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.     

Isolation of fungi from bats of the Amazon basin

A total of 2,886 bats captured in the Amazon Basin of Brazil were processed for the isolation of fungi. From the livers, spleens, and lungs of 155 bats (5.4%), 186 fungal isolates of the genera Candida (123 isolates), Trichosporon (26 isolates), Torulopsis (25 isolates), Kluyveromyces (11 isolates), and Geotrichum (1 isolate) were recovered. Seven known pathogenic species were present: Candida parapsilosis, C. guilliermondii, C. albicans, C. stellatoidea, C. pseudotropicalis, Trichosporon beigelii, and Torulopsis glabrata. Twenty-three culture-positive bats showed identical fungal colonization in multiple organs or mixed colonization in a single organ. The fungal isolation rates for individual bat species varied from 1 fungus per 87 bats to 3 fungi per 13 bats, and the mycoflora diversity for members of an individual fungus-bearing bat species varied from 16 fungi per 40 bats to 7 fungi per 6 bats. Of the 38 fungal species isolated, 36 had not been previously described as in vivo bat isolates. Of the 27 culture-positive bat species, 21 had not been previously described as mammalian hosts for medically or nonmedically important fungi.     

Extracellular ATP and adenosine modulate tumor necrosis factor-induced lysis of L929 cells in the presence of actinomycin D

Extracellular ATP in concentrations of 0.5 to 2.5 mM modulates TNF-induced cytolysis of L929 cells in the presence of actinomycin D. When present throughout the entire assay period, it inhibits the TNF-induced cytolysis. ADP was less active whereas AMP and GTP were nonreactive. However, inhibition was also achieved by adenosine that was nearly as active as ATP. Yet, the inhibitory effect of ATP was not due to hydrolysis by ectoenzymes to form adenosine. Thus, the nonhydrolyzable ATP analogue adenyl(beta-gamma-methylendiphosphate) was equally effective in inhibiting TNF-induced cytolysis. Moreover, no conversion of ATP into adenosine was observed during the entire assay period. However, inhibition no longer occurred when the TNF and ATP containing medium was removed after 5 h and replaced by a fresh medium containing TNF and no ATP. We now observed substantial enhancement of the TNF-induced cytolysis by ATP. Finally, treatment with N6-(R-phenylisopropyl)adenosine or with aminophylline, which are thought to downregulate adenosine receptors and to prevent binding of ligands to adenosine receptors, respectively, abolishes adenosine and ATP-mediated inhibition. Again, substantial enhancement of the TNF-induced cytolysis was observed by ATP and only a minor effect by adenosine. The results together suggest that ATP interacts with purinoceptors on the plasma membrane and is capable to enhance and inhibit TNF-induced cytolysis under appropriate conditions. The outcome of the ATP-induced modulation may be influenced by adenosine receptors.     

Raman spectroscopic investigation of the interaction of gramicidin A with dipalmitoyl phosphatidylcholine liposomes.

The interaction of gramicidin A with dipalmitoyl phosphatidylcholine liposomes is investigated by Laser-Raman spectroscopy. As revealed by the methylene C-H stretching mode the phase transition of the hydrocarbon chains near 40 degree C is eliminated in the presence of gramicidin A. Liposomes prepared from a mixture of lecithin and cholesterol seem to be unaffected by gramicidin A and show only the normal broadened phase transition.