Patterns of correlated character evolution in flightless birds: a phylogenetic approach

Given a robust phylogeny for a particular higher taxon, it is possible to map the evolution of various character changes onto the phylogeny and study the extent to which they co-occur. Of particular interest are the questions of (a) whether particular morphological changes tend to accompany changes in ecology or behaviour to which they bear a functional relationship and (b) whether changes in those ‘primary’ morphological characters tend to be associated with correlated changes in other aspects of morphology, as would be expected given the high level of morphological integration that characterizes most organisms. Here we report a study of this kind, looking at morphological correlates of the evolution of flightlessness in birds, and using the concentrated changes test to determine whether associations are significant. We find that pectoral reduction, pelvic enlargement and changes in skull morphology significantly co-occur, and that these are usually achieved through heterochrony rather than other kinds of developmental reprogramming. This revised version was published online in November 2006 with corrections to the Cover Date.     

Flavobacterium frigidimaris sp. nov., isolated from Antarctic seawater

We described the polyphasic characterization of the psychrotolerant isolated from Antarctic seawater. The strain was closely related to Flavobacterium hydatis, F. pectinovorum, and F. saccharophilum on the basis of the 16S rDNA sequence analysis. However, DNA–DNA hybridization experiments showed that the DNA-similarities between strain KUC-1^T and the reference strains of Flavobacterium were less than 30%. Therefore, we can definite a new species of Flavobacterium phylogenetically, and strain KUC-1^T can be considered to be a new species of Flavobacterium. i.e. F. frigidimaris (KUC-1^T: JCM 12218^T and DSM 15937^T; mol% G+C of DNA of the type strain is 34.5 mol%). Useful phenotypical features for discrimination of F. frigidimaris from other Flavobacterium species, such as a resistance to NaCl, optimum growth temperature, and cellular fatty acid composition, were also determined.     

Kinetics of conditioning layer formation on stainless steel immersed in seawater

Adhesion of microorganisms to surfaces in marine environments leads to biofouling. The deleterious effects of biofilm growth in the marine environment are numerous and include energy losses due to increased fluid frictional resistance or to increased heat transfer resistance, the risk of corrosion induced by microorganisms, loss of optical properties, and quality control and safety problems. Antifouling agents are generally used to protect surfaces from such a biofilm. These agents are toxic and can be persistent, causing harmful environmental and ecological effects. Moreover, the use of biocides and regular cleaning considerably increase the maintenance costs of marine industries. An improved knowledge of bio‐film adhesion mechanisms is needed for the development of an alternative approach to the currently used antifouling agents. The aim of this study is to characterise the chemical composition of the molecules first interacting with stainless steel during the period immediately following immersion in natural seawater and to elucidate the kinetics of the adsorbtion process. Proteins are shown to adhere very rapidly, closely followed by carbohydrates. The distribution on the surface of organic molecules is also examined. The ad‐sorbate on the surface is not a continuous film but a heterogeneous deposit, whose average thickness varies widely. The cleaning procedures used affect the adsorption kinetics. In particular, cleaning with hexane results in slower adsorption of nitrogen‐containing species than does cleaning in acetone.     

Uranyl mixed-ligand complex formation in artificial seawater

Abstract

The stability constants of the mixed uranyl-hydroxo-peroxo-carbonato species have been calculated. By incorporating those and including stability constants and corresponding equilibria into the developed model of seawater species distribution enables the dependence of uranyl species on pH to be evaluated. The calculations show that at seawater conditions (pH = 8), 88.3% of total uranyl-ion is in the form UO₂(CO₃)^4-, 11% is in the form UO₂(CO₃)₂(OH)^3-, and 0.5% in the UO₂(CO₃)(OH)₂^2- mixed-ligand complex form, while in the photic layer, 81.2% of uranyl-ion is in the tricarbonate complex, 10.1% in the form UO₂(CO₃)₂(OH₂)^3-, 7% as UO₂(CO₃)₂(OH)^3-, 0.5% as UO₂(CO₃)(OH)₂^4- and 0.5% as UO₂(O₂)₂^2- species.     

