Proteome-wide analysis and diel proteomic profiling in the cyanobacterium Arthrospira platensis PCC 8005

The filamentous cyanobacteriumArthrospira platensishas a long history of use as a food supply and it has been used by the European Space Agency in the MELiSSA project, an artificial microecosystem which supports life during long-term manned space missions. This study assesses progress in the field of cyanobacterial shotgun proteomics and light/dark diurnal cycles by focusing onArthrospira platensis. Several fractionation workflows including gel-free and gel-based protein/peptide fractionation procedures were used and combined with LC-MS/MS analysis, enabling the overall identification of 1306 proteins, which represents 21% coverage of the theoretical proteome. A total of 30 proteins were found to be significantly differentially regulated under light/dark growth transition. Interestingly, most of the proteins showing differential abundance were related to photosynthesis, the Calvin cycle and translation processes. A novel aspect and major achievement of this work is the successful improvement of the cyanobacterial proteome coverage using a 3D LC-MS/MS approach, based on an immobilized metal affinity chromatography, a suitable tool that enabled us to eliminate the most abundant protein, the allophycocyanin. We also demonstrated that cell growth follows a light/dark cycle inA. platensis. This preliminary proteomic study has highlighted new characteristics of theArthrospira platensisproteome in terms of diurnal regulation

Sporulation, bacterial cell envelopes, and the origin of life

Electron cryotomography (ECT) enables the 3D reconstruction of intact cells in a near-native state. Images produced by ECT have led to the proposal that an ancient sporulation-like event gave rise to the second membrane in diderm bacteria. Tomograms of sporulating monoderm and diderm bacterial cells show how sporulation can lead to the generation of diderm cells. Tomograms of Gram-negative and Gram-positive cell walls and purified sacculi suggest that they are more closely related than previously thought and support the hypothesis that they share a common origin. Mapping the distribution of cell envelope architectures onto a recent phylogenetic tree of life indicates that the diderm cell plan, and therefore the sporulation-like event that gave rise to it, must be very ancient. One explanation for this model is that during the cataclysmic transitions of the early Earth, cellular evolution may have gone through a bottleneck in which only spores survived, which implies that the last bacterial common ancestor was a spore

The expression of a circadian rhythm in two strains of Chlamydomonas reinhardii in space

SIGLETIB Hannover: D.Dt.F. AC 1000(35,33) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

Mechanism of lipopolysaccharide-induced tumor necrosis: requirement for lipopolysaccharide-sensitive lymphoreticular cells.

Lipopolysaccharide (LPS) induces rapid necrosis of intradermal fibrosarcomas in mice. The mechanism(s) by which LPS produces tumor necrosis has been investigated using histocompatible LPS-sensitive (C3H/HeN) and LPS-resistant (C3H/HeJ) mouse strains. C3H/HeN- or C3H/HeJ-derived fibrosarcomas were necrotized by LPS when they were grafted onto C3H/HeN mice but were not affected when growing on C3H/HeJ mice, indicating that LPS does not act directly on the tumor itself. In contrast, lethally X-irradiated C3H/HeJ mice exhibit necrosis of their tumors when reconstituted with C3H/HeN bone marrow cells, whereas C3H/HeN mice no longer exert LPS-induced tumor necrosis after the adoptive transfer of C3H/HeJ bone marrow cells. These findings clearly indicate that LPS produces necrosis of tumors by activating host lymphoreticular cells