Study of the Effect of Phosphorus on Mineral Nutrition of Faba Bean « Vicia fabae L.»

Our study focuses on the study of the phosphorus efficiency on the mineral nutrition of a leguminous plant; to study this efficiency, we tested the effect of increasing doses of phosphorus on the mineral nutrition of faba bean and on the concentration of Nt (total nitrogen), Pi (available phosphorus), KE (exchangeable potassium), C (organic carbon), and the organic matter (OM) rate in the rhizospheric soil after harvest, as well as the concentration of N, P, K, Na, and Ca in the roots, stems, leaves, and seeds of faba bean. The faba bean crop was subjected to four phosphorus doses (P0?=?0 kg/ha; P1?=?70 kg/ha; P2?=?140 kg/ha; P3?=?210 kg/ha). The main results obtained showed that the concentration of the mineral elements in the different faba bean parts reacted differently to the phosphorus treatments. Regarding the dosage of nutrients in the different parts of the faba bean, the results obtained highlight that Pi deficiency in the soil does not only affect phosphate nutrition but can also affect the absorption of other mineral elements, a synergy is recorded between the K concentration in the roots and in the stems with the organic carbon in the soil, and an antagonism between K and Na in the different parts of the plant. All the results obtained in this work show that a phosphate fertilization for doses between 70 kg/ha and 140 kg/ha of P2O5 improves the microbial life of soil microorganisms.

     

Iron starvation leads to oxidative stress in Anabaena sp. strain PCC 7120

We establish here that iron deficiency causes oxidative stress in the cyanobacterium Anabaena sp. strain PCC 7120. Iron starvation leads to a significant increase in reactive oxygen species, whose effect can be abolished by treatment with the antioxidant tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl). Oxidative stress induced by iron starvation could be a common feature of photosynthetic bacteria.     

Multidrug-resistant phenotype and isolation of a Novel SHV- beta-Lactamase variant in a clinical isolate of Enterobacter cloacae

Background

ESBL-producing bacteria are a clinical problem in the management of diseases caused by these pathogens. Worldwide, systemic infections with BL enzymes are evolving by mutations from classical bla genes in an intensified manner and they continue to be transferred across species.

Results

E.cloacae BF1417 isolate and its transconjugants gave positive results with the DDST, suggesting the presence of ESBL. Sequence analysis revealed a bla_SHV-ESBL-type gene that differs from the gene encoding SHV-1 by five point mutations resulting in three amino acid substitutions in the coding region: C123R, I282T and L286P. This novel SHV-type enzyme was designated SHV-128. The conjugation tests and plasmid characterization showed that the bla_SHV-128 is located on a conjugative plasmid IncFII type. Expression studies demonstrated that the above mutations participated in drug resistance, hydrolysis of extended spectrum β-lactam and the change of the isoelectric point of the protein.

Conclusion

These findings underscore the diversity by which antibiotic resistance can arise and the evolutionary potential of the clinically important ESBL enzymes. In addition, this study highlights the need for systematic surveillance of ESBL-mediated resistance as well as in clinical areas and communities.     

Synthesis and Biological Activity of Chloroethyl Pyrimidine Nucleosides

The synthesis and biological activity of chloroethyl pyrimidine nucleosides is presented. One of these new nucleosides analogues significantly inhibited cell proliferation, migration and invasion as tested in vitro on the A431 vulvar epidermal carcinoma cell line.     

An Efficient DNA Extraction Method for Desert Calligonum Species

Genetic conservation programs in arid environments rely on molecular methods for diversity assessments. DNA-based molecular profiling will aid in conservation and protection of species from genetic erosion. Obtaining intact genomic DNA from Calligonum species, of sufficiently high-quality that is readily amplifiable using PCR, is challenging because of the presence of the exceptionally large amount of oxidized polyphenolic compounds, polysaccharides, and other secondary metabolites. The present method involves a modification of the available CTAB method employing higher concentrations of NaCl and CTAB, and incorporating PEG 6000 (1%) and glucose. The yield of DNA was 60-670 μg g(-1) of fresh tissue. The protocol has been tested with two species from the arid region. The DNA isolated was successfully amplified by two ITS primer pairs. PCR-RFLP analysis of the ITS1-5.8S-ITS2 region among and within Calligonum species followed by sequencing is under way.     

