Nitrogen deprivation strongly affects Photosystem II but not phycoerythrin level in the divinyl-chlorophyll b-containing cyanobacterium Prochlorococcus marinus

AbstractEffects of nitrogen limitation on Photosystem II (PSII) activities and on phycoerythrin were studied in batch cultures of the marine oxyphotobacterium Prochlorococcus marinus. Dramatic decreases in photochemical quantum yields (FV/FM), the amplitude of thermoluminescence (TL) B-band, and the rate of QA reoxidation were observed within 12 h of growth in nitrogen-limited conditions. The decline in FV/FM paralleled changes in the TL B-band amplitude, indicative of losses in PSII activities and formation of non-functional PSII centers. These changes were accompanied by a continuous reduction in D1 protein content. In contrast, nitrogen deprivation did not cause any significant reduction in phycoerythrin content. Our results refute phycoerythrin as a nitrogen storage complex in Prochlorococcus. Regulation of phycoerythrin gene expression in Prochlorococcus is different from that in typical phycobilisome-containing cyanobacteria and eukaryotic algae investigated so far

Mutation of a single residue, β-glutamate-20, alters protein–lipid interactions of light harvesting complex II

It is well established that assembly of the peripheral antenna complex, LH2, is required for proper photosynthetic membrane biogenesis in the purple bacterium Rhodobacter sphaeroides. The underlying interactions are, as yet, not understood. Here we examined the relationship between the morphology of the photosynthetic membrane and the lipid–protein interactions at the LH2–lipid interface. The non-bilayer lipid, phosphatidylethanolamine, is shown to be highly enriched in the boundary lipid phase of LH2. Sequence alignments indicate a putative lipid binding site, which includes β-glutamate-20 and the adjacent carotenoid end group. Replacement of β-glutamate-20 with alanine results in significant reduction of phosphatidylethanolamine and concomitant raise in phosphatidylcholine in the boundary lipid phase of LH2 without altering the lipid composition of the bulk phase. The morphology of the LH2 housing membrane is, however, unaffected by the amino acid replacement. In contrast, simultaneous modification of glutamate-20 and exchange of the carotenoid sphaeroidenone with neurosporene results in significant enlargement of the vesicular membrane invaginations. These findings suggest that the LH2 complex, specifically β-glutamate-20 and the carotenoids' polar head group, contribute to the shaping of the photosynthetic membrane by specific interactions with surrounding lipid molecules

Planktonic Microbes in the Gulf of Maine Area

In the Gulf of Maine area (GoMA), as elsewhere in the ocean, the organisms of greatest numerical abundance are microbes. Viruses in GoMA are largely cyanophages and bacteriophages, including podoviruses which lack tails. There is also evidence of Mimivirus and Chlorovirus in the metagenome. Bacteria in GoMA comprise the dominant SAR11 phylotype cluster, and other abundant phylotypes such as SAR86-like cluster, SAR116-like cluster, Roseobacter, Rhodospirillaceae, Acidomicrobidae, Flavobacteriales, Cytophaga, and unclassified Alphaproteobacteria and Gammaproteobacteria clusters. Bacterial epibionts of the dinoflagellate Alexandrium fundyense include Rhodobacteraceae, Flavobacteriaceae, Cytophaga spp., Sulfitobacter spp., Sphingomonas spp., and unclassified Bacteroidetes. Phototrophic prokaryotes in GoMA include cyanobacteria that contain chlorophyll (mainly Synechococcus), aerobic anoxygenic phototrophs that contain bacteriochlorophyll, and bacteria that contain proteorhodopsin. Eukaryotic microalgae in GoMA include Bacillariophyceae, Dinophyceae, Prymnesiophyceae, Prasinophyceae, Trebouxiophyceae, Cryptophyceae, Dictyochophyceae, Chrysophyceae, Eustigmatophyceae, Pelagophyceae, Synurophyceae, and Xanthophyceae. There are no records of Bolidophyceae, Aurearenophyceae, Raphidophyceae, and Synchromophyceae in GoMA. In total, there are records for 665 names and 229 genera of microalgae. Heterotrophic eukaryotic protists in GoMA include Dinophyceae, Alveolata, Apicomplexa, amoeboid organisms, Labrynthulida, and heterotrophic marine stramenopiles (MAST). Ciliates include Strombidium, Lohmaniella, Tontonia, Strobilidium, Strombidinopsis and the mixotrophs Laboea strobila and Myrionecta rubrum (ex Mesodinium rubra). An inventory of selected microbial groups in each of 14 physiographic regions in GoMA is made by combining information on the depth-dependent variation of cell density and the depth-dependent variation of water volume. Across the entire GoMA, an estimate for the minimum abundance of cell-based microbes is 1.7×1025 organisms. By one account, this number of microbes implies a richness of 105 to 106 taxa in the entire water volume of GoMA. Morphological diversity in microplankton is well-described but the true extent of taxonomic diversity, especially in the femtoplankton, picoplankton and nanoplankton – whether autotrophic, heterotrophic, or mixotrophic, is unknown

