Ecology and evolution of mammalian biodiversity

Mammals have incredible biological diversity, showing extreme flexibility in eco-morphology, physiology, life history and behaviour across their evolutionary history. Undoubtedly, mammals play an important role in ecosystems by providing essential services such as regulating insect populations, seed dispersal and pollination and act as indicators of general ecosystem health. However, the macroecological and macroevolutionary processes underpinning past and present biodiversity patterns are only beginning to be explored on a global scale. It is also particularly important, in the face of the global extinction crisis, to understand these processes in order to be able to use this knowledge to prevent future biodiversity loss and loss of ecosystem services. Unfortunately, efforts to understand mammalian biodiversity have been hampered by a lack of data. New data compilations on current species' distributions, ecologies and evolutionary histories now allow an integrated approach to understand this biodiversity. We review and synthesize these new studies, exploring the past and present ecology and evolution of mammalian biodiversity, and use these findings to speculate about the mammals of our future.     

Marine-freshwater colonizations of haptophytes inferred from phylogeny of environmental 18S rDNA sequences

The Haptophyta is a common algal group in many marine environments, but only a few species have been observed in freshwaters, with DNA sequences available from just a single species, Crysochromulina parva Lackey, 1939. Here we investigate the haptophyte diversity in a high mountain lake, Lake Finsevatn, Norway, targeting the variable V4 region of the 18S rDNA gene with PCR and 454 pyrosequencing. In addition, the freshwater diversity of Pavlovophyceae was investigated by lineage-specific PCR-primers and clone library sequencing from another Norwegian lake, Lake Svaersvann. We present new freshwater phylotypes belonging to the classes Prymnesiophyceae and Pavlovophyceae, as well as a distinct group here named HAP-1. This is the first molecular evidence of a freshwater species belonging to the class Pavlovophyceae. The HAP-1 and another recently detected marine group (i.e. HAP-2) are separated from both Pavlovophyceae and Prymnesiophyceae and may constitute new higher order taxonomic lineages. As all obtained freshwater sequences of haptophytes are distantly related to the freshwater species C. parva, the phylogeny demonstrates that haptophytes colonized freshwater on multiple independent occasions. One of these colonizations, which gave rise to HAP-1, took place very early in the history of haptophytes, before the radiation of the Prymnesiophyceae.     

Effect of amino acid substitutions on the candidacidal activity of LFampin 265-284

LFampin 265-284, derived from bovine lactoferrin, has broad-spectrum antimicrobial activity against the yeast Candida albicans and several Gram-positive and Gram-negative bacteria. A glycine substitution scan was used to identify residues that are important for its candidacidal activity. Each single substitution of a positively charged residue led to considerable reduction in candidacidal activity, for each residue to a different extent. Substitution within the helix-facilitating N-terminal sequence DLIW had less severe effect; substitution of Ile and Trp led to a somewhat reduced potency. No substantial effects were found on the propensity to adopt a helical structure or to bind to C. albicans cells.     

Interaction of arsenic trioxide As2O3 with DNA and RNA

Arsenic salts have been used for centuries to treat a variety of medical conditions ranging from infectious disease to cancer. More recently, trivalent arsenic trioxide was found to exhibit high antitumor activity towards hematological malignancies. Even though much is known about antitumor activity and DNA damage by As2O3, there has been no report on the interaction of arsenic trioxide with isolated DNA or RNA. Therefore, it was of interest to examine the interaction of As2O3 with DNA and RNA in aqueous solution at physiological pH. FTIR and UV-visible difference spectroscopic methods were used to characterize the nature of drug-DNA and drug-RNA interactions and to determine the As binding site, the binding constant, the sequence selectivity, the helix stability, and the biopolymer secondary structure in the As2O3-polynucleotide complexes in vitro. The FTIR spectroscopic studies were conducted with As2O3-polynucleotide (phosphate) ratios of 1/40, 1/20, 1/10, and 1/5, with a final DNA (P) or RNA (P) concentration of 6.25 mmol/l. Spectroscopic results showed As2O3 binds to DNA and RNA at G-C, A-T, and A-U bases, and no interaction with the backbone PO2 group. As2O3-DNA and -RNA adducts showed one type of binding with overall binding constant of K(As2O3-DNA) = 1.24 x 10(5) M(-1) and K(As2O3-RNA) = 2.60 x 10(5) M(-1). The As2O3-polynucleotide complexation is associated with a partial biopolymer aggregation and no major alterations of B-DNA or A-RNA structure.     

