Sorption microbial cells

Lebeau et al. (2002) investigated the sorption of cadmium by viable microbial cells that were free or immobilized in alginate beads by incubating the bacteria in a liquid soil extract medium at pH 5 7 and Cd concentrations of 1 to 10 mg L-1. The percentage of Cd biosorbed reached a maximum (69%) at low Cd concentrations and neutral pH. Thus, the effectiveness of bacteria, inoculated into metal-contaminated soils, would largely depend on the concentration of the metal and its distribution between the biomass and the medium. 

Lead,J.R., Elamilton-Taylor, J. and Davison, W. (1998) The effect of sequential extractions of suspended particulate matter on trace metal sorption and microbial cell stability. Sci. Total Environ., 209, 193. 

Sorption of microbial cells is selective but there is no obvious relation between Gram-staining characteristics and attachment, in Fig. 7.41, bacterial cells are shown adsorbing onto larger solid particles (a) or free in suspension (b) (c) illustrates the opposite effect -small particles are shown adsorbed onto bacterial cells. The bacterial cells are adsorbed onto flocculated particles in (d), onto solid surfaces in (e) (f)-(i) show the more complicated behaviour of bacterial forms with coats, cilia and flagella. The adsorption affects growth partly by masking the cell surface and... 

Water sorption, viable cell count of Rhizopus japonicum, relative mobile protons and deuterons and T2 relaxation times for freeze-dried xanthan and locust bean gum gels. (Source From Vittadini, E., Dickinson, L.C., and Chinachoti, P. NMR water mobility in xanthan and locust bean gum mixtures possible explanation of microbial response. Curb. Poly., 49,261,2002. With permission.)... 

Kumagai H, Hato C, Nakamura K. CO2 sorption by microbial cells and sterilization by high pressure CO2. Biosci Biotechnol Biochem 1997 61 931-935. 

The sorption mechanism includes diffusion motion, facilitating the penetration of molecules and ions to the active surface of colloids, their release into the medium and mutual exchanges. The diffusion is manifested during the motion of ions in the electric double layer of colloids as well as during the motion of ions and molecules to the surface of plant and microbial cells. 

Sorption of microbial cells is selective and there is no obvious relation between gram-staining characteristics and attachment. 

In soil, the chances that any enzyme will retain its activity are very slim indeed, because inactivation can occur by denaturation, microbial degradation, and sorption (61,62), although it is possible that sorption may protect an enzyme from microbial degradation or chemical hydrolysis and retain its activity. The nature of most enzymes, particularly size and charge characteristics, is such that they would have very low mobility in soils, so that if a secreted enzyme is to have any effect, it must operate close to the point of secretion and its substrate must be able to diffuse to the enzyme. Secretory acid phosphatase was found to be produced in response to P-deficiency stress by epidermal cells of the main tap roots of white lupin and in the cell walls and intercellular spaces of lateral roots (63). Such apoplastic phosphatase is safe from soil but can be effective only when presented with soluble organophosphates, which are often present in the soil. solution (64). However, because the phosphatase activity in the rhizo-sphere originates from a number of sources (65), mostly microbial, and is much higher in the rhizosphere than in bulk soil (66), it seems curious that plants would have a need to secrete phosphatase at all. 

Although the above studies conducted with packed columns are important from a fundamental standpoint as they relate to the mechanisms of cell sorption to solid surfaces, in situ remediation of contaminants in subsoils requires microbial transport in well-structured soils. The presence of soil macropores that facilitate preferential water flow is well appreciated (Thomas Phillips, 1979). Sorption phenomena are less important when bacterial transport occurs through structured soils in which cells pass unimpeded through relatively large conduits (Smith et al., 1985). 

The soil is a complex structure with close interrelationship among factors that influence biodegradation of pesticides, such as the structure of the pesticide, presence of an effective, active microbial community capable of degradation, and bioavailability of the compound in space and time (sorption, moisture content, temperature, nutrients, and soil pH) to enzymes or to whole cells (Aislabie and Lloydjones, 1995). 

Besides physicochemical reactions, metals have easy access to bacterial surfaces through diffusion. Metal sorption and precipitation on bacterial surfaces are interfacial effects. Surface metal concentrations frequently exceed the stoichiometry expected per reactive chemical sites within cell walls (Beveridge, 1989 McLean et al., 2002). The sorption of metals can be so great that precipitates can be formed, and distinct minerals are eventually formed through microbial biomrneralization (i.e., the formation of minerals by microbes). 

Templeton et al. (2002a) used a combination of Pb Lm-XAFS and pXANES spectroscopy and transmission electron microscopy to show that B. cepacia causes biomineralization of Pb(II) in the form of highly insoluble pyromorphite at ( ) concentrations well below supersaturation with respect to pyromorphite. The phosphate in these minimal medium experiments is though to be provided by B. cepacia, and the pyromorphite forms on the outer cell membrane of B. cepacia. These types of studies are beginning to provide unique information on how microbial biofilms affect metal sorption processes at mineral surfaces, which is essential for understanding the transport and bioavailability of toxic metal ions in natural systems where such biofilms exist. They are also allowing quantitative evaluation of the competition between NOM (or biofilms) and the mineral substrates they coat for metal ion binding. 

PROBABLE FATE photolysis dissolved portion should undergo rapid photolysis to quinones, when released to air, may undergo direct photolysis, although adsorption can slow this process, direct photolysis is important near surface of waters half-life for reaction with photo-chemically produced hydroxyl radicals 21.49 hr oxidation oxidation by chlorine and/or ozone could account for a small portion of the dissolved compound hydrolysis not an important process volatilization probably too slow to compete with adsorption as a transport process, evaporation may be important, but limited by adsorption, half-life 43 days sorption very strong adsorption onto suspended solids is the dominant transport process, adsorption in estuarine water 3 pg/L, 71% adsorbed on particles after 3 hr, after 3hr incubation in natural seawater, 75% of 2 pg/L adsorbed to suspended aggregates of dead photoplankton cells and bacteria biological processes bioaccumulation is short-term metabolization and microbial degradation are principal fates... 

Mansfeld F (1994) Effectiveness of ion vapor-deposited aluminum as a primer for epoxy and urethane topcoats. Corrosion 50 609-612 Mansfeld F (1995) Use of dectrochemical impedance spectroscopy for the study of corrosion by polymer coatings. J Appl Electrochem 25 187-202 Margulis L (1981) The endosymbiotic theory. In Margulis L (ed) Symbiosis in cell evolution. W. H. Freeman, San Francisco, pp 1-14 Marshall KC, Stout R, Mitchell R (1971) Mechanism of the initial events in the sorption of marine bacteria to surfiices. J Gen Microbiol 68 337-348 Marshall KC (1976) Solid-liquid and solid-gas interfaces. In Marshall KC (ed) Interfaces in microbial ecology. Harvard University Press, Cambridge, pp 27—52... 

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