Interface, microbes

Hamilton SK, Bunn SE, Thoms MC et al (2005) Persistence of aquatic refugia between flow pulses in a dryland river system (Cooper Creek, Australia). Lirrmol Oceanogr 50 743-754 Bernal S, Butturini A, Sabater E (2002) Variability of DOC and nitrate responses to storms in a small Mediterranean forested catchment. Hydrol Earth Syst Sci 6 1031-1041 Romani AM, Vazquez E, Butturini A (2006) Microbial availability and size fractionation of dissolved organic carbon after drought in an intermittent stream biogeochemical link across the Stream-Riparian interface. Microb Ecol 52 501-512... 

Environmental chemicals occur as pure liquid or solid compounds, dissolved in water or in nonaqueous liquids, volatilised in gases, dissolved in solids (absorbed) or bound to interfaces (adsorbed). Figure 5 gives a schematic view of the different physical states at which substrates are taken up by microbial cells. There is a consensus that water-dissolved chemicals are available to microbes. This is obvious for readily soluble chemicals, but there is also clear evidence for microbial uptake of the small dissolved fractions of poorly water soluble compounds. Rogoff already had shown in 1962 that bacteria take up phenanthrene from aqueous solution [55], In the intervening time many other researchers have made the same observation with various combinations of microorganisms and poorly soluble compounds [14,56,57]. 

Microbes were frequently found to synthesise surface-active molecules in order to mobilise hydrophobic organic substrates. These biosurfactants, which are either excreted by the producing organisms or remain bound to their cell surfaces, are composed of a hydrophilic part making them soluble in water and a lipophilic part making them accumulate at interfaces. With respect to their physical effects, one can distinguish two types of biosurfactants firstly, molecules that drastically reduce the surface and interfacial tensions of gas-liquid, liquid-liquid and liquid-solid systems, and, secondly, compounds that stabilise emulsions of nonaqueous phase liquids in water, often also referred to as bioemulsifiers. The former molecules are typically low-molar-mass... 

It is often difficult to predict the fate of a pollutant in an interfacial microenvironment because the interactions between the microbial, chemical, and physical components of the environment are still not well understood. The total microbial activity at aqueous-solid phase interfaces depends on a variety of factors, such as numbers of microbes, available nutrients, environmental conditions, and pollutant chemical structure. The impact of some of the most important factors affecting microbial activity, with the implicit understanding that microbial activity can be inhibited by any one of these factors, will be discussed in the present sections. 

Filer JM, Mojzsis SJ, Arrhenius G (1997) Carbon isotope evidence for early life discussion. Nature 386 665 Emerson D (2000) Microbial oxidation of Ee(II) and Mn(II) at circumneutral pH. In Environmental metal-microbe interactions. Lovley DR (ed) ASM Press, Washington DC, p 31-52 Ewers WE (1983) Chemical factors in the deposition and diagenesis of banded iron-formation. In Iron formations facts and problems. Trendall AF, Morris RC (eds) Elsevier, Amsterdam, p 491-512 Farley KJ, Dzombak DA, Morel FMM (1985) A surface precipitation model for the sorption of cations on metal oxides. J Colloid Interface Sci 106 226-242... 

Sharma, M., Sharma, N.N. and Bhalla, T.C., Hydroxynitrile lyases at the interface of biology and chemistry. Enzyme Microb. Technol., 2005, 37, 279. 

In Chapter 4, we saw how conservative chemicals are used to trace the pathway and rates of water motion in the ocean. True conservative behavior is exhibited by a relatively small number of chemicals, such as the major ions and, hence, salinity. In contrast, most of the minor and trace elements display nonconservative behavior because they readily undergo chemical reactions under the environmental conditions found in seawater. The rates of these reactions are enhanced by the involvement of marine organisms, particularly microorganisms, as their enzymes serve as catalysts. Rates are also enhanced at particle interfaces for several reasons. First, microbes tend to have higher growth rates on particle surfaces. Second, the solution in direct contact with the particles tends to be highly enriched in reactants, thereby increasing reaction probabilities. Third, adsorption of solutes onto particle surfaces can create fevorable spatial orientations between reactants that also increases reaction probabilities. 

