Targeted-antibacterial-plasmids (TAPs) combining conjugation and CRISPR/Cas systems achieve strain-specific antibacterial activity

The global emergence of drug-resistant bacteria leads to the loss of efficacy of our antibiotics arsenal and severely limits the success of currently available treatments. Here, we developed an innovative strategy based on targeted-antibacterial-plasmids (TAPs) that use bacterial conjugation to deliver CRISPR/Cas systems exerting a strain-specific antibacterial activity. TAPs are highly versatile as they can be directed against any specific genomic or plasmid DNA using the custom algorithm (CSTB) that identifies appropriate targeting spacer sequences. We demonstrate the ability of TAPs to induce strain-selective killing by introducing lethal double strand breaks (DSBs) into the targeted genomes. TAPs directed against a plasmid-born carbapenem resistance gene efficiently resensitise the strain to the drug. This work represents an essential step toward the development of an alternative to antibiotic treatments, which could be used for in situ microbiota modification to eradicate targeted resistant and/or pathogenic bacteria without affecting other non-targeted bacterial species.     

Enzymes of arginine utilization and their formation in Aeromonas formicans NCIB 9232

In Aeromonas formicans two inducible catabolic pathways of L-arginine have been characterized. The arginine decarboxylase is induced by arginine which also induces the three enzymes of the arginine deiminase pathway but only in stress conditions such as a shift from aerobic growth conditions to very low oxygen tension. Addition of glucose to medium containing arginine leads to repression of the enzymes involved in the arginine deiminase pathway while exogenous cAMP prevents that repression of enzyme synthesis by glucose. This suggests that the induction of arginine deiminase pathway is regulated by carbon catabolite repression and the energetic state of the cell.     

Oligosaccharide structural specificity of the soluble agglutinin released from guinea pig colonic epithelial cells

Abstract Guinea pig colonic epithelial cells release a soluble lectin capable of agglutinating numerous strains of Shigella and Escherichia coli as well as other bacteria. Using pure oligosaccharides and glycopeptides with well-defined structures to inhibit the agglutination of Shigella flexneri 1b by the soluble intestinal lectin, we have been able to demonstrate that the latter recognises different structural types. Inhibition by human milk glucoprotein glycopeptides with biantennary glycans of the N -acetyllactosamine type was dependent on the simultaneous presence of unsubstituted terminal non-reducing galactose residues and of a fucose residue α-1,6-linked to the asparagine-conjugated N -acetylglucosamine residue. Unsubstituted terminal non-reducing galactose was also determinant for inhibition by human milk oligosaccharides. Finally oligosaccharides possessing the Man (α1–2) Man structure inhibited more effectively than those with a Man(α1–3)Man sequence. The fact that these different structural motifs were all inhibitory raises the problem of the possible existence of a multispecific lectin or of several different lectins in the guinea pig colonic mucosa mediating bacterial adherence.     

Sex-lethal in neurons controls female body growth in Drosophila

Sexual size dimorphism (SSD), a sex difference in body size, is widespread throughout the animal kingdom, raising the question of how sex influences existing growth regulatory pathways to bring about SSD. In insects, somatic sexual differentiation has long been considered to be controlled strictly cell-autonomously. Here, we discuss our surprising finding that in Drosophila larvae, the sex determination gene Sex-lethal (Sxl) functions in neurons to non-autonomously specify SSD. We found that Sxl is required in specific neuronal subsets to upregulate female body growth, including in the neurosecretory insulin producing cells, even though insulin-like peptides themselves appear not to be involved. SSD regulation by neuronal Sxl is also independent of its known splicing targets, transformer and msl-2, suggesting that it involves a new molecular mechanism. Interestingly, SSD control by neuronal Sxl is selective for larval, not imaginal tissue types, and operates in addition to cell-autonomous effects of Sxl and Tra, which are present in both larval and imaginal tissues. Overall, our findings add to a small but growing number of studies reporting non-autonomous, likely hormonal, control of sex differences in Drosophila, and suggest that the principles of sexual differentiation in insects and mammals may be more similar than previously thought.     

Bacterial filaments recover by successive and accelerated asymmetric divisions that allow rapid post-stress cell proliferation

Filamentation is a reversible morphological change triggered in response to various stresses that bacteria might encounter in the environment, during host infection or antibiotic treatments. Here we re-visit the dynamics of filament formation and recovery using a consistent framework based on live-cells microscopy. We compare the fate of filamentous Escherichia coli induced by cephalexin that inhibits cell division or by UV-induced DNA-damage that additionally perturbs chromosome segregation. We show that both filament types recover by successive and accelerated rounds of divisions that preferentially occur at the filaments' tip, thus resulting in the rapid production of multiple daughter cells with tightly regulated size. The DNA content, viability and further division of the daughter cells essentially depends on the coordination between chromosome segregation and division within the mother filament. Septum positioning at the filaments' tip depends on the Min system, while the nucleoid occlusion protein SlmA regulates the timing of division to prevent septum closure on unsegregated chromosomes. Our results not only recapitulate earlier conclusions but provide a higher level of detail regarding filaments division and the fate of the daughter cells. Together with previous reports, this work uncovers how filamentation recovery allows for a rapid cell proliferation after stress treatment.     

The acylphosphate present in chromaffin granule membrane preparations is not associated with the proton-pump

Chromaffin granule membranes were incubated in the presence of low ATP concentrations, at low temperature. A phosphorylated compound was rapidly formed which was stable in 10% trichloroacetic acid at 0 degree C. The lability of this compound in the presence of hydroxylamine or hot trichloroacetic acid indicated an acylphosphate, i.e., an ATPase phosphointermediate. Vanadate but not N-ethylmaleimide inhibited the formation of this derivative. Since the ATP-dependent generation of a transmembrane potential in chromaffin granule vesicles by the H+-pump was inhibited by N-ethylmaleimide but not by vanadate, the acylphosphate should not be associated with the H+-pump, i.e. ATPase I. We suggest that it is associated with ATPase II, an ATPase of unknown function present in chromaffin granule membrane preparations. This hypothesis is supported by the fact that ATPase II is vanadate sensitive and has a molecular mass of 140 kDa, properties similar to those of the phosphorylated intermediate.     

Activites proteolytiques et anti-trypsine des graines de Vigna unguiculata: Repartition et interaction

Data are given on distribution of caseolytic, BAPA-asic and anti-trypsin activities in albumins and globulins from embryos and cotyledons of Vigna seeds. Embryos are found to be richer in proteolytic enzymes than cotyledons. Trapping of anti-trypsin inhibitors solely enhances the albumin's caseolytic activities. Globulins do not show any BAPA-asic activity. The globulinic anti-trypsin inhibitors are similar on polyacrylamid gels (four fractions) whether the cotyledons or axes are used. The albuminic ones show one fraction more.