The effect of oligolysines Lys-3, Lys-4, and Lys-5 on the outer membrane permeability of Pseudomonas aeruginosa

A lysine polymer with five residues (Lys-5) was found to remarkably increase the outer membrane (OM) permeability of Pseudomonas aeruginosa to the tested hydrophobic probes (nitrocefin, N-phenyl naphthylamine, rifampin). Lys-3 and Lys-4 were inactive. The OM of Escherichia coli and Salmonella typhimurium was not permeabilized by Lys-5. Furthermore, even the action of Lys-5 on the Pseudomonas OM was abolished when the assays were performed in the presence of 150 mM NaCl instead of the low-ionic strength buffer earlier used by investigators studying the effect of polycations on the Pseudomonas OM.     

Wetland use by brood‐rearing female ducks in a boreal forest landscape: the importance of food and habitat

Habitat use by birds may be related to single or interacting effects of habitat characteristics, food resources and predators, but little is known about factors affecting habitat use by wetland species in boreal ecosystems. We surveyed brood‐rearing females and ducklings of four common boreal duck species to assess the effects of habitat structure and food resources on the use of wetlands by brood‐rearing ducks. Although wetland use by duck broods was related to habitat structure and food abundance, their relative importance varied among duck species. For the Common Goldeneye Bucephala clangula, a diving duck, aquatic invertebrates and large emerging insects were the most important factors associated with wetland use. Common Teal Anas crecca broods were observed more often on wetlands with greater Dipteran emergence, whereas in Mallard Anas platyrhynchos both habitat structure and large emerging insects were important. The occurrence of Eurasian Wigeon Anas penelope broods was related to emerging Diptera and habitat structure but the associations were not strong. The varying habitat and food requirements of common duck species could influence the success of wetland management programmes, and consideration of these factors may be particularly important for initiatives aimed at harvested species or species of conservation concern.     

Fish diversity in European lakes: geographical factors dominate over anthropogenic pressures

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Characterization,bioinformatic analysis and dithiocarbamate inhibition studies of two new α-carbonic anhydrases,CAH1 and CAH2, from the fruit fly Drosophila melanogaster

Carbonic anhydrases (CAs) are essential and ubiquitous enzymes. Thus far, there are no articles on characterization of Drosophila melanogaster α-CAs. Data from invertebrate CA studies may provide opportunities for anti-parasitic drug development because α-CAs are found in many parasite or parasite vector invertebrates. We have expressed and purified D. melanogaster CAH1 and CAH2 as proteins of molecular weights 30 kDa and 28 kDa. CAH1 is cytoplasmic whereas CAH2 is a membrane-attached protein. Both are highly active enzymes for the CO₂ hydration reaction, being efficiently inhibited by acetazolamide. CAH2 in the eye of D. melanogaster may provide a new animal model for CA-related eye diseases. A series of dithiocarbamates were also screened as inhibitors of these enzymes, with some representatives showing inhibition in the low nanomolar range.     

Analysis of evolution of carbonic anhydrases IV and XV reveals a rich history of gene duplications and a new group of isozymes

Carbonic anhydrase (CA) isozymes CA IV and CA XV are anchored on the extracellular cell surface via glycosylphosphatidylinositol (GPI) linkage. Analysis of evolution of these isozymes in vertebrates reveals an additional group of GPI-linked CAs, CA XVII, which has been lost in mammals. Our work resolves nomenclature issues in GPI-linked fish CAs. Review of expression data brings forth previously unreported tissue and cancer types in which human CA IV is expressed. Analysis of collective glycosylation patterns of GPI-linked CAs suggests functionally important regions on the protein surface.     

Bats benefit from beavers: a facilitative link between aquatic and terrestrial food webs

Bat populations are declining in many areas, partly because up to two-thirds of their wetland habitats have been lost. One natural agent creating wetlands is the beaver, which is recolonizing its former range. Beaver flowages are known for their high production of aquatic invertebrates. We tested the hypothesis that the high numbers of insects emerging from beaver flowages influences their use by foraging bats. We compared bat use and bat numbers above flowages of introduced Canadian beavers Castor canadensis and in nearby control ponds where beavers were absent. The two bat species detected, Eptesicus nilssoni and Myotis daubentoni, used beaver flowages more than non-beaver ponds. This is especially the case for Eptesicus nilssoni. Bats also seemed to forage in larger groups while above beaver ponds compared to the control ponds. Beaver flowages appeared to improve bat habitats. A plausible reason for this could be the high number of insects emerging from beaver ponds. Favouring the beaver in habitat management is a tool for creating suitable conditions for many other species, such as bats. In areas not suited for the beaver, insect production can be achieved by imitating the beaver with man-made impoundments. This is especially important in areas which have lost most of their wetlands.     

Inter- and intrasporal nuclear ribosomal gene sequence variation within one isolate of arbuscular mycorrhizal fungus, Diversispora sp.

Most molecular ecological studies of arbuscular mycorrhizal fungi (AMF) have been based on the rRNA gene sequences. However, information about intraspecific nucleotide variation is still limited in these fungi. In this study, we calculated the inter- and intrasporal nucleotide variation of Diversispora sp. EE1 using 78 cloned sequences from four spores within a ca 4960 bp fragment of the nuclear ribosomal operon spanning the near full length small ribosomal subunit (SSU) rRNA gene, the full internal transcribed spacer (ITS: ITS1-5.8S-ITS2) and ca 2740 bp of the large ribosomal subunit (LSU) rRNA gene. Data for each marker region (SSU, ITS and LSU) originated from the very same spores. Sequence variation resulting from point mutations and small indels was recorded in all regions. Highest sequence variation was observed in the ITS region at both the inter- and intrasporal levels. The ITS1 component was more variable than ITS2, whilst the 5.8S gene was the least variable component of the ITS region. Evolutionary divergence of gene copies between spores was intermediate for the LSU and lowest for the SSU. The SSU and the LSU genes had relatively similar evolutionary divergence per spore. Sequence variant richness was not exhaustive for any of the marker regions, indicating that multiple sequences per spore from multiple spores are needed when characterizing a species. This study provides reference sequences for ecological studies, permitting identification of AMF using any of the ribosomal regions or primer systems.     

The beaver as an ecosystem engineer facilitates teal breeding

Positive interactions are important in influencing communities. Facilitation is one such influence in which a species makes the environment more suitable for others species. Ecological engineers are powerful facilitators as they physically modify habitats in a way that alters resource availability. We studied the effect of beaver flooding on breeding success of a dabbling duck, the teal. Our long-term (1988-2001) study was conducted in a boreal area where dabbling ducks face resource limitation. We focused on two aspects of facilitation: resource enhancement and habitat amelioration. We found that pond use by teal broods systematically increased upon beaver flooding. Beaver ponds harboured more resource, i.e. aquatic invertebrates than undisturbed waters, and invertebrate abundance was reflected as enhanced teal brood density. Beaver inundated shores were shallower than those of other waters, making their habitat structure more favourable to ducklings. Consequently, teal brood mortality was lower in beaver ponds than in waters unaffected by beaver. In boreal areas beaver facilitate teal breeding by enhancing both resource abundance and habitat structure.