Antimicrobial and antiviral activities of an actinomycete (Streptomyces sp.) isolated from a Brazilian tropical forest soil

A promising producer of bioactive compounds isolated from a Brazilian tropical soil was tested for its range of antimicrobial activities. Strain 606, classified as Streptomyces sp., could not be identified up to species level, suggesting a possible new taxon. The supernatant and 10 extracts and fractions, obtained by extraction and chromatographic techniques, presented antimicrobial activity using antibiograms. The methanolic fraction was highly active against pathogenic bacteria, phytopathogenic fungi and the human pathogenic yeast Candida albicans. It also possessed high antiviral activity inhibiting the propagation of an acyclovir-resistant herpes simplex virus type 1 strain on HEp-2 cells at non-cytotoxic concentration. The strong cytotoxic effect suggests an antitumour action. This revised version was published online in August 2006 with corrections to the Cover Date.     

Intracellular Calcium Deficits in Drosophila Cholinergic Neurons Expressing Wild Type or FAD-Mutant Presenilin

Much of our current understanding about neurodegenerative diseases can be attributed to the study of inherited forms of these disorders. For example, mutations in the presenilin 1 and 2 genes have been linked to early onset familial forms of Alzheimer''s disease (FAD). Using the Drosophila central nervous system as a model we have investigated the role of presenilin in one of the earliest cellular defects associated with Alzheimer''s disease, intracellular calcium deregulation. We show that expression of either wild type or FAD-mutant presenilin in Drosophila CNS neurons has no impact on resting calcium levels but does give rise to deficits in intracellular calcium stores. Furthermore, we show that a loss-of-function mutation in calmodulin, a key regulator of intracellular calcium, can suppress presenilin-induced deficits in calcium stores. Our data support a model whereby presenilin plays a role in regulating intracellular calcium stores and demonstrate that Drosophila can be used to study the link between presenilin and calcium deregulation.     

Sex pheromones in maleMelittobia parasitic wasps: Female response to conspecific and congeneric males of 3 species

Presented a choice between conspecific males and 2 congeneric males, virgin females ofMelittobia australica andM. digitata chose conspecific males disproportionately more often, whereasM. femorata females distributed themselves evenly among the choices. Empty tubes, provided as the fourth choice in the test apparatus, were entered much less often than tubes containing live males. Females of all species chose “wrong” males about equally frequently. These observations suggest that even non-conspecific males possess some degree of attractiveness to virgin females. Chemicals in the sex pheromone of the males are presumed to be the source of the males' attractancy. The incomplete species specificity is interpreted in light of the life history of this genus, and it is suggested that specific recognition cues operate primarily after the sexes come together. Supported by a grant from Kagoshima Prefecture in Japan under the exchange program of faculty members between Kagoshima University and the University of Georgia.     

Sex differences in antipredator tail-waving displays of the diurnal yellow-headed gecko Gonatodes albogularis from tropical forests of Colombia

Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded. In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found no significant differences between males and females in flight-initiation distances and height above the substratum when they were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social function.     

GISHGenomic in situ hybridization reveals cryptic genetic differences between maize and its putative wild progenitor Zea mays subsp. parviglumis.

The aim of this paper is to test with genomic in situ hybridization the genomic affinities between maize and its putative progenitor Zea mays subsp. parviglumis. Blocking procedures were applied for the purpose of improving discrimination among chromosome regions. Unlabeled genomic DNA from Z. mays subsp. parviglumis as a blocking agent and labeled genomic DNA from maize were hybridized on maize chromosomes. On the other hand, mitotic metaphases from Z. mays subsp. parviglumis were blocked with unlabeled genomic DNA of maize and hybridized with labeled genomic DNA from Z. mays subsp. parviglumis. Both experiments showed that either maize or Z. mays subsp. parviglumis chromosomes have their own unique sequences. This means an unexpected degree of divergence if Z. mays subsp. parviglumis is the only progenitor of maize, a result that is discussed in relation to our previous genomic in situ hybridization observations and to the different scenarios proposed about the origin of maize.     

Isolation and biochemical characterization of Streptomyces clavuligerus mutants in the biosynthesis of clavulanic acid and cephamycin C

Summary Seven mutants of Streptomyces clavuligerus blocked in the biosynthesis of clavulanic acid, cephamycin C, or both antibiotics, have been isolated and characterized. Mutants nca1 and nca2 were unable to synthesize clavulanic acid but produced cephamycin C. Mutants nce1 and nce2 were completely blocked in cephamycin C production but formed clavulanic acid. A third group (mutants ncc1, ncc4 and ncc5) failed to produce both antibiotics. Arginase activity (forming ornithine) was very low in mutants ncc1 and ncc5. All the mutants blocked in clavulanic acid biosynthesis showed a normal ornithine--aminotransferase activity. Mutant ncc1, blocked in cephamycin biosynthesis, lacked completely lysine--aminotransferase (forming -aminoadipic acid) and isopenicillin N synthase. Two other mutants (nce2 and nce5) lacked isopenicillin N synthase. There was a good correlation between the isopenicillin N synthase and the lysine--aminotransferase activities of the nca mutants and the ability of those strains to produce cephamycin C. The condensing enzyme involved in the formation of the clavulanic acid nucleus appears to be different from the isopenicillin N synthase.Dedicated to Professor H.-J. Rehm on the occasion of his 60th birthday     

Calcium transport sensitive to ruthenium red in cytochrome oxidase vesicles reconstituted with mitochondrial proteins

We describe a calcium transport that is sensitive to ruthenium red in liposomes reconstituted with mitochondrial extracts. This system is able to build an internally negative membrane potential, which allows the electrogenic influx of Ca²⁺ and Sr²⁺. Proteins with molecular weights higher than 35 kDa were incorporated to the vesicles, and enhanced the accumulation of the cation in an energy-dependent fashion.     

Morphogenesis in leaf,hypocotyl and root explants of Digitalis thapsi L. cultured in vitro

The effects of the auxins 2,4-D, NAA and IAA either alone or in combination with kinetin or BA were investigated to assess the morphogenetic potential of leaf, root and hypocotyl explants of Digitalis thapsi. Calluses were obtained from the three explants in basal medium without the addition of growth regulators and in leaves, the calluses formed roots. Application of 2,4-D, NAA or BA increased callus formation. The presence of NAA induced root formation and that of BA induced shoot formation via callus interphase. Indole-3-acetic acid alone only induced the generation of roots in the hypocotyl callus. Kinetin was ineffective in all the explants tested. Combinations of NAA with kinetin or BA were more effective in inducing organogenesis in leaf explants. Optimum responses were obtained in hypocotyl and root explants by using IAA in combination with BA, the highest rate of shoot regeneration being observed in hypocotyl explants.Rooting of the differentiated shoots was readily achieved in media without growth regulators. Regenerated plantlets were transferred to soil and grew with a survival rate of 70%.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indoleacetic acid, Kin-kinetin - NAA naphthaleneacetic acid