Quantitative proteomics provides insight into the response of the marine dinoflagellate Prorocentrum donghaiense to changes in ambient phosphorus

Dinofl agellates are the major causative agents of harmful algal blooms in the global ocean and they usually form blooms under conditions of very low dissolved inorganic phosphorus(DIP).However,the mechanisms underpinning the dinofl agellate blooms remain unclear.Here,we quantitatively compared protein expression profi les of a marine dinofl agellate,Prorocentrum donghaiense,grown in inorganic P-replete,P-defi cient,and DIP-and dissolved organic phosphorus(DOP)-resupplied conditions by employing a Tandem Mass Tag(TMT)-based quantitative proteomic approach.Proteins involved in intracellular P reallocation,organic P,and non-P lipid utilization were up-regulated under the P-defi cient condition,while inorganic phosphate transporters varied insignifi cantly.In response to the P resupplementation,nitrogen metabolism,ribosome,porphyrin,and chlorophyll metabolism were up-regulated,while lysosome,and starch and sucrose metabolism were down-regulated.Notably,photosynthesis was up-regulated and secondary metabolism was down-regulated only in the DIP-resupplied cells,whereas amino acid metabolism and vitamin B6 metabolism were up-regulated in the DOP-resupplied cells,indicating diff erential response mechanisms of P.donghaiense to DIP or DOP resupplementation.Our results indicated that P.donghaiense initiated multiple strategies in response to an ambient inorganic P-defi ciency,and its efficient DOP assimilation by providing both P and carbon sources might be a key factor driving bloom formations of P.donghaiense in a low DIP environment.

Isolation and biological characteristics of aerobic marine magnetotactic bacterium YSC-1

Magnetotactic bacteria have become a hot spot of research in microbiology attracting inten-sive interest of researchers in multiple disciplinary fields. However, the studies were limited in few fas-tidious bacteria. The objective of this study aims at isolating new marine magnetic bacteria and better comprehension of magnetotactic bacteria. In this study, an aerobic magnetotactic bacterium YSC-1 was isolated from sediments in the Yellow Sea Cold Water Mass (YSCWM). In TEM, magnetic cells have one or several circular magnetosomes in diameter of 100nm, and consist of Fe and Co shown on energy dis-persive X-ray spectrum. The biological and physiological characteristics of this bacterium were also de-scribed. The colour of YSC-1 colony is white in small rod. The gram stain is negative. Results showed that Strain YSC-1 differs from microaerophile magnetotactic bacteria MS-1 and WD-1 in biology.

Compositional characteristics of sediment from Jiaozhou Bay in North China and the implication to the provenance

Rare earth elements(REEs)can be used to trace source materials and identify their provenances,because of significant conservation and immobility during chemical alteration processes after erosion of materials from the provenance.This study focused on the temporal variation of REEs for columnar sediments from the mouth of Jiaozhou Bay in North China to understand the potential controls for the geochemical variations of sediments.Through extraction experiments,we identified that the residual fraction is the main host for REEs compared with other fractions(i.e.,exchangeable and carbonate fraction,easily reducible oxides fraction,reducible oxides fraction,magnetite fraction).REE ratios(e.g.,La_(N)/Sm_(N)and La_(N)/Yb_(N);N:normalized by chondrite)lack correlations with grain size or the chemical index of alteration(CIA),which is correlated with major elements.All these indicate that these REE variations reflect the varying contribution of source materials from different provenances instead of grain size or chemical weathering effects.REE ratios(e.g.,La_(N)/Sm_(N)and La_(N)/Yb_(N))remain relatively constant until the depth of roughly 40 cm(equivalent to the year 1995),and show obvious changes beyond this depth.Compared REE characteristics of Jiaozhou Bay with those of neighboring rivers and bedrocks,the relative contributions of Dagu River-Jiaolai River,and Licun River may have been increased during the sedimentary processes,which could be caused by the construction of reservoir and related change of aquaculture(e.g.,rapid accumulation of organic materials).

Winter Phytoplankton Assemblages of Coastal Yellow Sea Connected to Jiaozhou Bay,China

The daily species variation of phytoplankton assemblage of coastal Yellow Sea connected to Jiaozhou Bay in the sea-water around the Xiaoqingdao Island was studied for the three months of winter, 2003. A total of 79 taxa from four phyla, Bacil-lariophyta (52 species), Pyrrophyta (25 species), Chrysophyta (1 species), and Cyanophyta (1species) were determined. In general, the most important groups were Bacillariophyta and Pyrrophyta on cell abundance and species richness. In January, the dominant species was mainly composed of cosmopolitan species such as Skeletonema costatum, then it changed to cosmopolitan species Tha-lassiosira nordenskiodii in February, and finally, it recovered to Skeletonema costatum again in March. Cell abundance ranged from 1.02 to 130.71×103 cells L-1with a single peak on 6th Feb., and the average abundance was 28.11 ± 26.01×103 cells L-1 (n = 90) during the winter time. The trends of Shannon-Weiner diversity index and Pielou’s evenness index were contrary to cell abundance, whereas the species diversity and evenness were the lowest in February. Temperature and salinity were closely correlated to phytoplankton species composition and cell abundance. According to the variations of temperature and salinity, species sequence was obvious at the studied site. This implies that the phytoplankton community of inner Jiaozhou Bay would be influenced heavily by the coastal Yel-low Sea phytoplankton assemblages.