Characterization of the HslU chaperone affinity for HslV protease

The HslVU complex is a bacterial two-component ATP-dependent protease, consisting of HslU chaperone and HslV peptidase. Investigation of protein-protein interactions using SPR in Escherichia coli HslVU and the protein substrates demonstrates that HslU and HslV have moderate affinity (Kd = 1 microM) for each other. However, the affinity of HslU for HslV fivefold increased (Kd approximately 0.2 microM) after binding with the MBP approximately SulA protein indicating the formation of a "ternary complex" of HslV-HslU-MBP approximately SulA. The molecular interaction studies also revealed that HslU strongly binds to MBP approximately SulA with 10(-9) M affinity but does not associate with nonstructured casein. Conversely, HslV does not interact with the MBP-SulA whereas it strongly binds with casein (Kd = 0.2 microM) requiring an intact active site of HslV. These findings provide evidence for "substrate-induced" stable HslVU complex formation. Presumably, the binding of HslU to MBP approximately SulA stimulates a conformational change in HslU to a high-affinity form for HslV.     

Lactoferrampin, an antimicrobial peptide of bovine lactoferrin, exerts its candidacidal activity by a cluster of positively charged residues at the C-terminus in combination with a helix-facilitating N-terminal part

The antimicrobial activity of bovine lactoferrin (bLF) is attributed to lactoferricin, which is situated in the N1-domain of bLF. Recently, another antimicrobial domain consisting of residues 268-284, designated lactoferrampin (LFampin), has been identified in the N1-domain of bLF, which exhibited antimicrobial activity against Candida albicans and several bacteria. In the present study, the candidacidal activity of a series of peptides spanning this antimicrobial domain was investigated in relation to the charge and the capacity to form a helical conformation in hydrophobic environments. C-Terminal truncation of LFampin resulted in a drastic decrease in candidacidal activity. Positively charged residues clustered at the C-terminal side of the LFampin domain appeared to be crucial for the candidacidal activity. The ability to adopt helical conformations did not change when LFampin was truncated at the C-terminal side. N-Terminally truncated LFampin peptides, truncated up to the sequence 270-284, were more reluctant to adopt a helical conformation. Therefore, we conclude that the C-terminal part of LFampin 265-284, which is the most active peptide, is crucial for its candidacidal activity, due to the presence of clustered positive charges, and that the N-terminal part is essential for activity as it facilitates helix formation.     

Bigger is not always better: when brains get smaller

Many studies assume that an increase in brain size is beneficial. However, the costs of producing and maintaining a brain are high, and we argue that brain size should be secondarily reduced by natural selection whenever the costs outweigh the benefits. Our results confirm this by showing that brain size is subject to bidirectional selection. Relative to the ancestral state, brain size in bats has been reduced in fast flyers, while it has increased in manoeuvrable flyers adapted to flight in complex habitats. This study emphasizes that brain reduction and enlargement are equally important, and they should both be considered when investigating brain size evolution.     

Leishmanin skin test in guinea pig with a single purified protein of Leishmania major

A series of hybridomas was produced by fusion of SP2/0 myeloma cells with spleen cells of mice immunized with Leishmania major (L. major). The reactivity of secreted monoclonal antibodies (mAbs) was evaluated against available leishmanin antigen by enzyme linked immunosorbent assay. Only one hybridoma designated as 7F9 secreted IgG1 mAb which was shown to be reactive with leishmanin. This mAb was further tested against four species of Leishmania (L. donovani, L. tropica, L. infantum, L. major) and a recombinant gp63. Among the four species tested it was shown to be only reactive with promastigotes of L. major. The antigen recognized by this mAb was purified and analyzed from both sonicated and supernatant cultures of L. major by immunoaffinity chromatography and reverse phase high performance liquid chromatography. The purified antigen, which gave a single band of 56kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis elicited a strong delayed-type hypersensitivity (DTH) reaction in guinea pigs sensitized with L. major. It was almost of the same degree as that produced by leishmanin. These results suggest that an L. major-specific antigen is an alternative as a specific diagnostic skin test reagent, which could lead to a better understanding of the mechanism of DTH in L. major.     

Influenza hemagglutinins outside of the contact zone are necessary for fusion pore expansion

Current models for membrane fusion in diverse biological processes are focused on the local action of fusion proteins present in the contact zone where the proteins anchored in one membrane might interact directly with the other membrane. Are the fusion proteins outside of the contact zone just bystanders? Here we assess the role of these "outsider" proteins in influenza virus hemagglutinin-mediated fusion between red blood cells and either hemagglutinin-expressing cells or viral particles. To selectively inhibit or enhance the actions of hemagglutinin outsiders, the antibodies that bind to hemagglutinin and proteases that cleave it were conjugated to polystyrene microspheres too large to enter the contact zone. We also involved hemagglutinin outsiders into interactions with additional red blood cells. We find the hemagglutinin outsiders to be necessary and sufficient for fusion. Interfering with the activity of the hemagglutinin outsiders inhibited fusion. Selective conversion of hemagglutinin outsiders alone into fusion-competent conformation was sufficient to achieve fusion. The discovered functional role of fusion proteins located outside of the contact zone suggests a tempting analogy to mechanisms by which proteins mediate membrane fission from outside of the fission site.