Teething with IKKalpha to make notches

Sharpe and colleagues unveil a crucial role for NF-kappaB activity in tooth development, and show that IKKalpha functions both within and independently from the NF-kappaB pathway during molar and incisor morphogenesis, respectively (in the February issue of Developmental Cell).     

Oxidative stress disrupts nitric oxide synthase activation in liver endothelial cells

Oxidative stress may mediate vascular disruption associated with a loss of endothelial nitric oxide synthase (eNOS) activity and a hypersensitivity to the constrictor effects of endothelin-1 (ET-1). We hypothesize that this is due, in part, to uncoupling of ET(B) receptors from eNOS activation. Thus, we tested whether oxidative stress (OS) affects liver vascular relaxation by reducing basal and ET-1-induced NO production. Primary sinusoidal endothelial cell cultures were pretreated with H(2)O(2) (25 microM) for 1 or 6 h before a 10-min ET-1 stimulation. OS resulted in a significant basal and ET-1-induced decrease in NO production. Acute OS increased the monomeric form of the inhibitory protein caveolin-1 (1.2 +/- 0.05 vs 0.9 +/- 0.02, p < 0.01) and increased the eNOS-caveolin association as determined by coimmunoprecipitation (1.24 +/- 0.04 vs 0.97 +/- 0.04, p < 0.05). ET-1 stimulation further exacerbated these effects. Subacute OS inhibited ET-1-induced eNOS phosphorylation of serine 1177 (activation residue) (1 +/- 0.07 vs 1.6 +/- 0.04, p < 0.05) and dephosphorylation of the inhibitory residue threonine 495 (1.5 +/- 0.08 vs 0.7 +/- 0.02, p < 0.01). Additionally subacute OS resulted in dissociation of eNOS from ET(B) (0.8 +/- 0.09 vs 1.2 +/- 0.06, p < 0.05). Our findings indicate that acute and subacute oxidative stress result in the inhibition of induced nitric oxide synthase activity through distinct mechanisms dependent on caveolin-1 inhibition, ET(B) dissociation, and eNOS phosphorylation.     

A large gene cluster encoding peptide synthetases and polyketide synthases is involved in production of siderophores and oxidative stress response in the cyanobacterium Anabaena sp. strain PCC 7120

Non-ribosomal peptide synthetases (NRPSs) and polyketide synthases (PKSs) are necessary for the production of a variety of secondary metabolites, such as siderophores involved in iron acquisition. In response to iron limitation, the cyanobacterium Anabaena sp. strain PCC 7120 synthesizes several siderophores. The chromosome of this organism contains a large gene cluster of 76 kb with 24 open-reading frames from all2658 to all2635, including those that encode seven NRPSs and two PKSs. The function of this gene cluster was unknown, and one possibility could be the synthesis of siderophores. These genes were indeed activated under conditions of iron limitation. One mutant, MDelta41-49, bearing a large deletion of 43.4 kb in this gene cluster, synthesized considerably less siderophores and contained less iron as compared with the wild type. Its growth rate was similar to the wild type in the presence of iron, but was reduced when iron became limiting. Two other mutants, MDelta44-45 and MDelta47-49, lacking either all2644 and all2645, or all2647, all2648 and all2649 respectively, produced more siderophores than MDelta41-49, but less than the wild type. These genes were also activated under oxidative stress conditions to which MDelta41-49 was highly sensitive, consistent with the importance of iron in oxidative stress response. We propose that this gene cluster is involved in the synthesis of siderophores in Anabaena sp. PCC 7120 and plays an important role in defence against oxidative stress.     

P2 receptors and immunity

Immune cells express receptors for extracellular nucleotides named P2 receptors. P2 receptors transduce signals delivered by nucleotides present in the extracellular environment. Accruing evidence shows that purinergic signalling has a profound effect on multiple immune cell responses such as T lymphocyte proliferation, chemotaxis, cytokine release, phagocytosis, Ag presentation and cytotoxicity. This makes P2 receptors an attractive target for the therapy of immuno-mediated disease and cancer.