Ditopic bis(oxazolines): Synthesis and structural studies of zinc(II), copper(II) and nickel(II) complexes

The synthesis, crystal structures, magnetic and spectroscopic properties of zinc(II), nickel(II) and copper(II) dinuclear complexes 2-4 of a novel dinucleating polyoxazoline ligand 1 are reported. X-ray analysis revealed that the three complexes are centrosymmetric dinuclear species with an overall S shape, the bisoxazoline moieties pointing toward the aromatic core of the molecule. Magnetic susceptibility measurements suggest that there is a very weak exchange interaction between the copper or nickel ions in complexes 3 and 4.     

Taxonomic and Functional Metagenomic Profiling of the Microbial Community in the Anoxic Sediment of a Sub-saline Shallow Lake (Laguna de Carrizo, Central Spain)

The phylogenetic and functional structure of the microbial community residing in a Ca(2+)-rich anoxic sediment of a sub-saline shallow lake (Laguna de Carrizo, initially operated as a gypsum (CaSO(4)?×?2 H(2)O) mine) was estimated by analyzing the diversity of 16S rRNA amplicons and a 3.1?Mb of consensus metagenome sequence. The lake has about half the salinity of seawater and possesses an unusual relative concentration of ions, with Ca(2+) and SO (4) (2-) being dominant. The 16S rRNA sequences revealed a diverse community with about 22% of the bacterial rRNAs being less than 94.5% similar to any rRNA currently deposited in GenBank. In addition to this, about 79% of the archaeal rRNA genes were mostly related to uncultured Euryarchaeota of the CCA47 group, which are often associated with marine and oxygen-depleted sites. Sequence analysis of assembled genes revealed that 23% of the open reading frames of the metagenome library had no hits in the database. Among annotated genes, functions related to (thio) sulfate and (thio) sulfonate-reduction and iron-oxidation, sulfur-oxidation, denitrification, synthrophism, and phototrophic sulfur metabolism were found as predominant. Phylogenetic and biochemical analyses indicate that the inherent physical-chemical characteristics of this habitat coupled with adaptation to anthropogenic activities have resulted in a highly efficient community for the assimilation of polysulfides, sulfoxides, and organosulfonates together with nitro-, nitrile-, and cyanide-substituted compounds. We discuss that the relevant microbial composition and metabolic capacities at Laguna de Carrizo, likely developed as an adaptation to thrive in the presence of moderate salinity conditions and potential toxic bio-molecules, in contrast with the properties of previously known anoxic sediments of shallow lakes.     

Induction of Prophages by Fluoroquinolones in Streptococcus pneumoniae: Implications for Emergence of Resistance in Genetically-Related Clones

Antibiotic resistance in Streptococcus pneumoniae has increased worldwide by the spread of a few clones. Fluoroquinolone resistance occurs mainly by alteration of their intracellular targets, the type II DNA topoisomerases, which is acquired either by point mutation or by recombination. Increase in fluoroquinolone-resistance may depend on the balance between antibiotic consumption and the cost that resistance imposes to bacterial fitness. In addition, pneumococcal prophages could play an important role. Prophage induction by fluoroquinolones was confirmed in 4 clinical isolates by using Southern blot hybridization. Clinical isolates (105 fluoroquinolone-resistant and 160 fluoroquinolone-susceptible) were tested for lysogeny by using a PCR assay and functional prophage carriage was studied by mitomycin C induction. Fluoroquinolone-resistant strains harbored fewer inducible prophages (17/43) than fluoroquinolone-susceptible strains (49/70) (P = 0.0018). In addition, isolates of clones associated with fluoroquinolone resistance [CC156 (3/25); CC63 (2/20), and CC81 (1/19)], had lower frequency of functional prophages than isolates of clones with low incidence of fluoroquinolone resistance [CC30 (4/21), CC230 (5/20), CC62 (9/21), and CC180 (21/30)]. Likewise, persistent strains from patients with chronic respiratory diseases subjected to fluoroquinolone treatment had a low frequency of inducible prophages (1/11). Development of ciprofloxacin resistance was tested with two isogenic strains, one lysogenic and the other non-lysogenic: emergence of resistance was only observed in the non-lysogenic strain. These results are compatible with the lysis of lysogenic isolates receiving fluoroquinolones before the development of resistance and explain the inverse relation between presence of inducible prophages and fluoroquinolone-resistance.     

Drought signal transduction in plants

Water deficit is one of the most common environmental limitations of crop productivity by affecting growth through alterations in metabolism and gene expression. The mechanisms involved in drought perception and signal transduction pathways are poorly understood. The participation of the plant hormone abscisic acid (ABA) has been well established. ABA levels increase when there are changes in the environment that result in cellular dehydration. Different approaches have been taken to understanding the molecular responses to desiccation and how ABA regulates gene expression. Recent efforts have identified particular topics of importance in the dissection of the signal transduction pathway which are summarized as follows: physiological approaches: identification of signalling molecules. Genetic approaches: the use of mutants, and Molecular approaches: promoter analysis.     

Role of peroxynitrite in programmed cell death induced in self-incompatible pollen

Reactive oxygen species and NO are involved in the signaling pathway of programmed cell death (PCD). Information concerning the role of these molecules in self-incompatible pollination is scarce especially in non-model species studied in vivo. We recently reported that in the olive tree, compatible and self-incompatible pollen have different levels of reactive oxygen and nitrogen species and that PCD is induced in self-incompatible pollen. Levels of O₂^.- and NO are higher in pollen after self-incompatible pollination than after compatible pollination. The presence of these reactive species was concomitant with the presence of peroxynitrite. Similar results were obtained on pollen-germination experiments both in vivo and in vitro. These data, together with observations made after treating pollinated flowers with scavengers, suggest that peroxynitrite plays a role in PCD induced after self-incompatible pollination and we propose here a model to describe the way in which it might work.     

Increases in mRNA concentrations of the alpha and beta subunits of prolyl 4-hydroxylase accompany increased gene expression of type IV collagen during differentiation of mouse F9 cells.

Mouse F9 teratocarcinoma stem cells differentiate in monolayer cultures in the presence of retinoic acid, dibutyryl cAMP, and isobutyl methylxanthine. This differentiation is associated with a marked increase in the synthesis rates and mRNA concentrations of basement membrane proteins such as type IV collagen. We report here that the differentiation also involves an increase of up to 50-fold in the concentrations of the mRNAs for the alpha and beta subunits of prolyl 4-hydroxylase, the enzyme required for the cotranslational and post-translational hydroxylation of proline residues in collagens. The time courses and magnitudes of increases in these two mRNA concentrations were similar to those observed in the same experiments for the mRNA of the alpha chain of type IV collagen. In the differentiated F9 cells the concentration of the alpha subunit mRNA was about 30% of the beta subunit mRNA concentration. Northern blot analyses indicated that the sizes of the alpha and beta subunit mRNAs in the differentiated mouse F9 cells are similar to those in human skin fibroblasts. The F9 cell differentiation system appears to provide a useful model for studies on the regulation of prolyl 4-hydroxylase synthesis.