SCCmec in staphylococci: genes on the move

Staphylococcal cassette chromosome (SCC) elements are, so far, the only vectors described for the mecA gene encoding methicillin resistance in staphylococci. SCCmec elements are classified according to the type of recombinase they carry and their general genetic composition. SCCmec types I-V have been described, and SCC elements lacking mecA have also been reported. In this review, we summarize the current knowledge about SCC structure and distribution, including genetic variants and rudiments of the elements. Its origin is still unknown, but one assumes that staphylococcal cassette chromosome is transferred between staphylococci, and mecA-positive coagulase-negative staphylococci may be a potential reservoir for these elements. Staphylococcal genomes seem to change continuously as genetic elements move in and out, but no mechanism of transfer has been found responsible for moving SCC elements between different staphylococcal species. Observations suggesting de novo production of methicillin-resistant staphylococci and horizontal gene transfer of SCCmec will be discussed.     

Atomic force microscopy and modeling of natural elastic fibrillin polymers

A central issue in the understanding of Marfan syndrome deals with the functional architecture of fibrillin-containing microfibrils. Fibrillin-rich microfibrils are long extracellular matrix fibrillar components exhibiting a 50 nm periodic beaded-structure with a width of around 20–25 nm after rotary shadowing and a 10–12 nm diameter when observed in ultra-thin sections. They are composed of fibrillin monomers more or less associated with many other components which are, for the most part, poorly characterized up to date. They are known to be elastic but few data have been accumulated to understand their properties. Atomic force microscopy (AFM) allowed us to morphologically differentiate fibrillin-rich microfibrils from other fibrillar components and to investigate the thin structure of these beaded filaments in their native state. They showed, in AFM, a periodic beaded structure ranging from 50 to 60 nm and a width of about 40 nm. The different sizes of fibrillin-containing microfibrils previously observed after rotary shadowing and in ultra-thin sections was resolved with our technique and is revealed to be 10 nm in diameter. Each beaded microfibril appears to be composed of heterogeneous beads connected by 2–3 arms. An orientation of the microfibrils has been shown, and allows us to propose a complementary model of microfibrillar monomer association.     

Composition and distribution of zooplankton in the Laptev Sea and adjacent Nansen Basin during summer, 1993

Zooplankton composition and distribution were investigated on the Laptev Sea shelf, over the continental slope and in the adjacent deep Nansen Basin during the joint German-Russian expedition “Arctic 93” with RV Polarstern and Ivan Kireyev in August/September 1993. In the shelf area biomass decreased from west to east with the lowest values in the area influenced by the Lena river runoff. A gradual increase of biomass from the shallow to the deep area correlated with water depth. Total biomass ranged between 0.1 and 1.5 g m⁻² on the shelf and 4.7 and 7.9 g m⁻² in the adjacent Nansen Basin. On the shelf Calanus glacialis/finmarchicus dominated overall. The contribution of brackish-water taxa was low in the west, where high salinity and southward currents from the Arctic Basin supported a marine neritic community, but on the southern and eastern Laptev shelf, in the areas of freshwater influence, brackish-water taxa contributed up to 27% of the total biomass. On the slope and in deep areas a few large Arctic copepod species, Calanus glacialis, C. hyperboreus and Metridia longa, composed the bulk of biomass and determined the pattern of its vertical distribution. The export of Calanus species from the Nansen Basin onto the Laptev shelf appears to be of great importance for the shelf communities. In turn, the eastern outer shelf and slope area of the Laptev Sea are thought to have a pronounced effect on the deep basin, modifying the populations entering the central Arctic. Received: 25 March 1997 / Accepted: 18 July 1997     

Secondary metabolites from Ganoderma lucidum and Spongiporus leucomallellus

The hydrodistillates and solvent extracts of the fruit bodies of Ganoderma lucidum (Fr.) P. Karst. and Spongiporus leucomallellus (Murril) A. David were investigated. The constituents in both oils comprised hydrocarbons, monoterpenes, sesquiterpenes, and fatty acids. Major volatiles of G. lucidum were trans-anethol, R-(-)-linalool, S-(+)-carvone and alpha-bisabolol, while the essential oil of S. leucomallellus contained relatively large amounts of R-(-)-1-octene-3-ol, R-(-)-linalool, 1-hepten-3-one and (Z)-nerolidol. From the n-hexane extract of G. lucidum, the steroid ester ergosta-7,22-diene-3beta-yl pentadecanoate could be identified. From S. leucomallellus two constituents showing structures of 3,4-seco-lanostane type triterpene acids were identified as (+)-23-oxo-3,4-seco-lanosta-4(28),7(8),9(11),24(31)-tetraene-3,26-dicarboxylic acid and (+)-20-hydroxy-23-oxo-3,4-seco-lanosta-4(28),7(8),9(11),24(31)-tetraene3,26-dicarboxylic acid, respectively. Cytotoxicity and antimicrobial activity of selected compounds were investigated using standard tests.     

Ground wētā in vines of the Awatere Valley,Marlborough: biology,density and distribution

The endemic New Zealand ground wētā (Hemiandrus sp. ‘promontorius’) has a Naturally Uncommon conservation status. This is because of the paucity of information on its density and distribution. Here, the biology, density and distribution of a population of this wētā found in and around vineyards in the Awatere Valley, Marlborough was studied. Wētā density was assessed in vineyards, paddocks and shrublands in this valley. Soil moisture, penetration resistance, pH and organic matter were recorded at locations with and without wētā. Wētā density in vineyards was significantly higher than in either paddocks or shrub habitats. In vineyards, the density of this insect was significantly higher under-vines than in the inter-rows. Higher numbers of this wētā were found in moist soils that required lower force to burrow. Females laid an average of 55 eggs between March and April, which hatched in September. These findings highlight the intersection between agriculture and conservation.     

