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.     

Cytosine-specific DNA modification interferes with plasmid establishment in Escherichia coli K12: involvement of rglB

Summary Several chimeric pBR322/328 derivatives containing genes for cytosine-specific DNA methyltransferases (Mtases) can be transformed into the Escherichia coli K12/E. coli B hybrid strains HB101 and RR1 but not into other commonly used E. coli K12 strains. In vitro methylation of cytosine residues in pBR328 and other unrelated plasmids also reduces their potential to transform such methylation sensitive strains, albeit to a lesser degree than observed with plasmids containing Mtase genes. The extent of reduced transformability depends on the target specificity of the enzyme used for in vitro modification. The role of a host function in the discrimination against methylated plasmids was verified by the isolation of K12 mutants which tolerate cytosine methylated DNA. The mutations map in the vicinity of the serB locus. This and other data indicate that the host rglB function is involved in the discrimination against modified DNA.     

Redox-Bohr effect in the tetrahaem cytochrome c3 from Desulfovibrio vulgaris: a model for energy transduction mechanisms

 Using potentiometric titrations, two protons were found to participate in the redox-Bohr effect observed for cytochrome c ₃ from Desulfovibrio vulgaris (Hildenborough). Within the framework of the thermodynamic model previously presented, this finding supports the occurrence of a concerted proton-assisted 2e^– step, ideally suited for the coupling role of cytochrome c ₃ to hydrogenase. Furthermore, at physiological pH, it is shown that when sulfate-reducing bacteria use H₂ as energy source, cytochrome c ₃ can be used as a charge separation device, achieving energy transduction by energising protons which can be left in the acidic periplasmic side and transferring deenergised electrons to sulfate respiration. This mechanism for energy transduction, using a full thermodynamic data set, is compared to that put forward to explain the proton-pumping function of cytochrome c oxidase.     

Preclinical insights into the gut‐skeletal muscle axis in chronic gastrointestinal diseases

Muscle wasting represents a constant pathological feature of common chronic gastrointestinal diseases, including liver cirrhosis (LC), inflammatory bowel diseases (IBD), chronic pancreatitis (CP) and pancreatic cancer (PC), and is associated with increased morbidity and mortality. Recent clinical and experimental studies point to the existence of a gut‐skeletal muscle axis that is constituted by specific gut‐derived mediators which activate pro‐ and anti‐sarcopenic signalling pathways in skeletal muscle cells. A pathophysiological link between both organs is also provided by low‐grade systemic inflammation. Animal models of LC, IBD, CP and PC represent an important resource for mechanistic and preclinical studies on disease‐associated muscle wasting. They are also required to test and validate specific anti‐sarcopenic therapies prior to clinical application. In this article, we review frequently used rodent models of muscle wasting in the context of chronic gastrointestinal diseases, survey their specific advantages and limitations and discuss possibilities for further research activities in the field. We conclude that animal models of LC‐, IBD‐ and PC‐associated sarcopenia are an essential supplement to clinical studies because they may provide additional mechanistic insights and help to identify molecular targets for therapeutic interventions in humans.     

Endozoochory of a dry‐fruited tree aids quarry passive restoration and seed soaking further increases seedling emergence

As practitioners promote passive restoration as a complementary approach to technical reclamation, it is imperative to know its drivers. Although the consequences of endozoochory can be crucial to passive restoration success, few experimental studies assess the use of heavily disturbed sites by seed dispersers such as carnivores and how the seeds they bring in emerge and survive. Using an indoor sowing experiment conducted in a quarry located within a natural park in Portugal, we examined for the first time how carnivore endozoochorous seeds collected in the quarry potentially influence its passive restoration, through effects on plant emergence and survival. Also, we tested whether sowing date and water soaking, relevant factors when sowings are to be carried out, would affect seedling emergence and mortality rates when compared with the effect of endozoochory. Our target species were included in the revegetation plan of the quarry, of which endozoochorous seeds of Carob tree (Ceratonia siliqua) were collected in sufficient number for analysis. Irrespective of the carnivore species, endozoochorous carob seeds performed similarly to untreated seeds regarding emergence rates. Endozoochorous carob seedlings showed greater mortality rates but the net result for the plant can still be the colonization of recently vacant habitats by a large proportion of viable seeds. Concerning sowing date, the later carob seeds were sown over the fruit‐ripening season the faster seedlings emerged. Water soaking increased emergence rate by 6.5 times. Broadly, sowings with previous soaking and carnivore‐mediated seed dispersal of this dry‐fruited tree can jointly enhance quarry restoration.     

Acetylenic 2-phenylethylamides and new isobutylamides from Acmella oleracea (L.) R. K. Jansen,a Brazilian spice with larvicidal activity on Aedes aegypti

Ethanol extract obtained from dried leaves of Acmella oleracea afforded after a liquid/liquid partition procedure a larvicidal hexane fraction (LC₅₀ = 145.6 ppm) and a non larvicidal dichloromethane one. From the inactive fraction, three amides were identified, two new structures, named deca-6,9-dihydroxy-(2E,7E)-dienoic acid isobutylamide (1), deca-8,9-dihydroxy-(2E,6Z)-dienoic acid isobutylamide (2) and the known nona-2,3-dihydroxy-6,8-diynoic acid 2-phenylethylamide (3). Bioassay-guided chromatographic fractionation of the hexane partition led to the identification of an amide mixture, nona-(2Z)-en-6,8-diynoic acid 2-phenylethylamide (4) and deca-(2Z)-en-6,8-diynoic acid 2-phenylethlylamide (5). This mixture was active against Aedes aegypti larvae at LC₅₀ = 7.6 ppm. Low toxicity of crude extracts and derived fractions on Artemia salina nauplies showed the possibility of using them to control the A. aegypti mosquito larvae. This is the first report on larvicidal activity of acetylenic 2-phenylethylamides and their identification in A. oleracea leaves.     

Loss of phytoplankton functional and taxonomic diversity induced by river regulation in a large tropical river

Hydrobiologia - Human activities have disrupted the functioning of river ecosystems around the world. In the Amazon basin, hydropower expansion has affected diversity patterns, but no study has...     

Phylogeographical patterns shed light on evolutionary process in South America

The South American continent is composed of several biogeographical regions harbouring the highest biodiversity on the globe, encompassing five of the world's biodiversity ‘hot spots’. Nonetheless, the patterns and processes responsible for shaping its astonishing species diversity are largely unknown. Here, we present a review of current South American phylogeographical knowledge based on published articles on this topic. An appraisal of the literature reveals emerging phylogeographical patterns in the biota of South America. The striking phylogeographical divergence observed among organism lineages in South American studies is suggestive of high levels of undocumented species diversity. The interplay between Pleistocene climatic oscillations and Pliocene/Miocene orogenic events has contributed to shaping the current diversity and distribution of modern lineages in both the tropical and temperate regions of South America. Although older divergence times were observed for a range of species, most herpetofauna underwent an intraspecific lineage split much earlier than other organisms. The geographical ranges of species associated with forest habitats were reduced mainly during glacial cycles, whereas species associated with open vegetation domains have shown variable responses to climatic oscillations. The results suggest a highly complex mosaic of phylogeographical patterns in South America. We suggest future research directions to promote a better understanding of the origin and maintenance of the South American biota.