Streamflow and velocity as determinants of aquatic insect distribution and benthic community structure in Illinois

Stream flow characteristics, in particular velocity and depth, control channel substrates and directly or indirectly determine how aquatic insects are distributed and benthic communities are structured. A three year laboratory and field research program has been completed evaluating how streamflow affects aquatic insects in Illinois. Field studies related benthic community structure and species composition with boundary layer Reynolds number (R*) and evaluated microhabitat selection of several insect species on hydraulically defined artificial substrates. Hydraulic calibration of substrates was completed in laboratory flume studies using a thermistor based microprobe. A laboratory artificial stream was also used to determine habitat selection of net spinning caddisflies. Results indicated selection for defined microhabitats in several aquatic insect taxa. The artificial substrates proved to be a valuable tool in defining microhabitat characteristics occupied by aquatic insects. In studies to determine instream flow requirements, measures of mean column velocity were shown to be inadequate, determination of R* was preferred. The results of this research provide water resources managers with better tools to assess microhabitat modifications produced by changes in streamflow.U.S. Department of the InteriorU.S. Geological SurveyOpe

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

ODELAY: A Large-scale Method for Multi-parameter Quantification of Yeast Growth.

Growth phenotypes of microorganisms are a strong indicator of their underlying genetic fitness and can be segregated into 3 growth regimes: lag-phase, log-phase, and stationary-phase. Each growth phase can reveal different aspects of fitness that are related to various environmental and genetic conditions. High-resolution and quantitative measurements of all 3 phases of growth are generally difficult to obtain. Here we present a detailed method to characterize all 3 growth phases on solid media using an assay called One-cell Doubling Evaluation of Living Arrays of Yeast (ODELAY). ODELAY quantifies growth phenotypes of individual cells growing into colonies on solid media using time-lapse microscopy. This method can directly observe population heterogeneity with each growth parameter in genetically identical cells growing into colonies. This population heterogeneity offers a unique perspective for understanding genetic and epigenetic regulation, and responses to genetic and environmental perturbations. While the ODELAY method is demonstrated using yeast, it can be utilized on any colony forming microorganism that is visible by bright field microscopy

Biological treatment of acid mine drainage

Research was conducted to evaluate methods for the biological treatment of acid mine drainage (AMD). Two general approaches were evaluated. The first evaluated treatment of impounded AMD through the addition of a mixed microbial community and carbon sources appropriate for their maintenance. This approach was designed to promote sulfate reduction. Hydrogen sulfide produced by sulfate reduction can potentially react with metals in solution to form metal sulfide precipitates. The process improves pH and generally improves water quality. Several approaches were attempted to provide suitable microbial communities, carbon sources, and environmental conditions suitable for continuous microbial activity. Wood dust and typical solid waste materials were shown to support sulfate reduction, but maintenance of sulfate reduction in AMD solutions was limited. In addition to wood dust and solid waste materials, sponge substrates were used to "package" the microbial community in portable units which could be added to AMD impoundments. Tests of sulfate reduction and water quality improvement indicated that microbial communities were limited by "packaging" procedures. Sustained sulfate reduction was not obtained and water quality improvement was minimal. Several mechanisms of AMD quality improvement were evaluated or identified. Most significant was the potential for wood dust improvement of AMD quality when no biological activity was present. To provide adequate treatment of AMD, a second effort was directed to evaluation of a biologically based unit process for AMD treatment. Using an anerobic digestor which provided waste liquors high in organic acids, AMD was mixed with digestor effluent in an anaerobic reactor which maintained sulfate reduction. The end result was production of an effluent with low iron concentrations and no detectable heavy metals with a pH in the range of 6.5 to 8.5. The utility of a pilot plant design incorporating anaerobic digestion, sulfate reduction, aeration, and final clarification and settling was demonstrated. Useful outcomes of the proposed process were the production of metal precipitates in a form which is easily dewatered and potentially valuable, and the production of organic material (from the digestor) which may be considered a useful soil amendment in site reclamation.U.S. Department of the InteriorU.S. Geological SurveyOpe

Regulators of Bacterial Cell Division: Investigations of Min Oscillation and FtsA Activity

Cytokinesis is a fundamental process that is essential for bacterial proliferation. The cytokinetic machinery in bacteria is termed the “divisome”. The divisome is a complex of proteins that forms a ring at midcell over dividing nucleoids. In order for daughter cells to form, the divisome must constrict. As constriction occurs, two new cell poles are formed, one for each daughter cell. The first step in divisome formation is the assembly of FtsZ into a Z ring. The work presented in this dissertation focuses on two proteins that regulate the Z ring: MinD, which is a part of the Min system and important for positioning of the divisome; and FtsA, involved in early and late stages of divisome formation with a speculated role in regulating its constriction and disassembly. In E. coli the Min proteins oscillate from pole-to-pole to prevent Z ring formation at the cell poles. I found that MinD oscillation becomes irregular as cell length increases, and that it starts to pause frequently at each side of the developing septum. Eventually this irregular pattern switches to a doubled, regular pattern that is maintained in newly born daughter cells. I suggest this may be the mechanism by which Min proteins are equally distributed in daughter cells. My studies of FtsA show that ATP binding is important for its function in vivo, affecting its ability to interact with FtsZ and possibly with itself and other division proteins. I also show for the first time that E. coli FtsA can hydrolyze ATP

Imaging of the spleen in malaria

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