Role of streambed biofilms in the removal of biodegradable contaminants from shallow streams

Biological activity in shallow streams is dominated by biofilms which are attached to the surface of the streambed. Although biofilm kinetic models are well developed and are successfully applied to biological treatment process, they cannot be applied directly to predict water quality in shallow streams, because the area and mass-transport aspects of streambed biofilms are complicated and not defined. Therefore, the main purpose of this study was to develop area and mass-transport functions for cobble-and gravel-lined streambeds. An artificial stream was used to grow biofilms and conduct kinetic experiments on the biofilm utilization of an easily degraded sugar. Media size (i.e., cobble or gravel) and flow velocity were varied over a wide range of values typical to shallow streams. Water velocity had short-term and long-term effects on the rate of contaminant removal. The short-term effects were related to increased mass-transport kinetics for higher flow velocities, while the long-term effects also included increased surface colonization by biofilm. The cobble streambed was more sensitive to short-term changes in water velocity than was the gravel bed, and it gave faster removal kinetics. Equations to predict the mass transfer coefficients were appropriate for more than one biofilm community, as long as the same medium size was used. The simulations from the water quality models containing the biofilm reaction term were markedly different from the simulations from traditional water-quality models that use only suspended organism kinetics.U.S. Department of the InteriorU.S. Geological SurveyOpe

The influence of external factors on bacteriophages—review

The ability of bacteriophages to survive under unfavorable conditions is highly diversified. We summarize the influence of different external physical and chemical factors, such as temperature, acidity, and ions, on phage persistence. The relationships between a phage’s morphology and its survival abilities suggested by some authors are also discussed. A better understanding of the complex problem of phage sensitivity to external factors may be useful not only for those interested in pharmaceutical and agricultural applications of bacteriophages, but also for others working with phages

Renewable energy from Cyanobacteria: energy production optimization by metabolic pathway engineering

The need to develop and improve sustainable energy resources is of eminent importance due to the finite nature of our fossil fuels. This review paper deals with a third generation renewable energy resource which does not compete with our food resources, cyanobacteria. We discuss the current state of the art in developing different types of bioenergy (ethanol, biodiesel, hydrogen, etc.) from cyanobacteria. The major important biochemical pathways in cyanobacteria are highlighted, and the possibility to influence these pathways to improve the production of specific types of energy forms the major part of this review

Efficient generation of recombinant adenovirus vectors by homologous recombination in Escherichia coli.

Despite recent technical improvements, the construction of recombinant adenovirus vectors remains a time-consuming procedure which requires extensive manipulations of the viral genome in both Escherichia coli and eukaryotic cells. This report describes a novel system based on the cloning and manipulation of the full-length adenovirus genome as a stable plasmid in E. coli, by using the bacterial homologous recombination machinery. The efficiency and flexibility of the method are illustrated by the cloning of the wild-type adenovirus type 5 genome, the insertion of a constitutive promoter upstream from the E3 region, the replacement of the E1 region by an exogenous expression cassette, and the deletion of the E1 region. All recombinant viral DNAS were shown to be fully infectious in permissive cells, and the modified E3 region or the inserted foreign gene was correctly expressed in the infected cells

Reduction of bacterial indicators and bacteriophages infecting faecal bacteria in primary and secondary wastewater treatments

International audienceAims: To compare the suitability of various bacterial and viral indicators to assess the removal of faecal micro‐organisms by primary and secondary wastewater treatment processes. Methods and Results:ensp; The numbers of several bacterial indicators [faecal coliforms (FC), enterococci (ENT) and sulphite‐reducing clostridia (SRC)] and bacteriophages (somatic coliphages, F‐specific RNA phages and bacteriophages infecting Bacteroides fragilis strain RYC2056) were determined in incoming raw sewage and effluents from various primary and secondary wastewater treatment processes in several geographical areas. Reductions in the numbers of indicators were calculated as log10 reductions. Processes based on removal and mild disinfection, showed no significant differences in the elimination of any of the indicators tested or between geographical areas. In contrast, treatment processes that include strong microbial inactivation, such as lime‐aided flocculation and lagooning, showed significant differences between the log10 reductions of the various micro‐organisms studied, FC showing the highest reduction and spores of SRC and phages infecting B. fragilis the lowest. Conclusions: The microbial elimination performance of treatment processes based principally on removal and mild disinfection can be evaluated with a single indicator. In contrast, processes with additional disinfecting capabilities require more than one indicator for accurate evaluation of the treatment; bacteriophages are good candidates for use as second indicators.Significance and Impact of the Study: Bacteriophages provide additional information for the evaluation of microbial elimination in some treatment plants. The easy, fast and cheap methods available for phage determination are feasible both in industrialized and developing countries

Occurrence of bacterial indicators and bacteriophages infecting enteric bacteria in groundwater in different geographical areas

International audienceAims: The aim of this research was to determine the suitability of coliphages (bacteriophages) for assessing the microbial quality of groundwater.Methods and Results: The number of several bacterial indicators (faecal coliforms, Escherichia coli, enterococci and spores of sulfite‐reducing clostridia) and bacteriophages (somatic coliphages, F‐specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis) were determined in groundwater of aquifers in various geographical areas.Results show that the relative abundance, determined as percentages of positive detections, of the bacterial indicators and bacteriophages varies depending on the aquifer.Conclusions: A single bacterial indicator may not be enough to assess microbiological quality in certain aquifers. One bacterial indicator and a bacteriophage parameter provide more information than two bacterial indicators.Significance and Impact of the Study: Coliphages (CPH) provide different information from that provided by bacterial indicators on the microbial quality of groundwater in different geographical areas. Easy, fast and inexpensive methods for the detection of CPH are feasible in both industrialized and developing countries

Election 2020: Comparison of the American College of Physicians\u27 Vision for a Better U.S. Health Care System With the Presidential Candidates\u27 Plans

Health care in the United States costs too much, is unaffordable for too many, spends too much on administration, produces outcomes that are unfavorable compared with other countries, misaligns incentives with patient interests, and undervalues primary care and public health