Identification and characterization of endosymbiosis-related immune genes in deep-sea mussels Gigantidas platifrons

Deep-sea mussels of the subfamily Bathymodiolinae are common and numerically dominant species widely distributed in cold seeps and hydrothermal vents.During long-time evolution,deep-sea mussels have evolved to be well adapted to the local environment of cold seeps and hydrothermal vents by various ways,especially by establishing endosymbiosis with chemotrophic bacteria.However,biological processes underlying the establishment and maintenance of symbiosis between host mussels and symbionts are largely unclear.In the present study,Gigantidas platifrons genes possibly involved in the symbiosis with methane oxidation symbionts were identified and characterized by Lipopolysaccharide(LPS)pull-down and in situ hybridization.Five immune related proteins including Toll-like receptor 2(TLR2),integrin,vacuolar sorting protein(VSP),matrix metalloproteinase 1(MMP1),and leucine-rich repeat(LRR-1)were identified by LPS pull-down assay.These five proteins were all conserved in either molecular sequences or functional domains and known to be key molecules in host immune recognition,phagocytosis,and lysosome-mediated digestion.Furthermore,in situ hybridization of LRR-1,TLR2 and VSP genes was conducted to investigate their expression patterns in gill tissues of G.platifrons.Consequently,LRR-1,TLR2,and VSP genes were found expressed exclusively in the bacteriocytes of G.platifrons.Therefore,it was suggested that TLR2,integrin,VSP,MMP1,and LRR-1 might be crucial molecules in the symbiosis between G.platifrons and methane oxidation bacteria by participating in symbiosis-related immune processes.

Molecular insights into the circadian clock in marine diatoms

The circadian clock is a fundamental endogenous mechanism of adaptation that coordinates the physiology and behavior of most organisms with diel variations in the external environment to maintain temporal homeostasis.Diatoms are the major primary producers in the ocean.However,little is known about the circadian clock in marine diatoms compared with other organisms.Here,we investigated circadian clock genes,their expression patterns,and responses to environmental stimuli such as light,nitrogen and phosphorus in two marine diatoms,Skeletonema costatum and Phaeodactylum tricornutum,using a combination of q RT-PCR and bioinformatic analysis.We identified 17 and 18 circadian clock genes in P.tricornutum and S.costatum,respectively.Despite significant evolutionary differences,these genes were similar to those of the higher plant Arabidopsis.We also established a molecular model for the marine diatom circadian clock comprising an input pathway,core oscillator,output pathway,and valve effector.Notably,the expression patterns of core clock genes(circadian clock associated 1(CCA1),late elongated hypocotyl(LHY)and timing of cab 1(TOC1))in both species differed from those of terrestrial plants.Furthermore,the expression of these genes was influenced by variations in ambient light,nitrogen and phosphorus availability.Although marine diatoms and higher plants share common circadian clock components,their clock genes have diverged throughout evolution,likely as a result of adapting to contrasting environments.

Reductive degradation of chloramphenicol by Geobacter metallireducens

Geobacter metallireducens is known to be capable of removing nitroaromatic compounds via an oxidation mode. However, little attention has been paid to investigate the reductive removal of chlorinated nitroaromatic compounds by G. metallireducens. In this study, G. metallireducens was used to reduce chloramphenicol(CAP), a typical chlorinated nitroaromatic antibiotic. Cyclic voltammograms and chronoamperometry highlighted a higher peak current for CAP reduction by G. metallireducens compared to the control without bacteria. G. metallireducens efficiently reduced CAP(20 mg/L) with acetate as the sole electron donor, and the removal efficiency reached(97.6±4.9)% within 6 d. Aromatic amine(AMCl2), AMCl(dechlorinated AMCl2) and AM(dechlorinated AMCl) were identified as reduction products by liquid chromatography-mass spectrometry. However, the removal efficiency declined to(25.0±3.6)% when the CAP dosage increased to 80 mg/L. Transcriptomic analysis indicated the significant upregulation of genes related to electron transfer, such as pilus assembly protein gene(2.8 folds), NADH-quinone oxidoreductase subunit K2 gene(4.5 folds) and many c-type cytochrome genes such as cytochrome c biogenesis protein Res B(Gmet 2901, 4.6 folds), cytochrome c(Gmet 0335, 4.4 folds) and cytochrome c7(Gmet 2902, 3.4 folds). Furthermore, a gene related to chlorinated contaminant removal(Gmet 1046, 5.4 folds) was also upregulated, possibly resulting in enhanced CAP reduction. This work deepened our knowledge of the bioremediation ability of G. metallireducens with respect to environmental contaminants and provided a potential strategy to treat antibiotics with electrochemically active bacteria.