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.     

The role of humans in the diversification of a threatened island raptor

Background  

Anthropogenic habitat modifications have led to the extinction of many species and have favoured the expansion of others. Nonetheless, the possible role of humans as a diversifying force in vertebrate evolution has rarely been considered, especially for species with long generation times. We examine the influence that humans have had on the colonization and phenotypic and genetic differentiation of an insular population of a long-lived raptor species, the Egyptian vulture (Neophron percnopterus).     

Colonization and extinction of land planarians (Platyhelminthes,Tricladida) in a Brazilian Atlantic Forest regrowth remnant

Long-term assessments of species assemblages are valuable tools for detecting species ecological preferences and their dispersal tracks, as well as for assessing the possible effects of alien species on native communities. Here we report a 50-year-long study on population dynamics of the four species of land flatworms (Platyhelminthes, Tricladida, Terricola) that have colonized or become extinct in a 70-year-old Atlantic Forest regrowth remnant through the period 1955–2006. On the one hand, the two initially most abundant species, which are native to the study site, Notogynaphallia ernesti and Geoplana multicolor have declined over decades and at present do not exist in the forest remnant. The extinction of these species is most likely related with their preference for open vegetation areas, which presently do not exist in the forest remnant. On the other hand, the neotropical Geoplaninae 1 and the exotic Endeavouria septemlineata were detected in the forest only very recently. The long-term study allowed us to conclude that Geoplaninae 1 was introduced into the study area, although it is only known from the study site. Endeavouria septemlineata, an active predator of the exotic giant African snail, is originally known from Hawaii. This land flatworm species was observed repeatedly in Brazilian anthropogenic areas, and this is the first report of the species in relatively well preserved native forest, which may be evidence of an ongoing adaptive process. Monitoring of its geographic spread and its ecological role would be a good practice for preventing potential damaging effects, since it also feeds on native mollusk fauna, as we observed in lab conditions. Júlio Pedroni: Granted by CNPQ–Brazil.     

Synthesis and in vitro anti Mycobacterium tuberculosis activity of a series of phthalimide derivatives

New phthalimide derivatives were easily prepared through condensation of phthalic anhydride and selected amines with variable yields (70–90%). All compounds (3a–l) were evaluated against Mycobacterium tuberculosis H₃₇Rv using Alamar Blue susceptibility. The compounds 3c, 3i, and 3l have the minimum inhibitory concentrations (MICs) of 3.9, 7.8, and 5.0 μg/mL, respectively, and could be considered new lead compounds in the treatment of tuberculosis and multi-drug resistant tuberculosis.     

Regeneration of the cell wall in protoplasts of Candida albicans

To assess the dynamics of synthesis of the wall by regenerating Candida albicans protoplasts deposition of chitin and mannoproteins were investigated ultrastructurally using wheat germ agglutinin conjugated with either horseradish peroxidase or colloidal gold, and Concanavalin A coupled to ferritin respectively.Freshly prepared protoplasts lacked wheat germ agglutinin receptor sites but after 1–2 h of regeneration, they were detected. After 4–5 h of regeneration, the cell wall showed a discrete structure which was only labelled with wheat germ agglutinin in thin sections. At this stage of regeneration the outermost layer of the wall was labelled with clusters of Concanavalin A-ferritin particles.After 8 h regeneration, the cell wall appeared compact, and homogenously marked with wheat germ agglutinin whereas only the surface layers appeared consistently labelled with Concanavalin A-ferritin.From these observations we conclude that C. albicans protoplasts are able to regenerate in liquid medium a cell wall consisting of a network of chitin fibrils and mannoproteins at least (glucan polymers were not determined in the present cytological study). The former are the fundamental component of the inner layers at early stages of regeneration, whereas the latter molecules are predominant in the outer layers of the wall.Abbreviations WGA-HRP wheat germ agglutinin conjugated with horseradish peroxidase - WGA-Au wheat germ agglutinin conjugated with colloidal gold - Con A-ferritin Concanavalin A coupled to ferritin     

Reversal of depressed miduterine arterial flow during hyperthermia-induced respiratory alkalosis

