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.     

Raman and infrared spectra of toxin gamma from the venom of the scorpion Tityus serrulatus

Toxin gamma is a basic, low-molecular-weight, neurotoxic protein, isolated from the venom of the Brazilian scorpion, Tityus serrulatus. Raman spectra (400-1800 cm-1 region) of this toxin in both the lyophilized state and in 0.1 M acetate buffer (pH 4.5) and the infrared spectrum (700-4000 cm-1 region) of a solid film were investigated. From the vibrational spectra, it can be concluded that the polypeptide backbone of toxin gamma consists of a mixture of the different secondary structures, with predominance of beta-sheet, followed by unordered structure and alpha-helix, with some evidence of beta-turn structures. The four disulfide bridges assume the gauche-gauche-gauche conformation of the CCSSCC fragments. The intensity ratio of the doublet at 853 and 828 cm-1 suggests that four out of the five tyrosine residues are exposed. The three tryptophan residues are exposed on the surface, and the single methionine residue assume the gauche-gauche conformation. Toxin gamma retains full activity in the pH 4.5-7.5 range, but is almost completely inactivated at pH 11.5.     

The growth rate variability ofChlorella vulgaris beijer. Clones grown after mutagen treatment under autotrophic or heterotrophic conditions on the surface of a solid medium

Populations of theChloretta vulgaris Beijeb. strain ?esnokov “V” clones (progenies of single cells) grown up from cells treated by chemical mutagens were cultivated on the surface of solid media. The differentiation of growth types according to their growth rates in the populations originating from the same sample of cells but growing under different conditions was compared. The strain studied exhibited much greater growth rate variability on the complete medium than on the minimal one. Short time changes of light regime during the cultivation for the purpose of inducing reparation processes in the mutagen damaged cells did not manifest themselves significantly in the composition of resulting clonal populations. The possibility of selection of growth types under conditions studied was considered.     

Effect of auto-oxidized phospholipids on oxidative enzyme assays based on tetrazolium salt reduction

The influence of auto-oxidized phospholipids on the reduction of the tetrazolium salt MTT coupled to the NAD+-dependent lactate dehydrogenase reaction was studied. The following results were obtained: (1) peroxidized phosphatidylcholine interfered in the time-course of the lactate dehydrogenase-mediated MTT reduction; (2) there was a time-dependent decrease in the hydroperoxide content of phosphatidylcholine vesicles during the incubation; (3) the diminution of phosphatidylcholine hydroperoxides required the presence of all the components of the system except MTT; (4) hydroperoxide diminution and MTT reduction were mediated by the superoxide radical O2-, since both processes were inhibited by superoxide dismutase; (5) EDTA inhibited the hydroperoxide decrease and abolished the interference of peroxidized phosphatidylcholine with MTT reduction. It was concluded that hydroperoxides compete with MTT for the electrons coming from substrate oxidation. The superoxide radical O2- and traces of some contaminating metal ion are involved in the process. This is a potential complication in the study of the effect of lipids on enzymatic activities assayed by the tetrazolium salt method.     

Ecology and biogeography of plant communities associated with the post Plio-Pleistocene relict Rhododendron ponticum subsp. baeticum in southern Spain

Aims Rhododendron ponticum L. is reputed to be a post Plio‐Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500‐m main transect in each site, along the stream or river course, in which we placed five 20‐m‐long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. ponticum individuals. Results Rhododendron ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.     

Long-wavelength fluorescence of tyrosine and tryptophan solutions

We report in this paper the presence of fluorescence bands of tryptophan and tyrosine solutions centered above 550 nm. This long-wavelength fluorescence is of much lower intensity, (0.4-2.7)%, than the UV fluorescence of these aromatic aminoacids. The basic characteristic of these fluorescence bands are: (a) tyrosine: lambda em = 600 nm with two excitation peaks centered at 453 nm and 550 nm (b) tryptophan: lambda em = 675 nm with two excitation peaks centered at 455 and 560 nm. It has been found that irradiation of tyrosine solutions with a potent UV lamp promotes an important increase of absorption at 310 nm and above 400 nm.     

Isolation from urine of two Serratia marcescens strains excreting a diffusible yellow pigment

Two bacterial strains excreting a yellow pigment were isolated from human urine and identified as Serratia marcescens. The pigment was produced in the late exponential and early stationary phases of growth. Minimal media supplemented with tyrosine, phenylalanine, 3,4-dihydroxyphenylacetate or tryptophan, as well as complex media, induced pigment production. UV-visible spectra of the extracted pigment had peaks characteristic of 2-hydroxy-5-carboxymethylmuconate semialdehyde, produced from meta-cleavage of 3,4-dihydroxyphenylacetate by the enzyme 3,4-dihydroxyphenylacetate 2,3-dioxygenase (EC 1.13.11.15). This enzyme was active when the bacteria were grown under conditions promoting pigment production. The kinetics and factors affecting pigment production are also reported.