Inner workings: Diatom cell walls are outstanding examples of natural hybrid materials and exhibit interesting mechanical and optical properties. Removal of the biosilicates in the cell walls of T. pseudonana with NH4F proves that the cell walls contain an internal, organic network consisting of crosslinked chitin fibers as well as other organic components (see picture).

More decorative than wallpaper: Silica biomineralization in diatoms leads to intricate structures in the cell wall (see SEM image) and depends on structure‐directing templates formed by the electrostatically driven assembly of positively charged polyamine derivatives and polyanions. The title peptides are a family of biologically relevant polyanions present in diatom biosilica and composed mainly of serine phosphate and acidic amino acid residues.

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BackgroundShip engine emissions are important with regard to lung and cardiovascular diseases especially in coastal regions worldwide. Known cellular responses to combustion particles include oxidative stress and inflammatory signalling.ObjectivesTo provide a molecular link between the chemical and physical characteristics of ship emission particles and the cellular responses they elicit and to identify potentially harmful fractions in shipping emission aerosols.MethodsThrough an air-liquid interface exposure system, we exposed human lung cells under realistic in vitro conditions to exhaust fumes from a ship engine running on either common heavy fuel oil (HFO) or cleaner-burning diesel fuel (DF). Advanced chemical analyses of the exhaust aerosols were combined with transcriptional, proteomic and metabolomic profiling including isotope labelling methods to characterise the lung cell responses.ResultsThe HFO emissions contained high concentrations of toxic compounds such as metals and polycyclic aromatic hydrocarbon, and were higher in particle mass. These compounds were lower in DF emissions, which in turn had higher concentrations of elemental carbon (“soot”). Common cellular reactions included cellular stress responses and endocytosis. Reactions to HFO emissions were dominated by oxidative stress and inflammatory responses, whereas DF emissions induced generally a broader biological response than HFO emissions and affected essential cellular pathways such as energy metabolism, protein synthesis, and chromatin modification.ConclusionsDespite a lower content of known toxic compounds, combustion particles from the clean shipping fuel DF influenced several essential pathways of lung cell metabolism more strongly than particles from the unrefined fuel HFO. This might be attributable to a higher soot content in DF. Thus the role of diesel soot, which is a known carcinogen in acute air pollution-induced health effects should be further investigated. For the use of HFO and DF we recommend a reduction of carbonaceous soot in the ship emissions by implementation of filtration devices.

Diatoms are eukaryotic, unicellular algae encased within siliceous cell walls (frustules), which are precisely reproduced generation by generation. The production of this nanostructured silica is under genetic control and the isolation of specific gene products (the proteins silaffins, silacidins) guiding the biomineralization processes, and which are necessary to produce the frustules, has already been described. Under silicon starvation, the amount of silacidins present in the cell walls of Thalassiosira pseudonana increases relative to other proteins. Natsilacidins, the native and highly phosphorylated silacidins are enormously effective in silica precipitation whereas silacidin A', the nonphosphorylated form, is not. This indicates an important role for natsilacidins in the survival of diatoms under silicic acid depleted conditions.