40 research outputs found
Identification and Characterization of Microcin S, a New Antibacterial Peptide Produced by Probiotic Escherichia coli G3/10
Escherichia coli G3/10 is a component of the probiotic drug Symbioflor 2. In an in vitro assay with human intestinal epithelial cells, E. coli G3/10 is capable of suppressing adherence of enteropathogenic E. coli E2348/69. In this study, we demonstrate that a completely novel class II microcin, produced by probiotic E. coli G3/10, is responsible for this behavior. We named this antibacterial peptide microcin S (MccS). Microcin S is coded on a 50.6 kb megaplasmid of E. coli G3/10, which we have completely sequenced and annotated. The microcin S operon is about 4.7 kb in size and is comprised of four genes. Subcloning of the genes and gene fragments followed by gene expression experiments enabled us to functionally characterize all members of this operon, and to clearly identify the nucleotide sequences encoding the microcin itself (mcsS), its transport apparatus and the gene mcsI conferring self immunity against microcin S. Overexpression of cloned mcsI antagonizes MccS activity, thus protecting indicator strain E. coli E2348/69 in the in vitro adherence assay. Moreover, growth of E. coli transformed with a plasmid containing mcsS under control of an araC PBAD activator-promoter is inhibited upon mcsS induction. Our data provide further mechanistic insight into the probiotic behavior of E. coli G3/10
Shark fossil diversity (Squalomorphii, Squatinomorphii, and Galeomorphii) from the Langhian of Brielas (Lower Tagus Basin, Portugal)
The fossiliferous marine Miocene sediments of the Lower Tagus Basin (Portugal) present
a great diversity of Chondrichthyes forms. The current study focuses on the fossil
sharks from the Langhian Vc unit of the Brielas section, located in the Setúbal
Peninsula. A total of 384 isolated fossil teeth were analysed and ascribed to 17 species from the Orders Hexanchiformes, Squaliformes, Squatiniformes, Lamniformes,
and Carcharhiniformes. Centrophorus granulosus and Iago angustidens are described
for the first time in Portuguese sediments, whereas Pachyscyllium dachiardii and
Rhizoprionodon ficheuri represent only their second reported occurrence. Galeorhinus
goncalvesi was already known from the Portuguese uppermost Miocene (Alvalade
Basin), but it is now recognized in older sediments. Furthermore, the new material
seems to include the first reported occurrence of Hexanchus cf. agassizi in Miocene
sediments. As a whole, these new findings support the previous palaeoenvironment
characterization of a warm infralittoral setting gradually deepening to a circalittoral
one, where seasonal upwelling phenomena could have occurred
A Novel Protein Kinase-Like Domain in a Selenoprotein, Widespread in the Tree of Life
Selenoproteins serve important functions in many organisms, usually providing essential oxidoreductase enzymatic activity, often for defense against toxic xenobiotic substances. Most eukaryotic genomes possess a small number of these proteins, usually not more than 20. Selenoproteins belong to various structural classes, often related to oxidoreductase function, yet a few of them are completely uncharacterised
Efficient prism modeling for arbitrary-shape antennas printed on finite-size dielectric substrate in EFIE analysis
International audienceThe volume equivalence principle is used for 3-D arbitrary geometry analysis, printed on a finite-size dielectric slab. Simple basis functions associated with triangular prism elements are studied for substrate modeling. The results of convergence on input impedance are presented. Experiments on printed monopoles confirm the theoretical results, on a wide band of frequency, for different geometries and permittivity value