New paradigms in tropical limnology: the importance of the microbial food web

Biological invasions of aquatic plants (i.e., macrophytes) are a worldwide phenomenon, and within the last 15 years researchers have started to focus on the influence of these species on aquatic communities and ecosystem dynamics. We reviewed current literature to identify how invasive macrophyte species impact fishes and macroinvertebrates, explore how these mechanisms deviate (or not) from the accepted model of plant–fish interactions, and assess how traits that enable macrophytes to invade are linked to effects on fish and macroinvertebrate communities. We found that in certain instances, invasive macrophytes increased habitat complexity, hypoxia, allelopathic chemicals, facilitation of other exotic species, and inferior food quality leading to a decrease in abundance of native fish and macroinvertebrate species. However, mechanisms underlying invasive macrophyte impacts on fish and macroinvertebrate communities (i.e., biomass production, photosynthesis, decomposition, and substrate stabilization) were not fundamentally different than those of native macrophytes. We identified three invasive traits largely responsible for negative effects on fish and macroinvertebrate communities: increased growth rate, allelopathic chemical production, and phenotypic plasticity allowing for greater adaptation to environmental conditions than native species. We suggest that information on invasive macrophytes (including invasive traits) along with environmental data could be used to create models to better predict impacts of macrophyte invasion. However, effects of invasive macrophytes on trophic dynamics are less well-known and more research is essential to define system level processes.     

Acetonitrile-induced unfolding of porcine pepsin A: A proposal for a critical role of hydration structures in conformational stability

In order to increase understanding of the basis of the stability of the native conformational state of porcine pepsin A, a strategy based on induction and monitoring of protein denaturation was developed. Structural perturbation was achieved by adding acetonitrile (MeCN) to the protein-solvent system. MeCN was found to induce non-coincident disruption of the secondary and tertiary structural features of pepsin A. It is proposed that gross unfolding is prompted by disruption of the protein hydration pattern induced by the organic co-solvent. It should be noted that the functional properties and thermal stability of the protein were already impaired before the onset of global unfolding. Low and intermediate contents of MeCN in the protein-solvent system affected the sharpness of the thermal transition and the degree of residual structure of the heat-denatured state. The importance of hydration to the conformational stability of pepsin A in its biologically active state is discussed.     

Chitosan: An option for development of essential oil delivery systems for oral cavity care?

Microencapsulation of bioactive compounds has received increased attention in the last decade. Among the polymers used for developing microparticulated systems, chitosan has been widely cited. Obtained by deacetylation of chitin, chitosan is a natural, biodegradable, biocompatible and mucoadhesive polymer with permeability enhancement properties. These data justify its use for overcoming the reduced efficacy of conventional treatments of oral diseases. Various tests simulating the buccal environment have described controlled drug release profile and significant activity against buccal pathogens by chitosan microparticles entrapping antimicrobial agents. Considering the increasing microbial resistance to conventional antibiotics, essential oils have shown to be an important option against these pathogens. For sustained stability and prolonged release of essential oils from pharmaceutical formulations, some authors have studied the association of chitosan to them. This review disserts about the application of chitosan and essential oils on oral cavity care pointing out their association may be an interesting option.     

Spatial colonization by feral domestic catsFelis catus of former wildcatFelis silvestris silvestris home ranges

Presently, wildcatFelis silvestris silvestris Schreber, 1777 populations are fragmented and rapidly declining in most of Europe. Although habitat destruction possibly constitutes the most serious threat to wildcat survival, hybridisation with feral domestic cats is also a critical problem. However, the mechanisms that allow domestic cats to colonise former wild cat home ranges are yet unclear. The present paper describes the decrease of typical phenotypic wildcats and the increase of phenotypic domestic cats in a remote wild area of Portugal (Serra da Malcata). A field survey using box-traps and radio-tracking between 1998 and 2001 revealed that wildcats were widespread in the study area and no domestic cats were present. A second survey using camera traps between 2005 and 2007 revealed only one wildcat whereas four typical domestic phenotype individuals were photographed. The present study clearly emphasizes the need for urgent measures aimed at preserving wildcat populations. These measures should include a national census of the species and an extensive monitoring of genetic integrity of wildcat populations, followed by the elaboration of a wildcat conservation action plan.     