Iron cycling at corroding carbon steel surfaces

Surfaces of carbon steel (CS) exposed to mixed cultures of iron-oxidizing bacteria (FeOB) and dissimilatory iron-reducing bacteria (FeRB) in seawater media under aerobic conditions were rougher than surfaces of CS exposed to pure cultures of either type of microorganism. The roughened surface, demonstrated by profilometry, is an indication of loss of metal from the surface. In the presence of CS, aerobically grown FeOB produced tight, twisted helical stalks encrusted with iron oxides. When CS was exposed anaerobically in the presence of FeRB, some surface oxides were removed. However, when the same FeOB and FeRB were grown together in an aerobic medium, FeOB stalks were less encrusted with iron oxides and appeared less tightly coiled. These observations suggest that iron oxides on the stalks were reduced and solubilized by the FeRB. Roughened surfaces of CS and denuded stalks were replicated with culture combinations of different species of FeOB and FeRB under three experimental conditions. Measurements of electrochemical polarization resistance established different rates of corrosion of CS in aerobic and anaerobic media, but could not differentiate rate differences between sterile controls and inoculated exposures for a given bulk concentration of dissolved oxygen. Similarly, total iron in the electrolyte could not be used to differentiate treatments. The experiments demonstrate the potential for iron cycling (oxidation and reduction) on corroding CS in aerobic seawater media.     

Highly Efficient Sunlight‐Driven Seawater Splitting in a Photoelectrochemical Cell with Chlorine Evolved at Nanostructured WO3 Photoanode and Hydrogen Stored as Hydride within Metallic Cathode

A seawater splitting photoelectrochemical cell featuring a nanostructured tungsten trioxide photoanode that exhibits very high and stable photocurrents producing chlorine with average 70% Faradaic efficiency is described. Fabrication of the WO₃ electrodes on fluorine‐doped tin oxide substrates involves a simple solution‐based method and sequential layer‐by‐layer deposition with a progressively adjusted amount of structure‐directing agent in the precursor and a two‐step annealing. Such a procedure allows tailoring of thick, highly porous, structurally stable WO₃ films with a large internal photoactive surface area optimizing utilization of visible light wavelengths by the photoanode. With the application of an anodic potential of 0.76 V versus Ag/AgCl reference electrode (0.4 V below the thermodynamic Cl₂/Cl^? potential) in synthetic seawater, the designed WO₃ photoanodes irradiated with simulated 1 sun AM 1.5G light reach currents exceeding 4.5 mA cm^?2. Photocurrents close to 5 mA cm^?2 are attained in the case of fresh water splitting using 1 m methane–sulfonic acid supporting electrolyte with oxygen evolved at the WO₃ photoanode. The amount of formed hydrogen is determined by discharging the palladium sheet electrode employed as a cathode. Collection of hydrogen in the form of a hydride opens, more generally, the prospect of subsequently using such materials as anodes in batteries employing oxygen reduction cathodes.     

Bacterium-bacterium inhibitory interactions among psychrotrophic bacteria isolated from Antarctic seawater (Terra Nova Bay, Ross Sea)

One hundred and forty bacteria isolated from Antarctic seawater samples were examined for their ability to inhibit the growth of indigenous isolates and their sensitivity to antibacterial activity expressed by one another. On the basis of 16S rRNA gene sequencing and analysis, bacterial isolates were assigned to five phylogenetically different taxa, Actinobacteria, alpha and gamma subclasses of Proteobacteria, Bacillaceae, and Bacteroidetes. Twenty-one isolates (15%), predominantly Actinobacteria, exhibited antagonistic properties against marine bacteria of Antarctic origin. Members of Bacteroidetes and Firmicutes did not show any inhibitory activity. Differences were observed among inhibition patterns of single isolates, suggesting that their activity was more likely strain-specific rather than dependent on phylogenetic affiliation. A novel analysis based on network theory confirmed these results, showing that the structure of this population is probably robust to perturbations, but also that it depends strongly on the most active strains. The determination of plasmid incidence in the bacterial strains investigated revealed that there was no correlation between their presence and the antagonistic activity. The data presented here provide evidence for the antagonistic interactions within bacterial strains inhabiting Antarctic seawater and suggest the potential exploitation of Antarctic bacteria as a novel source of antibiotics.     

