Lakes bacterial activity

Because of the high area of solid surfaces covered with biofilms, these biofilms dominate the heterotrophic metabolism in many aquatic ecosystems. In streams, rivers, and shallow lakes, bacterial activity in epilithic and epiphytic biofilms may be several times higher on an areal basis than the activity of free living bacteria. By the differential use of specific DOM fractions, biofilm bacteria influence the biogeochemical composition of DOM in these ecosystems. Biofilms thus can control biogeochemical fluxes of DOM and are important sinks of organic matter. 

PEST. This code ( 3) was developed within the framework of Rensselaer Polytechnic Institute s CLEAN (Comprehensive Lake Ecosystem Analyzer) model. It includes highly elaborated algorithms for biological phenomena, as described in this volume (44). For example, biotransformation is represented via second-order equations in bacterial population density (Equation 5) in the other codes described in this section PEST adds to this effects of pH and dissolved oxygen on bacterial activity, plus equations for metabolism in higher organisms. PEST allows for up to 16 compartments (plants, animals, etc.), but does not include any spatially resolved computations or transport processes other than volatilization. 

Lake, M. W., Wuebbens, M. M., Rajagopalan, K. V., and Sghindelin, H. Mechanism of ubiquitin activation revealed by the structure of a bacterial MoeB-MoaD complex. Nature 2001, 434, 325-329. 

We determined the net formation rates in discrete samples at several depths in the water column, with and without filtration, using waters from several lakes. We also investigated the decay processes, in the dark, for whole lake waters, lake waters filtered through varying mesh size filters, and in pure bacterial cultures. These results added to our understanding of the processes responsible for the observed distribution of H202. Our current research activities (18) are reviewed and synthesized in this chapter. 

This bacterial production occurs in the pore fluids of sediments and in stagnant basins (seas, lakes, rivers and fiords). At the interface between anoxic and oxic waters the H2S can be oxidized. This oxidation is frequently coupled to changes in the redox state of metals (1.2) and non-metals (2). Another major interest in the H-jS system comes from an attempt to understand the authigenic production of sulfide minerals as a result of biological or submarine hydrothermal activity and the transformation and disappearance of these minerals due to oxidation (4). For example, hydrothermally produced H2S can react with iron to form pyrite, the overall reaction given by... 

A particular interest of environmental chemists has been the interaction of inorganic and organic matter with bottom sediments in lakes, rivers, and oceans. These surface sediments are not simply unreactive sinks for pollutants but can be studied quantitatively in terms of how many specific chemicals are bonded to a certain amount of sediment, which in turn is influenced by whether the conditions are oxidizing or reducing. Chemists can then study the bioavaU-ability of contaminants in sediments. Furthermore, environmental chemists have studied dissolution and precipitation, discovering that the rates of these processes depend on what happens in surface sediments. Using such techniques as scanning polarization force microscopy, they have been able to quantify pollutant immobilization and bacterial attachment on surface sediments. Specifically, they have used these methods to understand the concentrations and activities of heavy metals in aquatic sediments. 

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