Macroinfauna community structure and biochemical composition of sedimentary organic matter along a gradient of wave exposure in sandy beaches (NW Spain)

Six sandy beaches on the North West coast of Spain, exposed to different wave action, were sampled in order to study the macroinfauna community and the biopolymeric fraction (proteins, lipids and carbohydrates) of sedimentary organic matter. According to McLachlan’s rating system (1980), three of them were classified as sheltered and the other three as exposed beaches. Sampling was carried out during August 2004 at three tidal levels: high, medium and low. Macroinfauna community and organic matter concentrations were found to be significantly different when sheltered and exposed beaches were compared. Macroinfauna diversity (H′), abundances and biomass became increasingly enriched along a gradient from exposed to sheltered beaches. Macroinfauna mean abundance was found higher in sheltered (ranked from 1535 ± 358 to 15062 ± 5771 ind m⁻²) than in exposed beaches (from 150 ± 41 to 5518 ± 1986 ind m⁻²). Macroinfauna biomass ranged from 3.2 to 14.7 g m⁻² and species richness from 25 to 27 in sheltered localities; while in exposed beaches, biomass ranged from 0.2 to 2.3 g m⁻² and the number of species from 5 to 14. The biopolymeric carbon concentration (BPC) was significantly higher in sheltered (from 84.7 ± 44.7 to 163.3 ± 34.8) than in exposed (from 30.3 ± 7.5 to 78.7 ± 12.3) beaches. The low hydrodynamic conditions of sheltered beaches favoured the settlement of organic rich fine sediments, being supported by the higher protein to carbohydrate ratio found in the exposed (from 23.5 ± 0.9 to 32.7 ± 4.4), rather than in the sheltered localities (from 6.2 ± 0.7 to 13.6). Mean macroinfauna abundances were higher at medium and low tidal levels in both sheltered and exposed beaches. Crustacea was found to be the main group inhabiting the upper part of both types of beaches, dominating all tidal levels of exposed sandy beaches. Mollusca and Polychaeta groups were dominant in sheltered beaches at the medium and lower levels. There was a significant negative relationship between the BPC and the beach face slope; thus, BPC decreased as the intertidal slope increased. It seems that exposed sandy beaches are mainly physically controlled, whereas hospitable sheltered beaches let other factors, such as biochemical compounds, enrich the benthic fauna scenery. Electronic Supplementary Material  Supplementary material is available in the online version of this article at and is accessible for authorized users Handling editors: K. Martens     

Hydrogen production by Rhodopseudomonas palustris WP 3-5 in a serial photobioreactor fed with hydrogen fermentation effluent

In this study, a lab-scale serial photobioreactor composed of three column reactors was constructed and continuously operated to investigate several parameters influencing photohydrogen production when using the synthetic wastewater and the anaerobic hydrogen fermentation effluents as the influents. The results indicated that better hydrogen production rate was obtained when the serial photobioreactor was operated under cellular recycling at a short HRT of 8 h. The serial photobioreactor maintained high hydrogen content ca. 80% in the produced gas and 0.4× dilution ratio was the suitable ratio for hydrogen production. When the photobioreactor fed with the real wastewater (Effluent 1) containing 100 mg/L NH₄Cl, Column 1 reactor successfully reduced ammonia concentration to about 60 mg/L for cell synthesis, resulting in a steady hydrogen production in the following two column reactors. The average hydrogen production rate was 205 mL-H₂/L/d.     

The puhE gene of Rhodobacter capsulatus is needed for optimal transition from aerobic to photosynthetic growth and encodes a putative negative modulator of bacteriochlorophyll production

A conserved orf of previously unknown function (herein designated as puhE) is located 3' of the reaction centre H (puhA) gene in purple photosynthetic bacteria, in the order puhABCE in Rhodobacter capsulatus. Disruptions of R. capsulatus puhE resulted in a long lag in the growth of photosynthetic cultures inoculated with cells grown under high aeration, and increased the level of the peripheral antenna, light-harvesting complex 2 (LH2). The amount of the photosynthetic reaction centre (RC) and its core antenna, light-harvesting complex 1 (LH1), was reduced; however, there was no decrease in expression of a lacZ reporter fused to the puf (RC and LH1) promoter, in RC assembly in the absence of LH1, or in LH1 assembly in the absence of the RC. In strains that lack LH2, disruption of puhE increased the in vivo absorption at 780 nm, which we attribute to excess bacteriochlorophyll a (BChl) pigment production. This effect was seen in the presence and absence of PufQ, a protein that stimulates BChl biosynthesis. Expression of puhE from a plasmid reduced A(780) production in puhE mutants. We suggest that PuhE modulates BChl biosynthesis independently of PufQ, and that the presence of excess BChl in PuhE(-)LH2(+) strains results in excess LH2 assembly and also interferes with the adaptation of cells during the transition from aerobic respiratory to anaerobic photosynthetic growth.     

