10-Undecanhydroxamic acid, a hydroxamate derivative of the undecanoic acid, has strong antimicrobial activity through a mechanism that limits iron availability

Undecanoic acid (UDA) is a fatty acid with significant antimycotic activity. In this work we have synthesized 10-undecanhydroxamic acid, a hydroxamate derivative of the UDA, and tested its antimicrobial activity on different microorganisms. Our results demonstrate that this compound has higher efficacy than UDA against a variety of fungi and bacteria. Analysis of the intracellular concentration of protein involved in iron transport in Salmonella enterica serovar Typhimurium suggests that its antimicrobial effect actually relies on the ability to chelate iron ions, providing an efficient mechanism to interfere with microbial growth.     

Effect of oxygen and pentachlorophenol on the induction lag of photosynthesis in Chlamydomonas reinhardi

Following dark anaerobic incubation Chlamydomonas reinhardi exhibit a pronounced induction lag in photosynthesis; in contrast, dark aerobic incubation caused only a minimal induction lag. Addition of a low concentration of the uncoupler, pentachlorophenol (PCP), to respiring cells in darkness extended the induction period. Far red light preillumination partially overcame the induction lag resulting from dark anaerobic treatment or uncoupling with PCP in aerobic medium. The induction lag in photosynthesis is explained in terms of intracellular energy reserve and its effects on the level of phosphorylated intermediates of the Calvin cycle e.g., RuDP, in the dark. Further, evidence is presented which demonstrates that: (a) PCP, at concentrations below 10 μm, preferentially uncouples oxidative phosphorylation in vivo and (b) photophosphorylation, both in in vivo and in vitro, is much more resistant.     

Purification and characterization of an exo-polygalacturonase from the tomato vascular wilt pathogen Fusarium oxysporum f.sp. lycopersici

Abstract An exo-polygalacturonase (EC 3.2.1.15) was purified to apparent homogeneity from cultures of Fusarium oxysporum f.sp. lycopersici on synthetic medium supplemented with citrus pectin, using preparative isoelectric focusing. The enzyme, denominated PG2, had an apparent M _r of 74000 Da upon SDS-PAGE. The pI of the main PG2 isoform was 4.5, and pH and temperature optima were 5.0 and 55 °C, respectively. PG2 hydrolyzed polygalacturonic acid in an exo-manner, as demonstrated by anaysis of degradation products. The enzyme was N-glycosylated. The N-terminal amino acid sequence, L-A-F-N-V-P-S-K-P-P, has no identity to other known polygalacturonases.     

Quantitation of labile sulfide content and P700 photochemistry in spinach photosystem I particles

Treatment of spinach photosystem I particles with 2 or 4 M urea containing 5 mM ferricyanide produces a time-dependent conversion of labile sulfide to zero-valence sulfur in the membrane-bound iron-sulfur proteins. The integrity of the primary electron donor, P700, remains intact when measured as a chemical oxidized-minus-reduced difference spectrum. The effect on the light-induced oxidation of P700 is complex; the extent of the normally-fast P700 photooxidation correlates directly with the amount of labile sulfide remaining in the particle but a slow phase of photooxidation only becomes evident in increasingly depleted particles and shows no relationship with the amount of remaining labile sulfide. The data is taken as evidence for the participation of an iron-sulfur protein in the primary photochemistry of photosystem I in green plants.     

FbsC,a Novel Fibrinogen-binding Protein,Promotes Streptococcus agalactiae-Host Cell Interactions

Streptococcus agalactiae (group B Streptococcus or GBS) is a common cause of invasive infections in newborn infants and adults. The ability of GBS to bind human fibrinogen is of crucial importance in promoting colonization and invasion of host barriers. We characterized here a novel fibrinogen-binding protein of GBS, designated FbsC (Gbs0791), which is encoded by the prototype GBS strain NEM316. FbsC, which bears two bacterial immunoglobulin-like tandem repeat domains and a C-terminal cell wall-anchoring motif (LPXTG), was found to be covalently linked to the cell wall by the housekeeping sortase A. Studies using recombinant FbsC indicated that it binds fibrinogen in a dose-dependent and saturable manner, and with moderate affinity. Expression of FbsC was detected in all clinical GBS isolates, except those belonging to the hypervirulent lineage ST17. Deletion of fbsC decreases NEM316 abilities to adhere to and invade human epithelial and endothelial cells, and to form biofilm in vitro. Notably, bacterial adhesion to fibrinogen and fibrinogen binding to bacterial cells were abolished following fbsC deletion in NEM316. Moreover, the virulence of the fbsC deletion mutant and its ability to colonize the brain were impaired in murine models of infection. Finally, immunization with recombinant FbsC significantly protected mice from lethal GBS challenge. In conclusion, FbsC is a novel fibrinogen-binding protein expressed by most GBS isolates that functions as a virulence factor by promoting invasion of epithelial and endothelial barriers. In addition, the protein has significant immunoprotective activity and may be a useful component of an anti-GBS vaccine.     

Small,smaller… dendritic spine

Spines are highly motile protrusions emerging from the dendritic shafts of neurons. The dynamics of these post‐synaptic structures are ruled by actin filament turnover. However, our understanding of the mechanisms of actin polymerization in dendritic spines is quite ambiguous. A recent study by the Giannone laboratory (Chazeau et al, 2014 ) is now shedding some light on the peculiar features of actin polymerization in dendritic spines, which are distinct from the known canonical mechanisms.