A novel method to screen genomic libraries that combines genomic immunization with the prime-boost strategy

We employed a prime-boost regimen in combination with the expression library immunization protocol to improve the protective effectiveness of a genomic library used as immunogen. To demonstrate the feasibility of this novel strategy, we used as a prime a serogroup B Neisseria meningitidis random genomic library constructed in a eukaryotic expression vector. Mice immunized with different fractions of this library and boosted with a single dose of meningococcal outer membrane vesicles elicited higher bactericidal antibody titers compared with mice primed with the empty vector. After the boost, passive administration of sera from mice primed with two of these fractions significantly reduced the number of viable bacteria in the blood of infant rats challenged with live N. meningitidis. The method proposed could be applied to the identification of subimmunogenic antigens during vaccine candidate screening by employing expression library immunization.     

Erwinia carotovora Evf antagonizes the elimination of bacteria in the gut of Drosophila larvae

Erwinia Virulence Factor (Evf) has been identified in Erwinia carotovora carotovora 15 (Ecc15) as a virulence factor that promotes colonization of the Drosophila larval gut and provokes the triggering of a systemic immune response. Here we have analysed how Evf promotes persistence and colonization of bacteria inside the larval gut. Erwinia evf mutants do not persist in immune-deficient Drosophila, indicating that Evf does not act by counteracting immunity. The results indicated that Evf is not a toxin because various gram-negative bacteria expressing evf can persist without affecting viability of Drosophila larvae. Evf did not appear to be a factor antagonizing a host-specific reaction because in vitro assays failed to reveal detoxifying enzymatic activities against various compounds thought to contribute to the hostile environment of the gut. These findings were corroborated by the observation that Evf is not required for survival in midgut organ cultures. By contrast, bacteria expressing evf allow persistence in trans of bacteria lacking evf indicating that Evf promotes the accumulation of gram-negative bacteria in the anterior midgut by affecting gut physiology.     

Dealing with scarce data to understand how environmental gradients and propagule pressure shape fine‐scale alien distribution patterns on coastal dunes

Questions: On sandy coastal habitats, factors related to substrate and to wind action vary along the sea–inland ecotone, forming a marked directional disturbance and stress gradient. Further, input of propagules of alien plant species associated to touristic exploitation and development is intense. This has contributed to establishment and spread of aliens in coastal systems. Records of alien species in databases of such heterogeneous landscapes remain scarce, posing a challenge for statistical modelling. We address this issue and attempt to shed light on the role of environmental stress/disturbance gradients and propagule pressure on invasibility of plant communities in these typical model systems. Location: Sandy coasts of Lazio (Central Italy). Methods: We proposed an innovative methodology to deal with low prevalence of alien occurrence in a data set and high cost of field‐based sampling by taking advantage, through predictive modelling, of the strong interrelation between vegetation and abiotic features in coastal dunes. We fitted generalized additive models to analyse (1) overall patterns of alien occurrence and spread and (2) specific patterns of the most common alien species recorded. Conclusion: Even in the presence of strong propagule pressure, variation in local abiotic conditions can explain differences in invasibility within a local environment, and intermediate levels of natural disturbance and stress offer the best conditions for spread of alien species. However, in our model system, propagule pressure is actually the main determinant of alien species occurrence and spread. We demonstrated that extending the information of environmental features measured in a subsample of vegetation plots through predictive modelling allows complex questions in invasion biology to be addressed without requiring disproportionate funding and sampling effort.     

B chromosomes in Nierembergia aristata (Solanaceae): nucleolar activity and competition with the A chromosomes

B chromosomes are additional dispensable chromosomes that may be present in some individuals, populations, or species, which have probably arisen from the A chromosomes but follow their own evolutionary pathway. Supposedly, B chromosomes do not contain major genes except for ribosomal DNA (rDNA) sequences that have been mapped on the supernumerary chromosomes of many plants and animals. This paper is a new report of B chromosome occurrence in plants. B chromosomes with nucleolar organizing regions (NORs) were found in a diploid sample of Nierembergiaaristata D. Don (sub nom. N. stricta Miers) (2n = 2x = 16). This is an extreme case in which B chromosomes possess not only strong nucleolar activity, as revealed by conventional staining methods, AgNOR and fluorescence banding, and fluorescent in situ hybridization (FISH), but also show nucleolar competition with the A chromosomes. The observed phenomenon could be analogous to the nucleolar dominance or 'differential amphiplasty' phenomenon that occurs in interspecific hybrids.     