Phosphotyrosyl peptides and analogues as substrates and inhibitors of purple acid phosphatases

Purple acid phosphatases are metal-containing hydrolases. While their precise biological role(s) is unknown, the mammalian enzyme has been linked in a variety of biological circumstances (e.g., osteoporosis) with increased bone resorption. Inhibition of the human enzyme is a possible strategy for the treatment of bone-resorptive diseases such as osteoporosis. Previously, we determined the crystal structure of pig purple acid phosphatase to 1.55A and we showed that it is a good model for the human enzyme. Here, a study of the pH dependence of its kinetic parameters showed that the pig enzyme is most efficient at pH values similar to those encountered in the osteoclast resorptive space. Based on the observation that phosphotyrosine-containing peptides are good substrates for pig purple acid phosphatase, peptides containing a range of phosphotyrosine mimetics were synthesized. Kinetic analysis showed that they act as potent inhibitors of mammalian and plant purple acid phosphatases, with the best inhibitors exhibiting low micromolar inhibition constants at pH 3-5. These compounds are thus the most potent organic inhibitors yet reported for the purple acid phosphatases.     

Keynote papers on sandhopper orientation and navigation

This article analyses the relevant studies that have made sandhoppers a model subject for the study of orientation, and traces the development of the paradigm through innovative hypotheses and empirical evidence. Sandhoppers are able to maintain their direction without sensorial contact with the goal, which is their burrowing zone extended along the beach, but very narrow across it. They actively determine the direction of their movements, according to their internal state and the environmental features encountered. Each population shows an 'innate directional tendency' adapted to the shoreline of origin, and the inexpert laboratory-born young behave in a similar way to the adults. Genetic differences have been demonstrated between, as well as within natural populations. The question of the calibration of the sun compass to orientation on a particular shoreline implies a redundancy of mechanisms of orientation. Orientation mechanisms may involve environmental cues perceived through diverse sensory modalities, and range from simple orientation reflexes to sun compass navigational systems. These include scototaxis and geotaxis, and the response to the silhouette of the dune, in addition to sun and moon orientation, which is dependent on the time of the day and orientates daily migrations on the beach. Different modalities of orientation may operate singly, or in conjunction with each other, and their ecological significance may vary according to the habitat and lifestyle of the animals. Taken collectively, the orientation behaviour of the group appears to be a most accommodating phenotype, with considerable adaptive potential. The evidence from comparative studies of different populations promotes consideration of behavioural plasticity as an adaptation to changing coastlines.     

南京紫金山风景区紫堇属观赏植物调查及开发应用前景

通过对南京紫金山紫堇属野生观赏植物资源现状的调查,结合相关资料,从观赏特性、生态习性、园林应用等方面探讨了紫金山紫堇属植物的应用方向和前景,以期对紫堇属野生观赏植物资源的保护、开发、利用提供参考。     

Comparison of different signal peptides for protein secretion in nonlytic insect cell system

Protein expression and secretion in insect cells have been widely studied in the baculovirus-infected insect cell system. In directly transfected insect cells only intracellular expression and purification of recombinant proteins have been studied in detail. To examine multiple recombinant protein variants, easy and fast expression and a purification screening system are required. The aim of this study was to establish an effective and rapid secretion system for human azurocidin using directly transfected insect cells. We also constructed and tested expression vectors possessing heterologous signal peptides derived from human azurocidin, yellow lupin diphosphonucleotide phosphatase/phosphodiesterase (PPD1), and papaya papain IV to secrete yellow lupin and red kidney bean purple acid phosphatases, PPD1, and papain IV. Our results demonstrate that the secretion vectors used here can direct recombinant proteins to the culture medium very effectively, allowing their simple purification on a small/medium scale. Based on secretion and activity analyses it seems that the azurocidin signal peptide is one of the most potent secretion signals.     