Cell surface display of highly pathogenic avian influenza virus hemagglutinin on the surface of Pichia pastoris cells using α‐agglutinin for production of oral vaccines

Yeast is an ideal organism to express viral antigens because yeast glycosylate proteins more similarly to mammals than bacteria. Expression of proteins in yeast is relatively fast and inexpensive. In addition to the convenience of production, for purposes of vaccination, yeast has been shown to have natural adjuvant activity making the expressed proteins more immunogenic when administered along with yeast cell wall components. Development of genetic systems to display foreign proteins on the surface of yeast via fusion to glycosylphosphatidylinositol‐anchored (GPI) proteins has further simplified the purification of recombinant proteins by not requiring harsh treatments for cellular lysis or protein purification. We have expressed the hemagglutinin protein from a highly pathogenic avian influenza (HPAI) virus [A/Egret/HK/757.2/02], subtype H5N1, on the surface of the yeast strain Pichia pastoris, as an anchored C‐terminal fusion with the Saccharomyces cerevisiae GPI‐anchored cell wall protein, α‐agglutinin. Surface expression of the hemagglutinin fusion protein was demonstrated by immunofluorescence microscopy. Functionally, the fusion protein retained hemagglutinin agglutinating activity, and oral vaccination with the yeast resulted in production of virus neutralizing antibodies. This study represents the first steps in the generation of a yeast‐based vaccine for protection against highly pathogenic strains of avian influenza. Published 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2010     

Multiplicity of aspartic proteinases from Cynara cardunculus L.

Aspartic proteinases (AP) play major roles in physiologic and pathologic scenarios in a wide range of organisms from vertebrates to plants or viruses. The present work deals with the purification and characterisation of four new APs from the cardoon Cynara cardunculus L., bringing the number of APs that have been isolated, purified and biochemically characterised from this organism to nine. This is, to our knowledge, one of the highest number of APs purified from a single organism, consistent with a specific and important biological function of these protein within C. cardunculus. These enzymes, cardosins E, F, G and H, are dimeric, glycosylated, pepstatin-sensitive APs, active at acidic pH, with a maximum activity around pH 4.3. Their primary structures were partially determined by N- and C-terminal sequence analysis, peptide mass fingerprint analysis on a MALDI-TOF/TOF instrument and by LC–MS/MS analysis on a Q-TRAP instrument. All four enzymes are present on C. cardunculus L. pistils, along with cyprosins and cardosins A and B. Their micro-heterogeneity was detected by 2D-electrophoresis and mass spectrometry. The enzymes resemble cardosin A more than they resemble cardosin B or cyprosin, with cardosin E and cardosin G being more active than cardosin A, towards the synthetic peptide KPAEFF(NO₂)AL. The specificity of these enzymes was investigated and it is shown that cardosin E, although closely related to cardosin A, exhibits different specificity. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Antimicrobial activity of some Hypericum species

The crude methanolic extracts of six species of Hypericum [H. caprifoliatum Cham. & Schlecht., H. carinatum Griseb., H. connatum Lam., H. ternum A. St. Hil., H. myrianthum Cham. & Schlecht. and H. polyanthemum Klotzsch ex Reichardt] growing in southern Brazil were analyzed for antimicrobial activity against several microorganisms (bacteria and fungi). The most active plant was H. caprifoliatum, which showed activity against Staphylococcus aureus. Only H. polyanthemum and H. ternum extracts were active against Bacillus subtilis. None of the crude methanolic extracts showed activity against S. epidermidis, Escherichia coli or Saccharomyces cerevisiae. Extracts from these species were evaluated chemically and tannin, flavonoid and phenolic acids were the prominent compounds. The plants contained quercitrin, hyperoside (except H. connatum) and, less frequently, isoquercitrin and chlorogenic acid. In contrast to H. perforatum, which has high concentrations of rutin, these species do not produce this flavonoid or it appears as traces. The tannin concentration varied between 5.1 and 16.7% in H. myrianthum and H. ternum, respectively.     

Pyrophosphate and Adenosine 5′-Diphosphate Synthesis from Phospho(enol)pyruvate: Catalysis by Phosphate Minerals and Modulation by Dimethyl Sulfoxide

Phospho(enol)pyruvate (PEP) undergoes transphosphorylation to form pyrophosphate (PPi) and adenosine 5′-diphosphate (5′-ADP) with high yields in the presence of an adsorbent surface of calcium phosphate (Pi.Ca), which is considered to be an ancient mineral with catalytic properties. PPi formation is a result of the phosphorolytic cleavage of the enol phosphate group of PEP by precipitated Pi. The synthesis of PPi is dependent on the amount of the solid matrix; it increases with the amount of adsorbed PEP and upon addition of dimethyl sulfoxide (Me₂SO), a molecule with high dipolar moment. Although it is saturated with PEP at neutral pH, the phosphorylating Pi.Ca surface becomes effective only in alkaline conditions. In a parallel reaction, PEP phosphorylates 5′-AMP to 5′-ADP with a yield that is sevenfold higher in the presence of the Pi.Ca surface than in its absence, indicating that the solid matrix promotes interaction between adsorbed molecules with a high potential for phosphoryl transfer. In contrast to phosphorolysis, this latter reaction is stimulated by Me₂SO only in homogeneous solution. It is concluded that phosphate minerals may have coadjuvated in reactions involving different phosphorylated compounds and that molecules with high dipolar moment may have acted in mildly alkaline, primitive aqueous environments to modulate phosphoryl transfer reactions catalyzed by phosphate minerals. Received: 31 January 1996 / Revised: 31 May 1996