Localization of sequences regulating ancestral and acquired sites of esterase6 activity in Drosophila melanogaster

We have broadly defined the DNA regions regulating esterase6 activity in several life stages and tissue types of D. melanogaster using P- element-mediated transformation of constructs that contain the esterase6 coding region and deletions or substitutions in 5' or 3' flanking DNA. Hemolymph is a conserved ancestral site of EST6 activity in Drosophila and the primary sequences regulating its activity lie between -171 and -25 bp relative to the translation initiation site: deletion of these sequences decrease activity approximately 20-fold. Hemolymph activity is also modulated by four other DNA regions, three of which lie 5' and one of which lies 3' of the coding region. Of these, two have positive and two have negative effects, each of approximately twofold. Esterase6 activity is present also in two male reproductive tract tissues; the ejaculatory bulb, which is another ancestral activity site, and the ejaculatory duct, which is a recently acquired site within the melanogaster species subgroup. Activities in these tissues are at least in part independently regulated: activity in the ejaculatory bulb is conferred by sequences between -273 and -172 bp (threefold decrease when deleted), while activity in the ejaculatory duct is conferred by more distal sequences between -844 and -614 bp (fourfold decrease when deleted). The reproductive tract activity is further modulated by two additional DNA regions, one in 5' DNA (-613 to -284 bp; threefold decrease when deleted) and the other in 3' DNA (+1860 to +2731 bp; threefold decrease when deleted) that probably overlaps the adjacent esteraseP gene. Collating these data with previous studies suggests that expression of EST6 in the ancestral sites is mainly regulated by conserved proximal sequences while more variable distal sequences regulate expression in the acquired ejaculatory duct site.      

Preference for linking element -en- in Dutch noun-noun compounds: native speakers and second language learners of Dutch

In Dutch, variation occurs in the formation of noun-noun compound words. Some compounds always add the linking element -en- between the two nouns; some compounds never use such a linking element; and still others allow both options. The element -en- is homophonous with the regular plural ending in Dutch, and we therefore investigated if plural semantics creates a preference for the linking element -en- in novel Dutch noun-noun compounds. We also investigated if the preference for linking -en- is influenced by just meaning (i.e., a semantic plural), form (i.e., a formal plural), or perhaps both. The influence of native language on preferences for Dutch compounds was also investigated. In study 1, we tested native speakers of Dutch; in study 2, Frisian-Dutch bilinguals; and, in study 3, speakers of German with Dutch as a second language. Plurality played a role in the preferences for Dutch compound formation in all tested groups. For native speakers of Dutch, Frisian, and German, moreover, the preference for a linking element in novel Dutch compounds was influenced by both the semantic plural and the formal plural. However, these effects were smaller for the native speakers of German. These findings confirm the findings of earlier studies (e.g. Schreuder et al. in Language and Cognitive Processes 13(5):551–573, 1998) showing linking -en- to carry an intrinsic plural meaning. Kiparsky’s level-ordering hypothesis (Linguistics in the morning calm, pp. 3–91, 1982) and Pinker’s words-and-rules theory (Words and rules: the ingredients of language, 1999) are re-considered in light of the present findings.     

Brood parasitism,female condition and clutch reduction in the common eider Somateria mollisima

Conspecific brood parasitism (CBP) is an alternative reproductive tactic found in many animals with parental care. Parasitizing females lay eggs in the nests of other females (hosts) of the same species, which incubate and raise both their own and the foreign offspring. The causes and consequences of CBP are debated. Using albumen fingerprinting of eggs for accurately detecting parasitism, we here analyse its relation to female condition and clutch size in High Arctic common eiders Somateria mollissima borealis. Among 166 clutches in a Svalbard colony, 31 (19%) contained eggs from more than one female, and 40 of 670 eggs (6%) were parasitic. In 6 cases an active nest with egg(s) was taken over by another female. Many suitable nest sites were unoccupied, indicating that CBP and nest takeover are reproductive tactics, not only consequences of nest site shortage. Similarity in body mass between female categories suggests that condition does not determine whether a nesting female becomes parasitised. There was no evidence of low condition in parasites: egg size was similar in hosts and parasites, and parasitism was equally frequent early and late in the laying season. Meta‐analysis of this and 3 other eider studies shows that there is a cost of being parasitised in this precocial species: host females laid on average 7% fewer eggs than other females.     

Cellular architecture of Plasmodium falciparum-infected erythrocytes

Plasmodium falciparum is a protozoan parasite that is responsible for the most pathogenic form of human malaria. The particular virulence of this parasite derives from its ability to develop within the erythrocytes of its host and to subvert their function. The intraerythrocytic parasite devours haemoglobin, and remodels its host cell to cause adhesion to blood vessel walls. Ultrastructural studies of P. falciparum have played a major role in defining its cell architecture and in resolving cell biology controversies. Here we review some of the early studies and describe some recent developments in electron microscopy techniques that have revealed information about the organization of the parasite in the blood stage of development. We present images of P. falciparum at different stages of the life cycle and highlight some of the plasmodium-specific organelles, the haemoglobin digestive apparatus and the membrane structures that are elaborated in the host cell cytoplasm to traffic virulence proteins to the erythrocyte surface. We describe methods for whole cell ultrastructural imaging that can provide three-dimensional views of intraerythrocytic development.