The photosynthetic deficiency due to puhC gene deletion in Rhodobacter capsulatus suggests a PuhC protein-dependent process of RC/LH1/PufX complex reorganization

Optimal photosynthetic reaction centre (RC) and core antenna (LH1) levels in the purple bacterium Rhodobacter capsulatus require the puhC gene. Deletion of puhC had little effect on RC and LH1 assembly individually, but significantly inhibited the photosynthetic growth of RC+ LH1- strains, suggesting that maximal RC catalytic activity is PuhC-dependent. Consistent with post-assembly reorganization of the RC/LH1/PufX core complex by PuhC to include latecomer proteins, spatial separation of pufX from the RC/LH1 genes inhibited PufX accumulation and photosynthetic growth only in PuhC- strains. Photosynthetic activity improved to different degrees when PuhC homologues from three other species were expressed in PuhC- R. capsulatus, indicating that PuhC homologues function similarly but may interact inefficiently with a heterologous core complex. Anaerobic photosynthetic growth of PuhC- strains was affected by the duration of prior semiaerobic growth, and by two genes that modulate bacteriochlorophyll production: pufQ and puhE. These observations agree with a speculative model in which reorganization of the core complex is an important regenerative process, accelerated by PuhC.     

The PucC protein of Rhodobacter capsulatus mitigates an inhibitory effect of light-harvesting 2 α and β proteins on light-harvesting complex 1

Rhodobacter capsulatus contains lhaA and pucC genes that have been implicated in light-harvesting complex 1 and 2 (LH1 and LH2) assembly. The proteins encoded by these genes, and homologues in other photosynthetic organisms, have been classified as the bacteriochlorophyll delivery (BCD) family of the major facilitator superfamily. A new BCD family phylogenetic tree reveals that several PucC, LhaA and Orf428-related sequences each form separate clusters, while plant and cyanobacterial homologues cluster more distantly. The PucC protein is encoded in the pucBACDE superoperon which also codes for LH2 α (PucA) and β (PucB) proteins. PucC was previously shown to be necessary for formation of LH2. This article gives evidence indicating that PucC has a shepherding activity that keeps the homologous α and β proteins of LH1 and LH2 apart, allowing LH1 to assemble properly. This shepherding function was indicated by a 62% reduction in LH1 levels in ΔLHII strains carrying plasmids encoding pucBA along with a C-terminally truncated pucC gene. More severe reductions in LH1 were seen when the truncated pucC gene was co-expressed in the presence of C-terminal PucC::PhoA fusion proteins. It appears that interaction between truncated PucC::PhoA fusion proteins and the truncated PucC protein disrupts LH1 assembly, pointing towards a PucC dimeric or multimeric functional unit.     

Probing binding site of bacteriochlorophyll a and carotenoid in the reconstituted LH1 complex from Rhodospirillum rubrum S1 by Stark spectroscopy

Stark spectroscopy is a powerful technique to investigate the electrostatic interactions between pigments as well as between the pigments and the proteins in photosynthetic pigment–protein complexes. In this study, Stark spectroscopy has been used to determine two nonlinear optical parameters (polarizability change Tr(Δα) and static dipole-moment change |Δμ| upon photoexcitation) of isolated and of reconstituted LH1 complexes from the purple photosynthetic bacterium, Rhodospirillum (Rs.) rubrum. The integral LH1 complex was prepared from Rs. rubrum S1, while the reconstituted complex was assembled by addition of purified carotenoid (all-trans-spirilloxanthin) to the monomeric subunit of LH1 from Rs. rubrum S1. The reconstituted LH1 complex has its Q_y absorption maximum at 878 nm. This is shifted to the blue by 3 nm in comparison to the isolated LH1 complex. The energy transfer efficiency from carotenoid to bacteriochlorophyll a (BChl a), which was determined by fluorescence excitation spectroscopy of the reconstituted LH1 complex, is increased to 40%, while the efficiency in the isolated LH1 complex is only 28%. Based on the differences in the values of Tr(Δα) and |Δμ|, between these two preparations, we can calculate the change in the electric field around the BChl a molecules in the two situations to be E _Δ ≈ 3.4 × 10⁵ [V/cm]. This change can explain the 3 nm wavelength shift of the Q_y absorption band in the reconstituted LH1 complex.