responses of harmful algal bloom species that produce toxins. Here, the study provides quantitative and mechanistic understanding of the acclimation and adaptation responses of the domoic acid (DA) producing diatom Pseudo-nitzschia multiseries to rising temperature and pCO2 using both a one-year in situ bulk culture experiment, and an 800-day laboratory acclimation experiment. Ocean warming showed larger selective effects on growth and DA metabolism than ocean acidification. In a bulk culture experiment, increasing temperature +4 °C above ambient seawater temperature significantly increased DA concentration by up to 11-fold. In laboratory when the long-term warming acclimated samples were assayed under low temperatures, changes in growth rates and DA concentrations indicated that P. multiseries did not adapt to elevated temperature, but could instead rapidly and reversibly acclimate to temperature shifts. However, the warming-acclimated lines showed evidence of adaptation to elevated temperatures in the transcriptome data. Here the core gene expression was not reversed when warming-acclimated lines were moved back to the low temperature environment, which suggested that P. multiseries cells might adapt to rising temperature over longer timescales. The distinct strategies of phenotypic plasticity to rising temperature and pCO2 demonstrate a strong acclimation capacity for this bloom-forming toxic diatom in the future ocean.

Enzyme-Free Colorimetric Method for Fast Detection of PIK3CA Gene Mutation by Praseodymia Nanorods.

The frequently mutated phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) gene is associated with multiple tumors and endocytosis of viruses. Identification of muted nucleotides at the hotspot can help in finding the susceptible people who are vulnerable to cancers and viruses. Herein, a simple enzyme-free colorimetric method is developed for the quick detection of PIK3CA gene mutations. The main mechanism lies in the dissimilar interactions between praseodymia nanorods and different nucleotides, as well as the underlying oxidase-mimicking characteristics of praseodymia. With rational designs of probes and processes, this method has great potential for expanded applications in the screening of mutations in other genes of interest.

The role of zinc in the adaptive evolution of polar phytoplankton.

Zinc is an essential trace metal for oceanic primary producers with the highest concentrations in polar oceans. However, its role in the biological functioning and adaptive evolution of polar phytoplankton remains enigmatic. Here, we have applied a combination of evolutionary genomics, quantitative proteomics, co-expression analyses and cellular physiology to suggest that model polar phytoplankton species have a higher demand for zinc because of elevated cellular levels of zinc-binding proteins. We propose that adaptive expansion of regulatory zinc-finger protein families, co-expanded and co-expressed zinc-binding proteins families involved in photosynthesis and growth in these microalgal species and their natural communities were identified to be responsible for the higher zinc demand. The expression of their encoding genes in eukaryotic phytoplankton metatranscriptomes from pole-to-pole was identified to correlate not only with dissolved zinc concentrations in the upper ocean but also with temperature, suggesting that environmental conditions of polar oceans are responsible for an increased demand of zinc. These results suggest that zinc plays an important role in supporting photosynthetic growth in eukaryotic polar phytoplankton and that this has been critical for algal colonization of low-temperature polar oceans.

Diversity and arsenic-tolerance potential of bacterial communities from soil and sediments along a gold tailing contamination gradient.

Gold tailings often release arsenic (As) contaminants into the surrounding environment. Microorganisms play an important role in the As cycle, whereas the effects of As on bacterial communities remain unclear. To reveal the effects of As on the diversity of bacterial communities and their As-tolerance potential, farmland soil and river sediment samples were collected at various distances from tailings in the Dandong area of northeastern China. The bacterial communities were analyzed using high-throughput sequencing of 16S rRNA genes. The membrane transport proteins ArsB and (or) ACR3 pump As(III) out of the cell to resist As toxicity. We studied the abundance and phylogeny of ArsB and ACR3 using PCR-based clone libraries and quantitative PCR. The bacterial community was divided into 10 phyla and 59 genera. The transformation from As(V) to As(III) was predominant, which was coupled with denitrification. Both ArsB and ACR3 likely evolved from different orders of Proteobacteria. The arsB gene seems to be more stable in bestowing bacteria with the capability to respond to the As concentration. Moreover, As with iron, manganese, and total organic carbon also influenced the clustering relationships of samples and bacterial distribution.

Composition and variation of sediment bacterial and nirS-harboring bacterial communities at representative sites of the Bohai Gulf coastal zone, China.

With rapid urbanization, anthropogenic activities are increasingly influencing the natural environment of the Bohai Bay. In this study, the composition and variation of bacterial and nirS-harboring bacterial communities in the coastal zone sediments of the Bohai Gulf were analyzed using PCR-based clone libraries. A total of 95 genera were detected in the bacterial communities, with Proteobacteria (72.1 %), Acidobacteria (10.5 %), Firmicutes (1.7 %), Bacteroidetes (1.4 %), Chloroflexi (0.7 %) and Planctomycetes (0.7 %) being the dominated phyla. The NirS sequences were divided into nine Clusters (A-I). Canonical correlation analysis showed that the bacterial or denitrifying communities were correlated with different environmental factors, such as total organic carbon, total nitrogen, ammonium, sulfate, etc. Furthermore, bacterial communities' composition and diversity are influenced by oil exploration, sewage discharge and other anthropogenic activities in the coastal area of the Bohai Sea. Thus, this study provided useful information on further research on regional or global environmental control and restore.

Differential gene expression in Ulva prolifera under low light and low temperature conditions.