The influence of ambient and arterial PCO2 on miduterine arterial flow of pregnant sheep acutely exposed to hot environments was investigated. Five mixed-breed ewes between 120 and 130 days of gestation were subjected to hot environments (increasing from thermoneutral 23 to 40 degrees C), and arterial blood pH, PCO2, and PO2 were determined at 5-min intervals. Respiratory rate, heart rate, rectal temperature, blood pressure, and miduterine arterial flow were continuously monitored prior to and during elevation of ambient air temperature. When miduterine arterial flow had decreased to 50% of thermoneutral control levels, ambient air CO2 was increased to 2.5%. Elevated ambient inspired CO2 caused a reversal in arterial pH and PCO2 to near thermoneutral levels. Miduterine arterial flow increased to 77% of the control levels following the elevated ambient PCO2 period. Respiratory rate also decreased when ambient CO2 was increased but remained 136% greater than the thermoneutral control level. All other parameters remained near their heat stress (40 degrees C) level during the elevation of ambient CO2. These data indicate that heat-stress-induced depression of miduterine arterial flow is vasoactively regulated, and cause-effect related to both arterial pH and PCO2, and thermoregulatory shunting of blood to heat-dissipating surfaces.     

Biological control of Pythium damping‐off by seed‐treatment with pseudomonas putida: Relationship with ethanol production by pea and soybean seeds

The relationship between biocontrol activity of Pseudomonas putida strain N1R against Pythium ultimum on pea and soybean seeds and the reduction in ethanol evolution by imbibed seeds was investigated under different treatment conditions, including temperature and numbers of seed‐applied cells of the bacterium. Treatment with strain N1R increased emergence at all temperatures, except for soybean at 12 °C and reduced ethanol concentration in the spermosphere of imbibed seeds at several temperatures. The concentration of bacterial cells in the seed treatment suspension also significantly affected biocontrol efficiency and reduced ethanol production, especially in pea seeds. In contrast, the duration (0–7 h) of submergence of seeds in bacterial suspension had little effect on biocontrol activity of N1R, although submergence of soybean seeds reduced their emergence even in the absence of the pathogen or biocontrol agent. Competition for seed‐derived compounds, including ethanol, is suggested to be one possible mechanism of biocontrol of Pythium by strain N1R, which is not known to produce antifungal antibiotics.     

Glutamic acid decarboxylase of embryonic avian retina cells in culture: Regulation byγ-aminobutyric acid (GABA)

1. Retina-cell aggregate cultures expressed glutamate decarboxylase activity (L-glutamate 1-carboxylase; EC 4.1.1.15) as a function of culture differentiation. 2. Glutamic acid decarboxylase (GAD) activity was low in the initial phases of culture and increased eight-fold until culture day 7, remaining high up to day 13 (last stage studied). 3. The addition of GABA to the culture medium 24 h after cell seeding almost totally prevented the expression of GAD activity. 4. In association with decreased enzyme activity, aggregates exposed to GABA did not display immunoreactivity for GAD, suggesting that GAD molecules were either lost from GABAergic neurons or significantly altered with GABA treatment. 5. Control, untreated aggregates showed intense GAD immunoreactivity in neurons. Positive cell bodies were characterized by a thin rim of labeled cytoplasm with thickest labeling at the emergence of the main neurite. 6. Heavily labeled patches were also observed throughout the aggregates, possibly reflecting regions enriched in neurites. 7. The GABA-mediated reduction of GAD immunoreactivity was a reversible phenomenon and could be prevented by picrotoxin.     

An electron microscopy study of wall expansion during Candida albicans yeast and mycelial growth using concanavalin A-ferritin labelling of mannoproteins

Depending upon growth temperature, Candida albicans can exhibit two different morphologies, a budding yeast or a mycelium. By studying the distribution of concanavalin A-ferritin particles on the cell wall surface during bud and germ tube formation, we have elucidated the way cell wall extension occurs. Both processes initially require the localized lysis of the wall in order to allow the incorporation of the newly synthesized material. Later on, the cell wall behaves as an elastic structure, allowing extension by an intosusception process and, as a consequence, cell growth.Abbreviation Con A concanavalin A