Dynamic adoption of anergy by antigen-exhausted CD4+ T cells

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Effect of nitrogen,Rhizobium inoculation and simazine on yield and quality of Bengal gram (Cicer arietinum L.)

Summary A field experiment was conducted to study the effect of Rhizobium inoculation, nitrogen and simazine application, individually and in combination, on yield and quality of Bengal gram. Application of nitrogen and simazine, and seed inoculation with Rhizobium increased the grain yield significantly. The combined treatment of Rhizobium, simazine and nitrogen increased the grain yield to the extent of 70 per cent over control. Application of simazine increased the methionine content. re]19760609     

Speciation in sexually deceptive orchids: pollinator-driven selection maintains discrete odour phenotypes in hybridizing species

Ophrys orchids mimic the female sex pheromones of their pollinator species to attract males for pollination. Reproductive isolation in Ophrys is based on the selective attraction of only a single pollinator species. A change of floral odour can result in the attraction of a new pollinator species that acts as an isolation barrier towards other sympatrically occurring Ophrys species. Ophrys lupercalis, Ophrys bilunulata, and Ophrys fabrella grow sympatrically and bloom consecutively on Majorca and are pollinated by three species of Andrena. We investigated variation of phenotypic and genotypic flower traits, aiming to study the role of the floral odour for reproductive isolation and speciation. Using chemical and electrophysiology (gas chromatography coupled with an electroantennographic detector) methods, we show that the three Ophrys species use the same odour compounds for pollinator attraction, but in different proportions. A comparison of the floral odour bouquets in a multivariate analysis revealed a clear grouping of plants from the same species, although with an overlap between species. A comparison of the same plants using molecular markers gave a contrasting result. Although O. lupercalis and O. fabrella were genetically well separated, plants of O. bilunulata did not form a distinct group but were similar to either O. lupercalis or O. fabrella. Our data indicate gene flow and hybridization to occur between O. bilunulata and O. lupercalis as well as between O. bilunulata and O. fabrella. All plants of O. bilunulata, despite having different genotypes, showed a very similar floral odour. This reflects a strong selective pressure by the pollinating males. The overlap of genotypes of O. bilunulata and O. fabrella supports our hypothesis that O. fabrella diverged from O. bilunulata by scent variation and the attraction of a new pollinator species, Andrena fabrella. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98 , 439–451.     

Isolation of methanogens from Arabian sea sediments and their salt tolerance

Abstract Sea sediments in tropical regions have been less studied for methanogenesis and methanogens present therein. Three species of methanogens viz. Methanobacterium bryantii, Methanococcus voltae and Methanosarcina barkeri were isolated from Arabian sea sediments collected near the west coast of India. Maximum methane was formed by M. voltae at 3.0% (w/v) NaCl and other two methanogens at 0.06% (w/v) NaCl. M. bryantii and M. barkeri tolerated 2.5 and 3.0% (w/v) NaCl respectively due to which these methanogens must have survived in salt conditions of the sea sediments.     

Optimal pyoverdin-CPG composites for development of an optical biosensor to detect iron

Optical fluorescence-quenching-based biosensing cell is described and optimization of covalent binding of highly selective natural iron-chelating peptide secreted by bacteria is suggested. Pyoverdin biosynthesized by Pseudomonas monteilii and having 70% iron chelating activity was immobilized on amino alkylated controlled pore glass (CPG) and cross-linked with glutaraldehyde (2.5%, 28°C, 30 min). The pyoverdin-CPG immobilization was confirmed using fluorescence microscopic images (excitation range, 465–495 nm) for bright green fluorescence and by FTIR spectrum stretching at 3406.4 cm⁻¹ for amino group. The pyoverdin loading capacity of activated CPG matrix was 25 mg g⁻¹ of CPG and its rinsing analysis (leaking profile of the immobilized peptide vs. washing) detected negligible (2–3 μg) pyoverdin in the second wash.     

Bioactive compounds produced by cyanobacteria

Cyanobacteria produce a large number of compounds with varying bioactivities. Prominent among these are toxins: hepatotoxins such as microcystins and nodularins and neurotoxins such as anatoxins and saxitoxins. Cytotoxicity to tumor cells has been demonstrated for other cyanobacterial products, including 9-deazaadenosine, dolastatin 13 and analogs. A number of compounds in cyanobacteria are inhibitors of proteases — micropeptins, cyanopeptolins, oscillapeptin, microviridin, aeruginosins- and other enzymes, while still other compounds have no recognized biological activities. In general cyclic peptides and depsipeptides are the most common structural types, but a wide variety of other types are also found: linear peptides, guanidines, phosphonates, purines and macrolides. The close similarity or identity in structures between cyanobacterial products and compounds isolated from sponges, tunicates and other marine invertebrates suggests the latter compounds may be derived from dietary or symbiotic blue-green algae.