The Phaeodactylum genome reveals the evolutionary history of diatom genomes.

Diatoms are photosynthetic secondary endosymbionts found throughout marine and freshwater environments, and are believed to be responsible for around one-fifth of the primary productivity on Earth. The genome sequence of the marine centric diatom Thalassiosira pseudonana was recently reported, revealing a wealth of information about diatom biology. Here we report the complete genome sequence of the pennate diatom Phaeodactylum tricornutum and compare it with that of T. pseudonana to clarify evolutionary origins, functional significance and ubiquity of these features throughout diatoms. In spite of the fact that the pennate and centric lineages have only been diverging for 90 million years, their genome structures are dramatically different and a substantial fraction of genes ( approximately 40%) are not shared by these representatives of the two lineages. Analysis of molecular divergence compared with yeasts and metazoans reveals rapid rates of gene diversification in diatoms. Contributing factors include selective gene family expansions, differential losses and gains of genes and introns, and differential mobilization of transposable elements. Most significantly, we document the presence of hundreds of genes from bacteria. More than 300 of these gene transfers are found in both diatoms, attesting to their ancient origins, and many are likely to provide novel possibilities for metabolite management and for perception of environmental signals. These findings go a long way towards explaining the incredible diversity and success of the diatoms in contemporary oceans.

Patulin and secondary metabolite production by marine-derived Penicillium strains.

Genus Penicillium represents an important fungal group regarding to its mycotoxin production. Secondary metabolomes of eight marine-derived strains belonging to subgenera Furcatum and Penicillium were investigated using dereplication by liquid chromatography (LC)-Diode Array Detector (DAD)-mass spectrometry (MS)/MS. Each strain was grown on six different culture media to enhance the number of observable metabolites. Thirty-two secondary metabolites were detected in crude extracts with twenty first observations for studied species. Patulin, a major mycotoxin, was classically detected in extracts of Penicillium expansum, and was also isolated from Penicillium antarcticum cultures, whose secondary metabolome is still to be done. These detections constituted the first descriptions of patulin in marine strains of Penicillium, highlighting the risk for shellfish and their consumers due to the presence of these fungi in shellfish farming areas. Patulin induced acute neurotoxicity on Diptera larvae, indicating the interest of this bioassay as an additional tool for detection of this major mycotoxin in crude extracts.

Size dependent bioaccumulation and ecotoxicity of gold nanoparticles in an endobenthic invertebrate: the Tellinid clam Scrobicularia plana.

Gold nanoparticles (AuNPs) have important technological applications resulting in an increased potential for release to the environment, and a greater possibility of toxicological effects. The marine bivalve Scrobicularia plana was exposed to AuNPs of size 5, 15 and 40 nm during a 16 d laboratory exposure at 100 µg Au L(-1). After exposure to AuNPs forming aggregates (>700 nm), the clams accumulated Au in their soft tissues. Biochemical (biomarkers) and behavioral (burrowing and feeding) responses were investigated. Au NPs were responsible of metallothionein induction (5, 40 nm), increased activities of catalase (15, 40 nm) and superoxide dismutase (40 nm) and of glutathione S-transferase by the three sizes of AuNPs indicating defense against oxidative stress. Exposure to AuNPs impaired burrowing behavior. However, it must be underlined that these effects were observed at a dose much higher than expected in the environment.