A non-linear model of phosphorus flux in the phytoplankton of a temperate eutrophic reservoir

Phosphorus fluxes in phytoplankton, between intracellular andexternal compartments have been measured, in the epilimnion ofatemperate eutrophic reservoir, by means of phosphorusdepletionexperiments performed in situ. Flow rates betweencompartments were plotted against the phosphorus concentrationofthe compartments' origin of the flows and fitted to saturationfunctions.A value of phosphorus cell subsistence quota for the wholecommunity has been computed from the X-intercept values ofeveryfunction. The obtained figures are 10–100 times higher,dependingon the reference value, than those measured running theclassicalsingle species growth response experiments in chemostats.We propose a model using five compartments and a series offlowrates between them in order to simulate the general phosphoruscycling in freshwater phytoplankton. Short term simulation ofphosphorus content in every compartment shows a fluctuatingpatternaround rates of equilibrium, in agreement with the pattern ofvariation observed in situ for the selectedcompartments.     

Social interaction in synthetic and natural microbial communities

Social interaction among cells is essential for multicellular complexity. But how do molecular networks within individual cells confer the ability to interact? And how do those same networks evolve from the evolutionary conflict between individual‐ and population‐level interests? Recent studies have dissected social interaction at the molecular level by analyzing both synthetic and natural microbial populations. These studies shed new light on the role of population structure for the evolution of cooperative interactions and revealed novel molecular mechanisms that stabilize cooperation among cells. New understanding of populations is changing our view of microbial processes, such as pathogenesis and antibiotic resistance, and suggests new ways to fight infection by exploiting social interaction. The study of social interaction is also challenging established paradigms in cancer evolution and immune system dynamics. Finding similar patterns in such diverse systems suggests that the same ‘social interaction motifs’ may be general to many cell populations.     

<Emphasis Type="Italic">Bacillus subtilis</Emphasis> bacteriocin Bac 14B with a broad inhibitory spectrum: Purification,amino acid sequence analysis,and physicochemical characterization

Bacillus subtilis strain 14B was used to produce a novel antimicrobial peptide (bacteriocin) called Bac 14B. Pure bacteriocin was obtained after heat and acidic treatments (80°C and pH 4), precipitation by ammonium sulfate, and chromatography on Sephadex G-50 and Mono Q Sepharose columns. Based on MALDI-TOF mass spectrometry analysis, purified Bac 14B is a monomer protein with a molecular mass of 20110.13 Da. N-terminal sequencing allowed for the straightforward identification of its first 12 residues, which were of a pure bacteriocin. It also revealed that this bacteriocin contained a unique sequence, namely M-L-K-A-N-L-Q-N-P-L-N-A, suggesting the identification of a novel compound. Bac 14B was stable for 1 h at temperatures up to 80°C and pH of 4 ∼ 8. It also proved sensitive to various proteases, which demonstrated its protein nature. Bac 14B displayed a bacteriolytical mode of action and a broad range of inhibitory spectra toward Gram-positive and -negative pathogens. Interestingly, based on conventional agronomic seed vigor parameters, the application of Bac 14B (500 activity units/mL) to various crops revealed that this bacteriocin was a potent exogenous enhancer of growth that stimulated the seedling vigor of tomatoes and muskmelons. Compared to those of the control, the germination percentage, shoot weight, shoot height, and root length were all significantly enhanced in Bac 14B-treated plant seeds. Bac 14B also exhibited effective disinfectant properties against a wide range of seedborne diseases and significant effects on the control of damping off diseases, particularly at the pregermination stage. It also proved to be effective against root rot diseases caused by Alternaria solani and other bacterial seedborne pathogens such as wilt diseases. The findings indicate that Bac 14B is the first B. subtilis-produced bacteriocin ever reported to exhibit such promising biological properties.     

Co-expression of the proto-oncogene fos (c-fos) and an embryonic interferon (ovine trophoblastin) by sheep conceptuses during implantation.

Expression of the c-fos proto-oncogene by ovine conceptuses was analyzed by Northern and slot blots and indirect immunohistofluorescence in relation to the expression of the embryonic interferon-alpha (oTP) during implantation. c-fos was expressed initially in the trophoblast, and then in the allantois, when this tissue began to develop (day 17). In the embryonic tissues, the c-fos proto-oncogene was weakly expressed up to day 22 and increased thereafter. In the trophoblast, the expression of c-fos proto-oncogene was transient, occurring when the oTP gene was transcribed at a maximal level at the beginning of implantation (days 14-15), and decreased thereafter, following the pattern of oTP gene expression. This decline is due essentially to the arrest of c-fos and oTP gene expression by the trophoblastic cells which established cellular contacts with the uterine epithelium during the implantation process.     

