Plant colonization in a gravel mine revegetated with Stylosanthes spp. in a Neotropical savanna

Tree establishment on degraded sites has failed in many tropical areas due to invasive plants and competition with herbs. The cultivation of plants that are capable of maintaining a site can avoid the dominance of invasive species. Some native species of the genus Stylosanthes (family Fabaceae) have been reported to effectively block invasive plants off ecosystems that are under restoration in Brazil. The aim of this study was therefore to evaluate the influence of perennial Stylosanthes spp. on plant colonization in a rehabilitated gravel mine in the Brazilian savanna region. Half of the mining area was sown with a mixture of three perennial Styloshantes species (treatment), while half of it remained unsown (control). The line intercept method was used to sample recruited plants within the mine after five years of site rehabilitation. Results showed that 31 plant species recruited in the gravel mine: 27 in the area sown with Stylosanthes spp. and 17 in the control area. Native species contributed for 47 % of the importance value index (IVI) in the treated area and 26 % in the control area. Two invasive exotic grasses made up 31 % of the plant community IVI in the treated area and 59 % in the control area. Perennial Stylosanthes spp. were supposed to block the development of incoming plants, but their presence actually allowed the area to be colonized by 1.6-fold more plant species than the control area. Ultimately, the area covered with Stylosanthes spp. evolved into a plant community that was more diverse and less dominated by exotic species than the control area.     

Chromosomal and electric signal diversity in three sympatric electric knifefish species (Gymnotus, Gymnotidae) from the Central Amazon Floodplain

We describe chromosomal and electric signal diversity in three sympatric species of Gymnotus (Gymnotidae) fish from the Central Amazon Floodplain. Gymnotus arapaima presents a karyotype of 2n = 44 (24 m-sm + 20st-a), G. mamiraua 2n = 54 (42 m-sm + 12st-a), and G. jonasi 2n = 52 (12 m-sm + 40st-a). No evidence for a chromosomal sexual system was observed in two species for which both males and females were analyzed (G. mamiraua and G. arapaima). In all three species the constitutive heterochromatin is located primarily in pericentromeric regions, but also at some other sites. G. arapaima and G. mamiraua exhibit simple nucleolar organizing regions (NORs) on short arms of chromosome pairs 19 and 24, respectively. Gymnotus jonasi exhibits a multiple interstitial NOR on the long arm of pairs 9 and 10, and on the short arm of pair 11. G. arapaima and G. mamiraua exhibit several additional similarities in their karyotypic formulas—reflecting the phylogenetic proximity of these species within a G. carapo group clade (based on molecular phylogenetic evidence). The chromosomal differences among these three sympatric species imply complete post-zygotic reproductive isolation. A prominent pattern of partitioning of the peak power frequency of the electric organ discharge of these three species indicates pre-zygotic reproductive isolation of mate attraction signals. We conclude by discussing the evolutionary events that may have promoted signal divergence and reproductive isolation in Gymnotus of the Central Amazon, and the role that chromosomal rearrangements may place in diversification.     

Rhodotorula sp. and Trichosporon sp. are more Virulent After a Mixed Biofilm

Mycopathologia - Rhodotorula spp. and Trichosporon spp. are opportunistic pathogens, and although an association between these two species in the same infection appears to be uncommon, it has been...     

Proteomic identification of mammalian cell surface derived glycosylphosphatidylinositol‐anchored proteins through selective glycan enrichment

Glycosylphosphatidylinositol‐anchored proteins (GPI‐APs) are an important class of glycoproteins that are tethered to the surface of mammalian cells via the lipid GPI. GPI‐APs have been implicated in many important cellular functions including cell adhesion, cell signaling, and immune regulation. Proteomic identification of mammalian GPI‐APs en masse has been limited technically by poor sensitivity for these low abundance proteins and the use of methods that destroy cell integrity. Here, we present methodology that permits identification of GPI‐APs liberated directly from the surface of intact mammalian cells through exploitation of their appended glycans to enrich for these proteins ahead of LC‐MS/MS analyses. We validate our approach in HeLa cells, identifying a greater number of GPI‐APs from intact cells than has been previously identified from isolated HeLa membranes and a lipid raft preparation. We further apply our approach to define the cohort of endogenous GPI‐APs that populate the distinct apical and basolateral membrane surfaces of polarized epithelial cell monolayers. Our approach provides a new method to achieve greater sensitivity in the identification of low abundance GPI‐APs from the surface of live cells and the nondestructive nature of the method provides new opportunities for the temporal or spatial analysis of cellular GPI‐AP expression and dynamics.     

Comparative evaluation of different preservation methods for cyanobacterial strains

Maintaining pure cultures using preservation methods is of high importance for biotechnological purposes. However, preservation does not necessarily guarantee the genetic stability of these cultures. Therefore, preservation methods are currently needed to assure viability as well as genetic, physiological, and morphological integrity across storage periods. In this study, preservation of five isolates from the microalgae and cyanobacteria collection of the Plant Biology Department, Federal University of Viçosa, Minas Gerais, Brazil was investigated via monthly analyses of cell viability, biomass recovery, and contaminant concentrations over a period of 120 days. Lyophilization was adequate for both heterocystous cyanobacteria and other strains that were able to differentiate hormogones or to synthesize thick layers of exopolysaccharides. Lyophilization was also able to maintain cultures with low levels of contaminants. Dimethyl sulfoxide was relatively efficient, though some of the strains were susceptible to its cytotoxic effects. Our results demonstrated that cryopreservation with glycerol was the most efficient method. The ability to routinely preserve cyanobacterial strains reduces costs associated with maintaining large culture collections and reduces the risks of losing particular strains or species through contamination and genetic drift. The results obtained in this study are therefore discussed in the context of the efficiency of the methods and the current need to develop suitable methods for maintenance of cyanobacterial collections.