The resident microbes within the mouth readily form biofilms on teeth. A biofilm consists of a population of bacteria coexisting in an orderly structure at the interface of a solid and a liquid [14] and, within a biofilm, bacteria living in colonies encapsulated in a matrix of extracellular polymer. Oral biofilms are known to vary extensively in structure throughout the colony, with regions of densely packed microorganisms surrounded by open water channels. Each type of bacteria exists in reasonably defined environments which are influenced by surrounding cells, distance from the outer surface and local structure, all of which influence availability of nutrients and ambient pH. 

Jackson, A.O. and Taylor, C.B., Plant-microbe interactions life and death at the interface, Plant Cell, 8, 1651, 1996. 

Microbes residing in sediment beneath oceans and lakes derive energy by oxidizing organic matter. 02 is available as the oxidant at the sediment-water interface, but it is depleted within millimeters below the interface. Nitrate and Fe(III) oxidants are available in the first few centimeters of sediment. When they are exhausted, sulfate becomes the predominant oxidant for a distance of 1 m. The sulfate reduction product, HS-, is released in millimolar concentrations into solution in the sediment pores. 

Although this compound is not a traditional coupling agent, it does provide for a biologically effective interface between microbes and a variety of surfaces, and... 

S. Colombie, A. Gaunand, and B. Lindet, Lysozyme inactivation under mechanical stirring effect of physical and molecular interfaces, Enz. Microb. Technol. 2001, 28, 820-826. 

Perry, L. G, Alford, E. R., Horiuchi, J., Paschke, M. W., and Vivanco, J. M. (2007). Chemical signals in the rhizosphere Root-root and root-microbe communication. In The Rhizosphere Biochemistry and Organic Substances at the Soil-Plant Interface, 2nd edition, Pinton, R., Varanini, Z., and Nannipieri, P., eds., CRC Press, Boca Raton, FL, pp. 297-330. 

The biodegradation of crude oils in their reservoirs is well documented (M, 22). It occurs in the presence of meteoric water which supplies dissolved oxygen and nutrients including phosphate and fixed nitrogen. Microenvironments may exist in which aerobic and anaerobic activities occur in close proximity so that intermediates of aerobic metabolism may become substrates for anaerobic bacteria. In reservoirs, microbes are most active at the oil-water interface and at temperatures between about 20° and 60 to 75°C. 

Microbial mats and biofilms, defined as surface layers of microbes entrained in a matrix of extracellular polymeric substances (EPS) (Characklis and Marshall, 1989), are also important in changing the surface texture and erodibility of sediments in estuaries (de Beer and Kiihl, 2001). The EPS are primarily composed of cellular-derived polysaccharides, polyuronic acids, proteins, nucleic acids, and lipids (Decho and Lopez, 1993 Schmidt and Ahring, 1994). The EPS can serve as a cementing agent for surface sediment particles, thereby affecting the erodibility of sediments as well as the flux of dissolved constituents across the sediment-water interface (de Beer and Kiihl, 2001). 

Resistance near the solid-liquid interface This resistance can be significant because of the small relative velocity differences resulting from the low density difference between the continuous aqueous medium and a dispersed phase such as microbes, gel-entrapped enzymes, etc. 

Because NTR links the reduced and oxidized sides of the N cycle, it can be considered a central process that provides substrate to microbes that employ nitrate or nitrite as oxidant (see Chapter 5 by Ward, this volume Fig. 19.1, arrow 4). Like NH4, the products of NTR, N02, and NOs , may experience one of several possible fates, including (1) flux from the sediment, (2) assimilation within the sediment or at the sediment—water interface, or (3) reduction by one of three possible dissimilatory pathways DNF, dissimilatory nitrate reduction to ammonium (DNRA), or ANAM (Fig. 19.1, arrows 5, 6, and 7 Fig. 19.2). Uptake of NO by... 

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

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