Article Abstract:
The effect of pH on the surface charges of different species of bacteria and yeast and on clay minerals was determined. The net surface charge of some bacteria, yeasts and clay minerals reversed from negative to positive then back to negative in response to increase in pH. Charge reversals occurred with cadmium, chromium, copper, nickel and zinc, in the pH range wherein the metal changed from the divalent to monovalent hydoxylated cation. The results indicated that mechanisms of metal adsorption on inorganic surfaces may be extended to cellular surfaces, and the speciation of the metal was the determining factor rather than cell or particle speciation.
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Article Abstract:
The equilibrium adsorption and binding ofBacillus subtilis DNA on montmorillontite was determined. Maximum adsorption occured after 90 minutes of contact on the clay, with maximum binding occuring at pH 1.0. The bound DNA was capable of transforming competent recipient cells,with maximum transformation occuring at 37 degrees celsius. In addition, the bound DNA was protected from degradation by DNase. These results suggest that cryptic genes may be maintained in the environment through protective binding to clay particles.
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Article Abstract:
Transgenic organisms which contain Bacillus thuringiensis genes produces insecticidal toxins and not the inactive protoxins formed by the Bacillus subspecies. These toxins accumulate in the soil and persist for a long time if they bind themselves to the soil particles. Studies show that these toxins are harmful to the larvae of the tobacco hornworm and the Colorado potato beetle and the toxicity increases by adsorption and binding to the soil particles.
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