The ammonia-oxidizing nitrifying population of the River Elbe estuary

Abstract: The ammonia-oxidizing bacterial population of the tidal River Elbe was analysed. In the freshwater section of the river, abundance was generally at a magnitude of 10⁴ cells per g dry weight and 10³ cells per ml in sediments and in water samples, respectively. In the brackish water region, counts decreased drastically with the increase in salinity caused by the low level of abundance of ammonia-oxidizers in the seawater. The contribution of attached ammonia-oxidizers to the total number ranged between 50 and approximately 100%, depending on the respective load with suspended particulate matter (SPM) of the water. The presence of seven distinct species of the genus Nitrosomonas was established by DNA hybridizations. Based on 16S rRNA gene partial sequence analyses, four groups, comprising phylogenetically closely related species, were defined. Dependence of ammonia oxidation on the NH₄Cl concentration, tolerance against increasing salinity and the possession of urease activity were found to be useful ecophysiological characteristics, being in accordance with phylogenetic relationships among the species.     

Climate affects the structure of mixed rain forest in southern sector of Atlantic domain in Brazil

This study aimed to analyze the influence of environmental factors in determining the variation in forest structure. We obtained the data through sampling units placed regularly in a grid of 10 km × 10 km in the state of Santa Catarina, southern Brazil. The axes of Detendred Correspondence Analysis summarized the vegetation structure and we used these as response variables in ordinary least square models, and environmental variables as predictors. Moran Eigenvector Maps were used as spatial predictors, enabling the variance partitioning. The results revealed influence of climatic factors, especially thermal and rainfall in determining the vegetation structure. The physical geography (high plateaus) and positioning below the Tropic of Capricorn line are the main static elements influencing the climate and therefore the vegetation.     

Genetic relationships in the genus Cicer L. as revealed by polyacrylamide gel electrophoresis of seed storage proteins

Summary Total seed storage protein of the cultivated chickpea, C. arietinum L., and eight other wild annual Cicer species (all 2n = 16) was separated and compared by sodium dodecyl sulphate polyacrylamide gel electrophoresis. The seed-protein profile was a conservative and species-specific trait. Relative interspecific similarities of protein patterns were estimated using Jaccard's similarity index, and a cluster analysis was performed. The resultant dendrogram generally agreed with the limited data already available on interspecific relationships in Cicer based on morphological characteristics, crossability, genome pairing in hybrids, karyotypes and isozyme analysis. The difference between the profiles of C. judaicum and C. pinnatifidum supported the idea that they are indeed two separate species. The closest relative of C. arietinum was C. reticulatum, followed by C. echinospermum and other species, while C. cuneatum was the farthest relative. In general, C. cuneatum was also genetically the farthest removed from any other species. The suggestion that C. reticulatum is the wild progenitor of the cultivated chickpea was therefore further supported.     

Effects of resource availability on plant recruitment at the community level in a Mediterranean mountain ecosystem

Coexisting plant species usually differ in resource requirements, which may also vary within species at successive demographic stages. Such differences become extremely important during the early life stages, since these are the most critical phases in woody-species recruitment, they depend heavily on resources, and they may determine future community composition. Under a global-change scenario, where climatic conditions, nutrient availability, and habitat characteristics are expected to be altered, it is difficult to predict the way in which plant recruitment will be affected. To understand the impact of different global-change drivers on community recruitment, we sowed a set of species representative of the different successional groups of a complete Mediterranean woody community under field conditions, and studied their emergence, growth, and survival along the main resource gradients of light, water, and nutrients. The light and nutrient gradients followed the natural range of conditions in the study area, but water availability was manipulated to simulate three contrasting climatic scenarios: wetter, drier, and current conditions. Structural equation modelling was used to provide a comprehensive analysis of the factors and relations governing plant recruitment. Overall, seedling emergence was determined directly by light; growth was determined by light and summer soil moisture; and survival was determined by summer soil moisture. Light was the main factor indirectly affecting the demographic stages of all species. However, the magnitude of the direct and indirect relationships varied among species. Particularly, species differed in their response to the expected drier climatic conditions, some (e.g. Pinus sylvestris, Acer opalus) being much more vulnerable than others (e.g. Cytisus scoparius, Salvia lavandulifolia). These differential responses could translate as major shifts in the structure of the overall plant community. Our results support the idea that the analysis of complex relations among essential resources is critical for accurate forecasts of the impact of climate change on community dynamics.     