Recent, independent and anthropogenic origins of Trypanosoma cruzi hybrids

The single celled eukaryote Trypanosoma cruzi, a parasite transmitted by numerous species of triatomine bug in the Americas, causes Chagas disease in humans. T. cruzi generally reproduces asexually and appears to have a clonal population structure. However, two of the six major circulating genetic lineages, TcV and TcVI, are TcII-TcIII inter-lineage hybrids that are frequently isolated from humans in regions where chronic Chagas disease is particularly severe. Nevertheless, a prevalent view is that hybridisation events in T. cruzi were evolutionarily ancient and that active recombination is of little epidemiological importance. We analysed genotypes of hybrid and non-hybrid T. cruzi strains for markers representing three distinct evolutionary rates: nuclear GPI sequences (n?=?88), mitochondrial COII-ND1 sequences (n?=?107) and 28 polymorphic microsatellite loci (n?=?35). Using Maximum Likelihood and Bayesian phylogenetic approaches we dated key evolutionary events in the T. cruzi clade including the emergence of hybrid lineages TcV and TcVI, which we estimated to have occurred within the last 60,000 years. We also found evidence for recent genetic exchange between TcIII and TcIV and between TcI and TcIV. These findings show that evolution of novel recombinants remains a potential epidemiological risk. The clearly distinguishable microsatellite genotypes of TcV and TcVI were highly heterozygous and displayed minimal intra-lineage diversity indicative of even earlier origins than sequence-based estimates. Natural hybrid genotypes resembled typical meiotic F1 progeny, however, evidence for mitochondrial introgression, absence of haploid forms and previous experimental crosses indicate that sexual reproduction in T. cruzi may involve alternatives to canonical meiosis. Overall, the data support two independent hybridisation events between TcII and TcIII and a recent, rapid spread of the hybrid progeny in domestic transmission cycles concomitant with, or as a result of, disruption of natural transmission cycles by human activities.     

Salivary PYY: a putative bypass to satiety

Peptide YY(3-36) is a satiation hormone released postprandially into the bloodstream from L-endocrine cells in the gut epithelia. In the current report, we demonstrate PYY(3-36) is also present in murine as well as in human saliva. In mice, salivary PYY(3-36) derives from plasma and is also synthesized in the taste cells in taste buds of the tongue. Moreover, the cognate receptor Y2R is abundantly expressed in the basal layer of the progenitor cells of the tongue epithelia and von Ebner's gland. The acute augmentation of salivary PYY(3-36) induced stronger satiation as demonstrated in feeding behavioral studies. The effect is mediated through the activation of the specific Y2 receptor expressed in the lingual epithelial cells. In a long-term study involving diet-induced obese (DIO) mice, a sustained increase in PYY(3-36) was achieved using viral vector-mediated gene delivery targeting salivary glands. The chronic increase in salivary PYY(3-36) resulted in a significant long-term reduction in food intake (FI) and body weight (BW). Thus this study provides evidence for new functions of the previously characterized gut peptide PYY(3-36) suggesting a potential simple and efficient alternative therapeutic approach for the treatment of obesity.     

Anuran fauna from Salta city, Argentina

The loss and transformation of habitat by anthropogenic activities is one of the main causes of biodiversity decrease. Amphibians are declining all over the world and one of the causes of this decline is thought to be habitat reduction. However, there are anuran populations in highly disturbed habitats, like cities. This study presents the ecological baseline needed to understand anuran communities in urban environments, for Salta City. Argentina (ca. 502,000 inhabitants). The sample was stratified by environments defined by infrastructure and geographic location. The species were identified by visual encounter techniques and by auditory transect during the 2002-2003 reproductive period. Three families, seven genera and twelve species were recorded and the species richness decreased from city border to center. Similarity index values among geographic areas was higher East-West (94.7) than South-West (33.3). Bufo arenarum was the only species recorded in all environments. Hyla andina and Odontophrynus americanus had a restricted distribution and are here considered vulnerable. The border effect can explain some distribution pattern in these populations. A map of the potential distribution of recorded species for Salta is provided.