Biotic homogenization of Central European urban floras depends on residence time of alien species and habitat types

Spread of alien species may result in biotic homogenization, i.e. increasing similarity between biotas of different areas. We examined whether the flora of Central European cities is becoming homogenized because of the spread of alien species, whether the contribution of aliens to homogenization depends on residence time, and whether habitats under more intense human pressure are more homogenized. Using floristic composition data from a standardized sample of 1-ha plots located in seven habitat types in 32 cities in Central Europe, Belgium and the Netherlands, we compared homogenization effects of archaeophytes (pre-AD 1500 aliens) and neophytes (post-AD 1500 aliens) using rarefaction curves, Jaccard dissimilarity index, Mantel tests and homogenization index. We found that archaeophytes contributed to homogenization and neophytes to differentiation of floras among cities, but generally the spread of alien species caused differentiation. Differentiation was low in the most disturbed urban habitats, such as city squares, boulevards or early successional sites, but was strongest in moderately disturbed habitats, such as city parks and residential areas with an open building pattern. We conclude that biotic homogenization depends on alien plants’ residence time. Aliens introduced within the past five centuries are often rare, not yet having achieved their potential range; they therefore increase floristic differentiation. Conversely, species introduced more than five centuries ago have had sufficient time to disperse into most suitable habitats, and consequently contribute to homogenization. Although invasions may therefore initially increase biodiversity, they could ultimately lead to homogenization. These processes are faster and stronger in more disturbed habitats.     

Acid phosphomonoesterase (E.C. 3.1.3.2) location in soil

Acid phosphomonoesterase (APM) (E.C. 3.1.3.2) in soil is either of plant‐root or microbial origin. Each of these sources may be dominant in certain ecosystems. Generally, extracellular APM in soil has been reported. However, the lack of suitable methods limits investigations of APM in soil. Root‐derived APM comes from intact plant roots, root exudates, root apoplastic sap, root extracts, or mycorrhizal fungi. The significance of these sources of APM is discussed in this review being the highest in intact roots or root extracts, and within wall‐ and membrane‐bound fraction of mycorrhizal fungi. Evaluation of the location of APM has been based on extraction of fractions of APM with different types of extractants. The suitability of individual extractants and lack of these procedures as well as the need to search for other suitable solutions to increase extraction efficiency, minimalize extraction of inhibitors and solubilization of organic compounds are discussed. As APM derived from roots and soil microorganisms show different kinetic properties, and differ in their response to environmental factors, determination of the significance of root and microbial APM within ecosystems requires further research aimed at evaluating the response of P transformation to climatic and other environmental changes.     

Comparison of thermal and chemical stability of Cu–humic complexes

Purpose

The purpose of this study was to investigate relationships between chemical and thermal stabilities of Cu–humic complexes. The study of the chemical stability was based on pedological methods used for the determination of the bond strength of metal ions in soils by chemical leaching agents. The samples with various contents of the Cu(II) ions and their bond strength were put to the thermal analysis in order to correlate their thermo-oxidative behavior with their stability determined by leaching.

Materials and methods

The humic acid was extracted from the South-Moravian lignite by standard alkaline extraction. The humic sample was used in two different forms: as the solid powder and as the hydrogel prepared by the acidic precipitation of humate. Six various concentrations of copper(II) solutions were used for the complexation of the humic powder and the hydrogel, in order to study the influence of their initial concentration on both the determined stabilities of the prepared complexes. Their chemical stability was assessed in terms of the Cu(II) ions release from the humic acid structure into two different extraction agents (MgCl₂ and HCl solutions). Their thermo-oxidative behavior was investigated employing the thermogravimetry.

Results and discussion

The complexation capacity of the humic hydrogel was higher in comparison with the humic powder. The amounts extractable from the Cu–humic complexes by the used leaching agents are higher for the humic powder, which shows on the lower chemical stability. The thermal degradation of the prepared complexes proceeds in several steps and this character remains also after the removal of the mobile and the ion-exchangeable fractions by the MgCl₂. The elimination of these fractions as well as the extraction of the strongly bound Cu(II) ions shift the thermal degradation to higher temperatures. The incombustible residue increases with the Cu(II) content in the complexes except for the samples extracted by the HCl.

Conclusions

The form of humic sample used for the preparation of the Cu–humic complexes influences both the chemical stability and the thermal one. The main reason is probably a better accessibility of the functional groups in the humic gel, which enables forming stronger binding copper(II) ions. The results showed that the thermal and chemical stabilities are closely related, which corresponds with the shift of the thermal degradation to higher temperatures after removing the less stable fractions from the humic complexes.     