Spatial arrangement of kin affects recruitment success in young male red grouse

Models have shown that population cycles might be driven by time lags resulting from positive feedback between kin structure and population change, coupled with negative feedback between density and population change. One such model operates through kin favouritism facilitating the recruitment of young cock red grouse. We investigated whether recruitment by young cocks depended on the presence and spatial arrangement of elder relatives in the territorial population. We used molecular genetic estimates of relatedness, and checked for effects of covariates including natal territory size, hatching date, body size, parasite burdens and local density. Philopatric recruitment by cock red grouse led to the formation of clusters of contiguous territories owned by kin. The probability that an individual young cock would establish a territory increased with the number of kin in his father's cluster. This pattern might have been due to genetic quality determining both recruitment success and the size of the paternal cluster. If so, there should have been a positive correlation between a young cock's probability of recruitment and the number of his relatives in the population, irrespective of their spatial distribution. This did not occur and so the effect of cluster size is unlikely to have been confounded by genetic quality. The only morphological measure correlated with recruitment success was supraorbital comb size. The results are consistent with the prediction that kin tolerance affects recruitment but were at the level of the individual within years, rather than the population among years. Hence an experimental test of the kin favouritism hypothesis for population cycles, by manipulation of relatedness in populations among years, is now required.     

Assessment of the antiviral properties of recombinant porcine SP-D against various influenza A viruses in vitro

The emergence of influenza viruses resistant to existing classes of antiviral drugs raises concern and there is a need for novel antiviral agents that could be used therapeutically or prophylacticaly. Surfactant protein D (SP-D) belongs to the family of C-type lectins which are important effector molecules of the innate immune system with activity against bacteria and viruses, including influenza viruses. In the present study we evaluated the potential of recombinant porcine SP-D as an antiviral agent against influenza A viruses (IAVs) in vitro. To determine the range of antiviral activity, thirty IAVs of the subtypes H1N1, H3N2 and H5N1 that originated from birds, pigs and humans were selected and tested for their sensitivity to recombinant SP-D. Using these viruses it was shown by hemagglutination inhibition assay, that recombinant porcine SP-D was more potent than recombinant human SP-D and that especially higher order oligomeric forms of SP-D had the strongest antiviral activity. Porcine SP-D was active against a broad range of IAV strains and neutralized a variety of H1N1 and H3N2 IAVs, including 2009 pandemic H1N1 viruses. Using tissue sections of ferret and human trachea, we demonstrated that recombinant porcine SP-D prevented attachment of human seasonal H1N1 and H3N2 virus to receptors on epithelial cells of the upper respiratory tract. It was concluded that recombinant porcine SP-D holds promise as a novel antiviral agent against influenza and further development and evaluation in vivo seems warranted.     

Molecular fingerprinting of carbohydrate structure phenotypes of three porifera proteoglycan-like glyconectins

Glyconectins (GNs) represent a new class of proteoglycan-like cell adhesion and recognition molecules found in several Porifera species. Physico-chemical properties of GN carbohydrate moieties, such as size, composition, and resistance to most glycosaminoglycan-degrading enzymes, distinguish them from any other type of known glycoproteins. The molecular mechanism of GN-mediated self/non-self discrimination function is based on highly species-specific and Ca(2+)-dependent GN to GN associations that approach the selectivity of the evolutionarily advanced immunoglobulin superfamily. Carbohydrates of glyconectins 1, 2, and 3 are essential for species-specific auto-aggregation properties in three respective Porifera species. To obtain a structural insight into the molecular mechanisms, we performed carbohydrate structural analyses of glyconectins isolated from the three sponge model systems, Microciona prolifera (GN1), Halichondria panicea (GN2), and Cliona celata (GN3). The glycan content of all three GNs ranged between 40 and 60% of their total mass. Our approach using sequential and selective chemical degradation of GN glycans and subsequent mass spectrometric and NMR analyses revealed that each glyconectin presents novel and highly species-specific carbohydrate sequences. All three GNs include distinct acid-resistant and acid-labile carbohydrate domains, the latter composed of novel repetitive units. We have sequenced four short sulfated and one pyruvilated unit in GN1, eight larger and branched pyruvilated oligosaccharides in GN2, which represent a heterogeneous but related family of structures, and four sulfated units in GN3.