Global Health - vermittle es mit einem Comic!

Aim: The topic of global health affects us all. In order to spread the word about this important medical field, a bilingual brochure containing medical comics on the subject was published at the Medical University of Vienna.Method: Medical comics are well established internationally, have a long history in the communication of medical information, and - under the umbrella of graphic medicine - are both popular and widely used. In the context of the exhibition project art-action-attitude/body, 6 panels were transformed into a 12-page brochure on the topic of global health in cooperation with an artist and a graphic designer.Results: The brochure was made available for free to visitors of the exhibition, published online, handed out at various fairs by the artist, and presented at an international conference.Summary: The collaboration with an artist and a graphic designer (Renate Mowlam, Bettina Jarosch) gave rise to a high-quality product that explains the subject matter clearly and in a way that is accessible to all, with the written word supported by images. In the brochure, 46 pictures shed light on the topics "health as a human right", "global health" (definition and examples), and "one health" (definition and examples). This enabled readers to quickly become informed about this complex subject, to contemplate it, and to reflect on their own behavior.Zielsetzung: Das Thema Global Health betrifft uns alle. Um dieses wichtige Forschungsfeld zu vermitteln, wurde an der Medizinischen Universität Wien anhand von Medical Comics eine Broschüre zu diesem Thema in zwei Sprachen herausgebracht.Methodik: Medical Comics sind international etabliert, mit langer Geschichte in der Kommunikation von medizinischen Informationen und finden - eingebettet in die Dachorganisation der Graphic Medicine - großen Zuspruch und Anwendung. Im Rahmen des Ausstellungsprojektes "Art-Action-Attitude/Körper" wurde aus 6 Panelen in Zusammenarbeit mit einer Künstlerin und einer Grafikerin zum Thema "Global Health" eine 12 Seiten umfassende Broschüre gestaltet. Ergebnisse: Die Broschüre wurde bei der Ausstellung gratis zur Mitnahme aufgelegt, online gestellt, von der Künstlerin auf diversen Messen ausgeteilt und auf einer internationalen Tagung vorgestellt.Resümee: Die Zusammenarbeit mit Professionistinnen (Renate Mowlam: Künstlerin; Bettina Jarosch: Grafikerin) hat sich in einem hochwertigen Produkt materialisiert, das Inhalte entsprechend klar und niederschwellig erklärt und bildlich unterstützt. Dabei wurden in 46 Bildern die Themen "Gesundheit als Menschenrecht", "Global Health" (Begriffserklärung und Beispiele) und "One Health" (Begriffserklärung und Beispiele) beleuchtet. So konnten sich Lesende rasch zu diesem komplexen Thema informieren, darüber nachdenken und das eigene Verhalten reflektieren