Biosynthesis of a vasotocin-like peptide in cell cultures from pineal glands of human fetuses

Cultured cells from pineal glands of human fetuses release into their media a substance that has antidiuretic and hydroosmotic activities. The ratio of these activities as well as their susceptibility to tryptic digestion, specific oxidative inactivation by tyrosinase, and reductive inactivation by sodium thioglycollate, indicates the presence of a basic peptide, presumably identical with arginine vasotocin. The total amount of this peptide released into the culture media during 38 days of incubation is about ten times greater than the amount contained in nonincubated pineal glands from fetuses of the same age, strongly suggesting that fetal ependymal cells from the pineal gland can synthesize in vitro a peptide similar to arginine vasotocin.     

Whole-genome shotgun sequencing of mitochondria from ancient hair shafts

Although the application of sequencing-by-synthesis techniques to DNA extracted from bones has revolutionized the study of ancient DNA, it has been plagued by large fractions of contaminating environmental DNA. The genetic analyses of hair shafts could be a solution: We present 10 previously unexamined Siberian mammoth (Mammuthus primigenius) mitochondrial genomes, sequenced with up to 48-fold coverage. The observed levels of damage-derived sequencing errors were lower than those observed in previously published frozen bone samples, even though one of the specimens was >50,000 14C years old and another had been stored for 200 years at room temperature. The method therefore sets the stage for molecular-genetic analysis of museum collections.     

Comment on "Protein sequences from mastodon and Tyrannosaurus rex revealed by mass spectrometry"

Asara et al. (Reports, 13 April 2007, p. 280) reported sequencing of Tyrannosaurus rex proteins and used them to establish the evolutionary relationships between birds and dinosaurs. We argue that the reported T. rex peptides may represent statistical artifacts and call for complete data release to enable experimental and computational verification of their findings.     

Long-term survey on Trichinella prevalence in wildlife of Slovakia

In Slovakia, monitoring the prevalence of Trichinella spp. in wildlife was performed since 2000 in the main reservoir animals, the red fox (Vulpes vulpes) and wild boar (Sus scrofa), using artificial digestion method as recommended by International Commission on Trichinellosis. The results of investigation performed in 5270 red foxes showed that Trichinella infection is widespread across Slovakia and prevalence increased significantly from 4.9% in 2000 to 20.5% in 2007. Recently, a higher Trichinella prevalence (0.11%) in wild boars was also demonstrated. The results indicate that foxes and wild boars are involved in the spread of Trichinella, although the latter host species seems to play a secondary role in the maintenance of the sylvatic cycle in Slovakia. Trichinella britovi is the predominant species circulating in Slovakia, both in foxes and wild boars, and Trichinella spiralis occurs only sporadically. Mixed infections of T. britovi and Trichinella pseudospiralis were recorded in 2005 in one wild boar from Eastern Slovakia and in 2006 in one red fox from the same region. These findings are important with respect to an outbreak caused by T. pseudospiralis in a pig farm in the same district 3 years ago. This study provides a complex picture on Trichinella occurrence in all regions of Slovakia and may be a good basis for evaluating the risk of parasite transmission to the domestic cycle and human beings.     

Deep-Sea Anemones Are Prospective Source of New Antimicrobial and Cytotoxic Compounds

The peculiarities of the survival and adaptation of deep-sea organisms raise interest in the study of their metabolites as promising drugs. In this work, the hemolytic, cytotoxic, antimicrobial, and enzyme-inhibitory activities of tentacle extracts from five species of sea anemones (Cnidaria, orders Actiniaria and Corallimorpharia) collected near the Kuril and Commander Islands of the Far East of Russia were evaluated for the first time. The extracts of Liponema brevicorne and Actinostola callosa demonstrated maximal hemolytic activity, while high cytotoxic activity against murine splenocytes and Ehrlich carcinoma cells was found in the extract of Actinostola faeculenta. The extracts of Corallimorphus cf. pilatus demonstrated the greatest activity against Ehrlich carcinoma cells but were not toxic to mouse spleen cells. Sea anemones C. cf. pilatus and Stomphia coccinea are promising sources of antimicrobial and antifungal compounds, being active against Gram-positive bacteria Bacillus subtilis, Staphylococcus aureus, and yeast Candida albicans. Moreover, all sea anemones contain α-galactosidase inhibitors. Peptide mass fingerprinting of L. brevicorne and C. cf. pilatus extracts provided a wide range of peptides, predominantly with molecular masses of 4000–5900 Da, which may belong to a known or new structural class of toxins. The obtained data allow concluding that deep-sea anemones are a promising source of compounds for drug discovery.