Sediment microbial taxonomic and functional diversity in a natural salinity gradient challenge Remane’s “species minimum” concept

Several models have been developed for the description of diversity in estuaries and other brackish habitats, with the most recognized being Remane's Artenminimum (``species minimum'') concept. It was developed for the Baltic Sea, one of the world's largest semi-enclosed brackish water body with a unique permanent salinity gradient, and it argues that taxonomic diversity of macrobenthic organisms is lowest within the horohalinicum (5 to 8 psu). The aim of the present study was to investigate the relationship between salinity and sediment microbial diversity at a freshwater-marine transect in Amvrakikos Gulf (Ionian Sea, Western Greece) and assess whether species composition and community function follow a generalized concept such as Remane's. DNA was extracted from sediment samples from six stations along the aforementioned transect and sequenced for the 16S rRNA gene using high-throughput sequencing. The metabolic functions of the OTUs were predicted and the most abundant metabolic pathways were extracted. Key abiotic variables, i.e., salinity, temperature, chlorophyll-a and oxygen concentration etc., were measured and their relation with diversity and functional patterns was explored. Microbial communities were found to differ in the three habitats examined (river, lagoon and sea) with certain taxonomic groups being more abundant in the freshwater and less in the marine environment, and vice versa. Salinity was the environmental factor with the highest correlation to the microbial community pattern, while oxygen concentration was highly correlated to the metabolic functional pattern. The total number of OTUs showed a negative relationship with increasing salinity, thus the sediment microbial OTUs in this study area do not follow Remane's concept

Aristotle’s scientific contributions to the classification, nomenclature and distribution of marine organisms

The biological works of the Greek philosopher Aristotle include a significant amount of information on marine animals. This study is an overview of Aristotle’s scientific contribution to the knowledge of marine biodiversity and specifically to taxonomic classification, nomenclature and distribution of marine species. Our results show that Aristotle’s approach looks remarkably familiar to present day marine biologists since: (i) although not directly aiming at it, he gave a taxonomic classification of marine animals, which includes physical groups ranked on three levels at least; (ii) most of Aristotle’s marine “major groups” correspond to taxa of the order rank in Linnaeus’s classification and to taxa of the class rank in the current classification; (iii) a positive correlation was found between the number of taxa per group identified in Aristotle’s writings and those described by Linnaeus; (iv) Aristotle’s classification system exhibits similarities with the current one regarding the way taxa are distributed to higher categories; (v) a considerable number of Aristotle’s marine animal names have been used for the creation of the scientific names currently in use; (vi) he was the first to give an account of Mediterranean marine fauna, focusing on the Aegean Sea and adjacent areas. In view of the above, we suggest that the foundations of marine taxonomy as laid down by Aristotle are still echoing today

MarBEF, databases, and the legacy of John Gray

Within the European Network of Excellence (NoE) on Marine Biodiversity and Ecosystem Functioning (MarBEF), marine biodiversity scientists from across Europe have been brought together to focus on 3 broad themes. Theme 1 describes large-scale (and long-term) distribution patterns of marine biodiversity, Theme 2 examines the consequences of changes in marine biodiversity for the functioning of marine ecosystems, and Theme 3 explores and disseminates the socio-economic consequences of changes in marine biodiversity and biodiversity-mediated processes. Within MarBEF Theme 1, a large collaborative effort has produced an integrated database of species occurrence information (MacroBen), which contains data of quantitative samples of soft-sediment benthic infauna collected in European continental waters, from the Arctic to the Black Sea. Papers in this Theme Section describe initial studies based on the database. The late Prof. John S. Gray led activities within MarBEF Theme 1 for the first 2.5 yr, during which time the majority of the work described in this Theme Section was set in motion, and he continued to be involved in the work until his untimely death. We dedicate this body of work to his memory.

Genetic vs community diversity patterns of macrobenthic species: preliminary results from the lagoonal ecosystem

1 - The use of molecular data derived from multispecies assemblages in order to test ecological theory has only recently been introduced in the scientific literature.2 - As a first step, we compared patterns of abiotic environment, polychaeta distribution and their genetic diversity in five lagoon ecosystems in Greece. Our results confirm the hypothesis that higher genetic diversity is expected in the populations of the species occurring in the transitional waters rather than of those occurring in the marine environment.3 - Patterns derived from the polychaete community level and from the mitochondrial DNA (16S rRNA) obtained from Nephtys hombergii and Hediste diversicolor showed convergence, indicating the potential use of molecular matrices as surrogates in community analysis.4 - Finally, the high correlation between the genetic diversity pattern of H. diversicolor and the phosphorus concentration in the sediments may imply the broadening of the hierarchic-response-tostress hypothesis towards lower than species level

Elucidation of One Step Synthesis of PEGylated CuFe Bimetallic Nanoparticles. Antimicrobial Activity of CuFe@PEG vs Cu@PEG

There is a growing field of research on the physicochemical properties of bimetallic nanoparticles (BMNPs) and their potential use in different applications. Meanwhile, their antimicrobial activity is scarcely reported, although BMNPs can potentially achieve unique chemical transformations and synergetic effects can be presented. Towards this direction a reproducible simple hybrid polyol process under moderate temperature solvothermal conditions has been applied for the isolation of non-oxide contaminated bimetallic CuFe nanoparticles (NPs). 1,2-propylene glycol (PG), tetraethylene glycol (TEG) and polyethylene glycol (PEG 8000), that exhibit different physicochemical properties, have been utilized to regulate the size, structure, composition and the surface chemistry of NPs. The BMNPs were found to be of small crystalline size, 30–45 nm, and high hydrophilicity, different wt% percentage of organic coating and variable hydrodynamic size and surface charge. The antimicrobial activity of the BMNPs was evaluated against the bacterial strains B. subtilis, E. coli and fungus S. cerevisiae. The IC50 values for CuFe NPs were found significantly lower compared with Cu NPs of the same size, revealing an enhancement in the antimicrobial activity when iron and copper coexist in the crystal structure. The reactive oxygen species (ROS) production was measured intracellularly and extracellularly by the nitroblue tetrazolium assay in the fungal cultures. No extracellular ROS were measured suggesting that both CuFe and Cu NPs enter the fungal cells during the incubation, also verified by optical imaging of the fungal cells in the presence of NPs. Higher ROS concentrations were generated intracellularly for CuFe NPs supporting different red/ox reaction mechanisms

Superconductivity: Exotic Commonalities in Phase and Mode

Recent muon and neutron experiments on the new FeAs-based superconductors revealed phase diagrams characterized by first-order evolution from antiferromagnetic to superconducting states, and an inelastic magnetic resonance mode whose energy scales as $\sim 4 k_{B}T_{c}$. These features exhibit striking commonalities with cuprate, backyball, organic, and heavy-fermion superconductors as well as superfluid $^{4}$He.Comment: 4 pages, 2 figures, original version of News and Views for Nature Materials submitted on Feb. 8, 2009; revised version will appear as Nature Materials 8 (April, 2009) 253-25

Analyticity and compactness of semigroups of composition operators

This paper provides a complete characterization of quasicontractive groups and analytic C0C0-semigroups on Hardy and Dirichlet space on the unit disc with a prescribed generator of the form Af=Gf′Af=Gf′. In the analytic case we also give a complete characterization of immediately compact semigroups. When the analyticity fails, we obtain sufficient conditions for compactness and membership in the trace class. Finally, we analyse the case where the unit disc is replaced by the right-half plane, where the results are drastically different