The past several years witnessed the increasing global interest in the marine green macroalga Ulva prolifera as it is a key causative species of the massive green tides successively occurring in the Yellow Sea. Accurate localization of the 'seed' source is one of the principal scientific concerns to be solved before it is possible to manage these algal blooms. It has been suggested that somatic cells of Ulva prolifera which settled in cold benthic sediments might serve as one of the major propagule banks. To identify the molecular mechanisms underlying this hypothesis, PCR-based suppression subtractive hybridization was employed to analyze the differential gene expression of Ulva prolifera under low light and low temperature conditions (matching the cold benthic sediments conditions, 6 °C, 30 µmol photons m(-2) s(-1)). 137 ESTs representing 88 unigenes (80 singletons and 8 contigs) were detected as being over-expressed, whereas 109 unigenes (96 singletons and 13 contigs) in 130 ESTs were found to be down-regulated in this study. BLASTX analysis revealed that 65 % of the over-expressed and 59 % of the down-regulated genes did not belong to any documented functionally annotated or hypothetical proteins in the public database. However, analysis of the functional defined sequences displayed (1) an obvious sign of senescence, (2) enhancements of the photosynthesis system and the pentose phosphate pathway, (3) slow-down of activities in a wide range of processes including the DNA replication, the transcription, the translation, the glycolysis, the citrate cycle and the pyruvate metabolism in Ulva prolifera cells under low light and low temperature conditions. This work disclosed some basic information of the molecular mechanisms of Ulva prolifera cells under low light and low temperature conditions and provides useful clues for future studies on the "seed" source of the massive green tides.

Serine/threonine protein kinase SpkG is a candidate for high salt resistance in the unicellular cyanobacterium Synechocystis sp. PCC 6803.

BACKGROUND: Seven serine/threonine kinase genes have been predicted in unicellular cyanobacterium Synechocystis sp. PCC6803. SpkA and SpkB were shown to be required for cell motility and SpkE has no kinase activity. There is no report whether the other four STKs are involved in stress-mediated signaling in Synechocystis PCC6803. METHODOLOGY/PRINCIPAL FINDINGS: In this paper, we examined differential expression of the other four serine/threonine kinases, SpkC, SpkD, SpkF and SpkG, at seven different stress conditions. The transcriptional level was up-regulated of spkG and down-regulated of spkC under high salt stress condition. Two spk deletion mutants, ΔspkC and ΔspkG, were constructed and their growth characteristic were examined compared to the wild strain. The wild strain and ΔspkC mutant were not affected under high salt stress conditions. In contrast, growth of spkG mutant was completely impaired. To further confirm the function of spkG, we also examined the effect of mutation of spkG on the expression of salt stress-inducible genes. We compared genome-wide patterns of transcription between wild-type Synechocystis sp. PCC6803 and cells with a mutation in the SpkG with DNA microarray analysis. CONCLUSION: In this study, we first study the spkG gene as sensor of high salt signal. We consider that SpkG play essential roles in Synechocystis sp. for sensing the high salt signal directly, rather than mediating signals among other kinases. Our microarray experiment may help select relatively significant genes for further research on mechanisms of signal transduction of Synechocystis sp. PCC6803 under high salt stress.

Fatty acid biosynthesis in eukaryotic photosynthetic microalgae: identification of a microsomal delta 12 desaturase in Chlamydomonas reinhardtii.

Polyunsaturated fatty acids (PUFAs) are important components of infant and adult nutrition because they serve as structural elements of cell membranes. Fatty acid desaturases are responsible for the insertion of double bonds into pre-formed fatty acid chains in reactions that require oxygen and reducing equivalents. In this study, the genome-wide characterization of the fatty acid desaturases from seven eukaryotic photosynthetic microalgae was undertaken according to the conserved histidine-rich motifs and phylogenetic profiles. Analysis of these genomes provided insight into the origin and evolution of the pathway of fatty acid biosynthesis in eukaryotic plants. In addition, the candidate enzyme from Chlamydomonas reinhardtii with the highest similarity to the microsomal delta 12 desaturase of Chlorella vulgaris was isolated, and its function was verified by heterologous expression in yeast (Saccharomyces cerevisiae).

Vertical distribution of bacterial and archaeal communities along discrete layers of a deep-sea cold sediment sample at the East Pacific Rise (approximately 13 degrees N).

The community structure and vertical distribution of prokaryotes in a deep-sea (ca. 3,191 m) cold sediment sample (ca. 43 cm long) collected at the East Pacific Rise (EPR) approximately 13 degrees N were studied with 16SrDNA-based molecular analyses. Total community DNA was extracted from each of four discrete layers EPRDS-1, -2, -3 and -4 (from top to bottom) and 16S rDNA were amplified by PCR. Cluster analysis of DGGE profiles revealed that the bacterial communities shifted sharply between EPRDS-1 and EPRDS-2 in similarity coefficient at merely 49%. Twenty-three sequences retrieved from DGGE bands fell into 11 groups based on BLAST and bootstrap analysis. The dominant groups in the bacterial communities were Chloroflexi, Gamma proteobacteria, Actinobacterium and unidentified bacteria, with their corresponding percentages varying along discrete layers. Pairwise Fst (F-statistics) values between the archaeal clone libraries indicated that the archaeal communities changed distinctly between EPRDS-2 and EPRDS-3. Sequences from the archaeal libraries were divided to eight groups. Crenarchaea Marine Group I (MGI) was prevalent in EPRDS-1 at 83%, while Uncultured Crenarchaea group II B (UCII B) abounded in EPRDS-4 at 61%. Our results revealed that the vertically stratified distribution of prokaryotic communities might be in response to the geochemical settings and suggested that the sampling area was influenced by hydrothermalism. The copresence of members related to hydrothermalism and cold deep-sea environments in the microbial community indicated that the area might be a transitional region from hydrothermal vents to cold deep-sea sediments.