硝态氮对海水胁迫下长春花幼苗光合特性及离子含量的影响

采用砂培试验研究了硝态氮对海水处理下长春花幼苗光合特性和离子分布的影响.结果表明：（1）高浓度海水显著抑制长春花幼苗的生长,提高硝态氮浓度能显著缓解海水胁迫对长春花幼苗生长发育的抑制作用,促进地上、地下部生物量积累.（2）随着海水浓度的增加,长春花幼苗叶片净光合速率、蒸腾速率、气孔导度和水分利用效率较对照均显著降低,细胞间隙CO2浓度显著增加;增加硝态氮浓度可显著提高长春花幼苗的净光合速率、蒸腾速率、气孔导度和水分利用效率,显著降低细胞间隙CO2浓度.（3）随着海水浓度的增加,长春花幼苗体内K＋含量较对照显著降低,而Na^＋、Cl^-含量显著增加,提高硝态氮浓度有利于长春花幼苗对K＋的吸收和向上运输,维持地上部较高的K^＋/Na^＋.研究发现,增加硝态氮能维持高浓度海水胁迫下长春花幼苗体内养分平衡,缓解盐胁迫对其光合生理和生长造成的伤害.     

Expression and activity of V‐H+‐ATPase in gill and kidney of marbled eel Anguilla marmorata in response to salinity challenge

The full‐length complementary (c)DNA of vacuolar‐type‐H⁺‐ATPase B1 gene (vhab1) in marbled eel Anguilla marmorata with 1741 base pairs (bp) was identified. It contained a 1512 bp open reading frame encoding a polypeptide with 503 amino acids (55·9 kDa), an 83 bp 5′‐untranslated region (UTR) and a 146 bp 3′‐UTR. The expression levels of A. marmorata vhab1 in gill and kidney of A. marmorata were evaluated at different intervals during the exposure to various salinities (0, 10 and 25). The results indicated that the expression levels of A. marmorata vhab1 messenger (m)RNA in gill and kidney had a significant increase and reached the highest level at 1 h in brackish water (BW, salinity 10) group and 6 h in seawater (SW, salinity 25) group. Therefore, salinity did affect the relative expression level of A. marmorata vhab1 mRNA in gills, which exhibited the enhancement by c. 44 times in SW group when compared with that in fresh water. No remarkable difference in the expression of A. marmorata vhab1 mRNA was observed after 15 days of SW exposure (P > 0·05). V‐H⁺‐ATPase activity exhibited an increase by two‐ to three‐fold when compared with that in gill and kidney from the control group. The consequence primarily suggested that A. marmorata vhab1 gene product in elvers from A. marmorata plays an important role in adaptation response to SW.     

Stainless steel in coastal seawater: sunlight counteracts biologically enhanced cathodic kinetics

The influence of sunlight of varying intensity on the performance of UNS S30400 stainless steel (SS) was explored under conditions of natural biofilm development in coastal seawater. In a series of tests performed outdoors under an opaque roof, a range of shades were fashioned to impart varied amounts of diurnal light. These were an ambient level where the underwater illumination was ~ 5% of full sunlight, two intermediate ranges of lighting with ~ 2.5% and ~ 1% of the daylight, and a condition of full darkness. In comparison with the dark, increments of sunlight rendered the SS progressively less aggressive as cathodes in galvanic couples with UNS C70600 alloy. Likewise, welded SS with pre-initiated localized corrosion sites exhibited substantially lower rates of propagation with light. Thus, biofilms and sunlight affected cathodic kinetics in opposite ways. Surface analytical tests showed that the accumulation of manganese (Mn) within the biofilms was small relative to reports from waters of lower salinity. These results not only reveal that extremely low amounts of sunlight are adequate to offset the microbial effect, but also highlight the lack of convincing evidence for Mn cycling as a potent mechanism for enhanced cathodic kinetics in full-strength seawater.