Genetic variability in species of bats revealed by RAPD analysis

Random amplified polymorphic DNA molecular marker was utilized as a means of analyzing genetic variability in seven bat species: Molossus molossus, M. rufus, Eumops glaucinus, E. perotis, Myotis nigricans, Eptesicus furinalis, and Artibeus planirostris. The determination of genetic diversity was based on 741 bands produced by a 20-random primer set. Only eight bands were considered monomorphic to one species. The greatest number of bands and the most polymorphic condition were exhibited by M. molossus, followed by M. nigricans, A. planirostris, E. furinalis, E. glaucinus, M. rufus, and E. perotis. Nei's genetic diversity index in the seven species considering the 20 primers was not greater than 0.22, but some primers were capable of detecting values between 0.39 and 0.49. Nei's unbiased genetic distance values and the UPGMA clustering pattern show that M. molossus and M. rufus have a close genetic relationship, unlike that observed between E. perotis and E. glaucinus. The latter was clustered with A. planirostris and E. furinalis. The low values for genetic diversity and distance observed indicate a genetic conservatism in the seven species. The fluorescent in situ hybridization experiments did not confirm a monomorphic condition for the eight bands identified, demonstrating that the monomorphic bands obtained by random amplified polymorphic DNA are insufficient for the identification of bat species.     

Fungal metabolic model for tyrosinemia type 3: molecular characterization of a gene encoding a 4-hydroxy-phenyl pyruvate dioxygenase from Aspergillus nidulans

Mutations in the human HPD gene (encoding 4-hydroxyphenylpyruvic acid dioxygenase) cause hereditary tyrosinemia type 3 (HT3). We deleted the Aspergillus nidulans homologue (hpdA). We showed that the mutant strain is not able to grow in the presence of phenylalanine and that it accumulates increased concentrations of tyrosine and 4-hydroxyphenylpyruvic acid, mimicking the human HT3 phenotype.     

TLR4 recognizes Pseudallescheria boydii conidia and purified rhamnomannans

Pseudallescheria boydii (Scedosporium apiospermum) is a saprophytic fungus widespread in the environment, and has recently emerged as an agent of localized as well as disseminated infections, particularly mycetoma, in immunocompromised and immunocompetent hosts. We have previously shown that highly purified α-glucan from P. boydii activates macrophages through Toll-like receptor TLR2, however, the mechanism of P. boydii recognition by macrophage is largely unknown. In this work, we investigated the role of innate immune receptors in the recognition of P. boydii. Macrophages responded to P. boydii conidia and hyphae with secretion of proinflammatory cytokines. The activation of macrophages by P. boydii conidia required functional MyD88, TLR4, and CD14, whereas stimulation by hyphae was independent of TLR4 and TLR2 signaling. Removal of peptidorhamnomannans from P. boydii conidia abolished induction of cytokines by macrophages. A fraction highly enriched in rhamnomannans was obtained and characterized by NMR, high performance TLC, and GC-MS. Preparation of rhamnomannans derived from P. boydii triggered cytokine release by macrophages, as well as MAPKs phosphorylation and IκBα degradation. Cytokine release induced by P. boydii-derived rhamnomannans was dependent on TLR4 recognition and required the presence of non-reducing end units of rhamnose of the rhamnomannan, but not O-linked oligosaccharides from the peptidorhamnomannan. These results imply that TLR4 recognizes P. boydii conidia and this recognition is at least in part due to rhamnomannans expressed on the surface of P. boydii.     

Structural analysis of an Echinococcus granulosus actin-fragmenting protein by small-angle x-ray scattering studies and molecular modeling

The Echinococcus granulosus actin filament-fragmenting protein (EgAFFP) is a three domain member of the gelsolin family of proteins, which is antigenic to human hosts. These proteins, formed by three or six conserved domains, are involved in the dynamic rearrangements of the cytoskeleton, being responsible for severing and capping actin filaments and promoting nucleation of actin monomers. Various structures of six domain gelsolin-related proteins have been investigated, but little information on the structure of three domain members is available. In this work, the solution structure of the three domain EgAFFP has been investigated through small-angle x-ray scattering (SAXS) studies. EgAFFP exhibits an elongated molecular shape. The radius of gyration and the maximum dimension obtained by SAXS were, respectively, 2.52 +/- 0.01 nm and 8.00 +/- 1.00 nm, both in the absence and presence of Ca2+. Two different molecular homology models were built for EgAFFP, but only one was validated through SAXS studies. The predicted structure for EgAFFP consists of three repeats of a central beta-sheet sandwiched between one short and one long alpha-helix. Possible implications of the structure of EgAFFP upon actin binding are discussed.     

Chromosomes of three freshwater stingrays (Rajiformes Potamotrygonidae) from the Rio Negro basin, Amazon, Brazil

Potamotrygonidae is the representative family of South American freshwater elasmobranchs. It is a monophyletic group containing 20 species grouped into three genera. Three species belonging to two genera of this family were collected from the middle Negro River, Amazonas, Brazil, and studied cytogenetically: Paratrygon aiereba, Potamotrygon motoro and Potamotrygon orbignyi. Paratrygon aiereba presented 2n = 90 chromosomes and 4M+2SM+10ST+74A. Both species of Potamotrygon presented 2n = 66 chromosomes and differed in their chromosomal formulas: P. motoro had 18M+12SM+10ST+26A and P. orbignyi had 22M+10SM+8ST+26A. No sex heteromorphism was detected. The Fundamental Number (FN) was 106 for the three species. A system of multiple NORs was found in the three species, but with interspecific differences in terms of location and position of the active Ag-NORs sites. Paratrygon aiereba presented only four sites on the short arms of two chromosomal pairs, both in terminal regions. Potamotrygon motoro presented seven sites, on the long and short arms, all in terminal regions of non-homologous chromosomes; P. orbignyi presented eight sites on the long arms, all in terminal regions, of non-homologous chromosomes. The constitutive heterochromatin was in pericentromeric regions of all chromosomes, and no significant interspecific difference was found in relation to this marker.     

Genetic Relationships Between Brazilian Species of Molossidae and Phyllostomidae (Chiroptera, Mammalia)

A comparative analysis of G-banded karyotypes was performed for seven species of Chiroptera, representing two families (Phyllostomidae and Molossidae). Despite the differences in diploid and fundamental numbers, extensive homologies between six karyotypes were identified: A . planirostris, P. lineatus, S. lilium, G. soricina, P. hastatus (Phyllostomidae) and M. rufus (Molossidae). Robertsonian rearrangements and pericentric inversions account for the differences between the karyotypes of phyllostomid and molossid species. The homologies and rearrangements observed reinforce the monophiletic origin of phyllostomids and the inclusion of species in different subfamilies. In situ hybridization with genomic DNA revealed considerable conservation of the karyotypes, including C. perspicillata, that did not show G-band homologies with the other species analyzed. For the first time, chromosomal evidence is presented of a common origin for Phyllostomidae and Molossidae.     

Antimicrobial resistance of Pseudomonas aeruginosa biofilms

Resistance to antimicrobial agents is the most important feature of biofilm infections. As a result, infections caused by bacterial biofilms are persistent and very difficult to eradicate. Although several mechanisms have been postulated to explain reduced susceptibility to antimicrobials in bacterial biofilms, it is becoming evident that biofilm resistance is multifactorial. The contribution of each of the different mechanisms involved in biofilm resistance is now beginning to emerge.