Biochemical insights into unique Bacteroidetes pore-forming toxins

The human gut microbiota is one of the densest and most complex microbial ecosystems on earth, harbouring hundreds of different species. This high microbial density and species diversity leads to fierce competition for nutrients and space, hence promoting bacterial antagonism. The Gram-negative Bacteroidetes are prominent long-term colonisers of the intestinal flora and represent on average 50% of all bacterial isolates within the human gut. They possess anti-inflammatory, immunomodulatory and metabolic properties and hence play a pivotal role in human health. To outmatch competitors, Bacteroidetes have evolved strategies to directly antagonize opponents through the production of antimicrobial molecules. Among these, the recently discovered Bacteroidales-secreted antimicrobial proteins (BSAPs) are of special interest as they form a novel class of bacterial pore-forming toxins (PFTs). PFTs are produced by a wide range of bacteia and possess the remarkable ability to transition from inert monomeric water-soluble proteins into integral membrane oligomers to form lytic pores. Uniquely, BSAPs possess a Membrane Attack Complex/Perforin (MACPF) domain usually found in eukaryotic pore-forming innate immunity proteins. Incubation of BSAP-sensitive cells with purified BSAPs causes uptake of the membrane-impermeable DNA dye propidium iodide, and co-culture experiments demonstrate that BSAP-producing strains kill sensitive cells in a BSAP-dependent manner. BSAPs are hence the first bacterial MACPF proteins with bactericidal activity. However, the underlying molecular mechanisms of lytic pore formation and receptor recognition remain cryptic. Here, we present first biochemical insights into BSAP receptor recognition and oligomerization, as well as preliminary structural data of a BSAP/receptor complex. Our findings indicate that highly variable BSAP C-terminal domains, located downstream of the MACPF domain, are the sole factor responsible for receptor recognition and binding. Structural characterization of a BSAP/receptor complex further dissects this interaction and how receptor binding affects positioning of the MACPF domain in respect to the membrane plane. Taken together, our data provide first biochemical insights into these novel and poorly characterized PFTs

An Athenian Decree Revisited

This paper focuses on an Athenian decree implementing a fundamental metrological reform at the end of the 2nd century BCE. This text has been known for a long time, since it was seen and copied by Michel Fourmont in Athens in 1729. The inscription is now lost, so that Fourmont’s sketch is our main source for this decree, together with a small fragment of a copy of the same decree found during the American excavations of the Agora in 1934. However, all current editions, including CIG I 123 (Boeckh, 1828), IG II 476 (Koehler, 1877), and IG II–III2 1013 (Kirchner, 1916), are not based on the draft sketch drawn by Michel Fourmont in Athens in 1729, but on a final version made by Claude-Louis Fourmont (Michel’s nephew) in Paris, probably between 1742 and 1746. Since the final version significantly differed from the original, it was necessary to re-edit the Athenian decree on the basis of the draft version (Supplément grec 854, fol. 79r–81r, no. 142), reject the supplements suggested by the previous editors, modify several restorations and interpretations, and revise the text structure. This paper also summarizes the main data provided by this decree about the Athenian metrological system during the late Hellenistic period, and challenges the communis opinio that the Athenians adopted the Roman standards at the end of the 2nd century BCE

Thin film transfer for the fabrication of multiple gate MOS transistors

A new approach in double gate devices processing based on the wafer bonding of a thin SOI film on pre-etched cavities is presented. In this context, wafer bonding parameters are analyzed. The effects of surface activation and annealing conditions are qualified, quantified and a viable solution is proposed

Storing energy in thin film solid oxide fuel cells through multi-functional anodes

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Combined in-situ curvature and resistivity monitoring to assess the morphological stability of solar concentrators in operando

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