陇东董志塬植被生态现状及评价

调查了甘肃省庆阳市董志塬的自然植被,结果表明:董志塬主要自然群落类型包括3个植被型,4个植被亚型,14个群。共记录植物33科65属165种,以菊科(Compositae)、禾本科(Gramineae)、豆科(Leguminosae)、蔷薇科(Rosaceae)居多。塬内各植物群落生物量处于"Va～Ⅱ"水平,其中森林群落"Ⅲ～Ⅱ"、灌丛、草原群落"Va～Ⅳ";生长量处于"Vb～Ⅱ",其中森林"Ⅲ～Ⅱ"、灌丛群落"Ⅳ～Ⅲ"、草原"Vb～Ⅲ";物种量处于"Va～Ⅲ"水平,其中森林和灌丛群落"Va～Ⅳ"、草原"Ⅳ～Ⅲ";群落郁闭度处于"Ⅳ～Ⅱ"水平,其中森林和灌丛为"Ⅳ～Ⅱ"、草原"Ⅳ～Ⅲ";群落结构度处于"Ⅳ～Ⅰ"水平,其中森林植被"Ⅱ～Ⅰ"、灌丛群落"Ⅳ～Ⅱ"、草丛群落"Ⅳ～Ⅲ"。综合各群落盖度、物种量、生物量、生长量、群落结构等5项指标进行评价,董志塬内各天然植被群落类型综合评价等级为"Ⅳ～Ⅱ"的水平,其中森林群落综合水平均为"Ⅲ～Ⅱ",灌丛群落和草原群落处于"Ⅳ～Ⅲ"水平。     

Syntheses and studies of amamistatin B analogs reveals that anticancer activity is relatively independent of stereochemistry, ester or amide linkage and select replacement of one of the metal chelating groups

A series of analogs of the amamistatin natural products was designed and synthesized to facilitate additional anticancer structure-activity relationships. The results indicate that the anticancer activity is relatively independent of stereochemistry, ester or amide linkage and replacement of the oxazoline/oxazole based iron-binding group with a catechol.     

Varic acid analogues from fungus as PTP1B inhibitors: Biological evaluation and structure–activity relationships

Protein tyrosine phosphatase 1B (PTP1B) inhibitors as potential therapies for diabetes and obesity have attracted much attention in recent years. Six varic acid analogues were isolated from two strains of fungi and evaluated for PTP1B inhibition activities. The structure-activity relationships were also characterized and predicted by molecular modeling. Further kinetic studies indicated the reversible and competitive inhibition manner of varic acid analogues. Trivaric acid showed insulin-sensitizing effect not only in vitro but also in vivo, representing a promising lead compound for further optimization.     

Edgetic perturbation models of human inherited disorders

Cellular functions are mediated through complex systems of macromolecules and metabolites linked through biochemical and physical interactions, represented in interactome models as ‘nodes’ and ‘edges’, respectively. Better understanding of genotype‐to‐phenotype relationships in human disease will require modeling of how disease‐causing mutations affect systems or interactome properties. Here we investigate how perturbations of interactome networks may differ between complete loss of gene products (‘node removal’) and interaction‐specific or edge‐specific (‘edgetic’) alterations. Global computational analyses of ～50 000 known causative mutations in human Mendelian disorders revealed clear separations of mutations probably corresponding to those of node removal versus edgetic perturbations. Experimental characterization of mutant alleles in various disorders identified diverse edgetic interaction profiles of mutant proteins, which correlated with distinct structural properties of disease proteins and disease mechanisms. Edgetic perturbations seem to confer distinct functional consequences from node removal because a large fraction of cases in which a single gene is linked to multiple disorders can be modeled by distinguishing edgetic network perturbations. Edgetic network perturbation models might improve both the understanding of dissemination of disease alleles in human populations and the development of molecular therapeutic strategies.     

Deciphering the virus‐to‐prokaryote ratio (VPR): insights into virus–host relationships in a variety of ecosystems

The discovery of the numerical importance of viruses in a variety of (aquatic) ecosystems has changed our perception of their importance in microbial processes. Bacteria and Archaea undoubtedly represent the most abundant cellular life forms on Earth and past estimates of viral numbers (represented mainly by viruses infecting prokaryotes) have indicated abundances at least one order of magnitude higher than that of their cellular hosts. Such dominance has been reflected most often by the virus‐to‐prokaryote ratio (VPR), proposed as a proxy for the relationship between viral and prokaryotic communities. VPR values have been discussed in the literature to express viral numerical dominance (or absence of it) over their cellular hosts, but the ecological meaning and interpretation of this ratio has remained somewhat nebulous or contradictory. We gathered data from 210 publications (and additional unpublished data) on viral ecology with the aim of exploring VPR. The results are presented in three parts: the first consists of an overview of the minimal, maximal and calculated average VPR values in an extensive variety of different environments. Results indicate that VPR values fluctuate over six orders of magnitude, with variations observed within each ecosystem. The second part investigates the relationship between VPR and other indices, in order to assess whether VPR can provide insights into virus–host relationships. A positive relationship was found between VPR and viral abundance (VA), frequency of visibly infected cells (FVIC), burst size (BS), frequency of lysogenic cells (FLC) and chlorophyll a (Chl a) concentration. An inverse relationship was detected between VPR and prokaryotic abundance (PA) (in sediments), prokaryotic production (PP) and virus–host contact rates (VCR) as well as salinity and temperature. No significant relationship was found between VPR and viral production (VP), fraction of mortality from viral lysis (FMVL), viral decay rate (VDR), viral turnover (VT) or depth. Finally, we summarize our results by proposing two scenarios in two contrasting environments, based on current theories on viral ecology as well as the present results. We conclude that since VPR fluctuates in every habitat for different reasons, as it is linked to a multitude of factors related to virus–host dynamics, extreme caution should be used when inferring relationships between viruses and their hosts. Furthermore, we posit that the VPR is only useful in specific, controlled conditions, e.g. for the monitoring of fluctuations in viral and host abundance over time.