A metagenomic library of 10,121 clones, generated from bacteria inhabiting a pasture soil from France, was screened for the presence of fosmids conferring either N-acylhomoserine lactone (NAHL) synthesis or NAHL degradation ability upon their Escherichia coli host. No clone producing NAHLs was identified whereas one, containing a 31 972 bp insert in fosmid p2H8, allowed NAHL degradation. This led to the cloning and identification of a gene, qlcA, encoding an NAHL-lactonase activity, as judged by lactone-ring closure and HPLC/MS analyses of NAHL degradation products. The qlcA gene efficiently quenched quorum-sensing regulated pathogenic functions when expressed in Pectobacterium carotovorum. The QlcA peptide belongs to the family of zinc-dependent metallohydrolases and appears to be distantly related to other NAHL-lactonases discovered in Agrobacterium, Bacillus, Photorhabdus and Rhizobium. In-silico analysis of the metagenomic insert revealed the occurrence of 20 orf, with a constant GC% and codon usage, suggesting a unique bacterial origin. Nine out of these 20 orf were homologous to genes encoding biosynthesis of arginine; they were clustered with an unusual succession argFJADBCRGH. The fosmid p2H8 is able to complement the argA, argB and argC mutants in E. coli. Phylogenetic analysis showed that 9 orf out of 20 were related to sequences from members of the Acidobacteria, supporting the hypothesis that the analysed insert might be originated from an organism related to this phylum.
Tomato (Lycopersicon esculentum Mill.) is an important commercial vegetable of the world. Tomato cultivars cultivated in Pakistan have low level of genetic resistance to Alternaria leaf blight disease. Farmers, in pursuance of high yield are inclined to cultivate some varieties which may be less resistant to the disease and rely on fungicide applications for the control of Alternaria solani, the casual organism of Alternaria blight of tomato. Five tomato varieties (Litah545, Litah514, Eurica, Ti-166 and Astra) were sown in five replications with one standard check in tunnel. Different doses of mancozeb (4 g/L, 8 g/L, 12 g/L and 16 g/L of water) were applied after 7 days intervals. Disease data was recorded after ten days interval from flowering stage to onward. Average yield of each variety was calculated after ten pickings. All fungicide doses reduce the disease severity as compared to untreated check. The highest reduction in the disease was achieved by applying mancozeb 12 g/L of water at an interval of 7, 14, 21 and 28 days. The yield of Litah545 and Litah514 give higher yield as compared to Eurica, Ti-166 and Astra. Overall results revealed that weekly sprays of mancozeb at 12 g/L of water were cost effective and eco-friendly for the management of Alternaria blight of tomato.
BackgroundCoumarin and its derivatives are biologically very active. It was found that the enhanced activities are dependent on the coumarin nucleus. Biological significance of these compounds include anti-bacterial, anti-thrombotic and vasodilatory, anti-mutagenic, lipoxygenase and cyclooxygenase inhibition, scavenging of reactive oxygen species, and anti-tumourigenic. Our interest in medicinal chemistry of dicoumarol compounds have been developed by keeping in view the importance of coumarins along with its derivatives in medicinal chemistry. All the synthesized compounds were fully characterized by spectroscopic and analytical techniques and were screened for antimicrobial and U2OS bone cancer activities.Results4-hydroxycoumarin was derivatized by condensing with different aldehydes yielding the dicoumarol and translactonized products. Elemental analyses, ESI(+,−) MS, 1H and 13C{1H}-NMR, infrared spectroscopy and conductance studies were used to characterize the synthesized compounds which revealed the dicoumarol and dichromone structures for the compounds. The compounds were screened against U2OS cancerous cells and pathogenic micro organisms. The compounds with intermolecular H-bonding were found more active revealing a possible relationship among hydrogen bonding, cytotoxicity and antimicrobial activities.ConclusionCoumarin based drugs can be designed for the possible treatment of U2OS leukemia.
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