The Effect of Ionic Strength on the Adsorption of H+, Cd2+, Pb2+, and Cu2+byBacillus subtilisandBacillus licheniformis:A Surface Complexation Model
✍ Scribed by Christopher J. Daughney; Jeremy B. Fein
- Publisher
- Elsevier Science
- Year
- 1998
- Tongue
- English
- Weight
- 433 KB
- Volume
- 198
- Category
- Article
- ISSN
- 0021-9797
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✦ Synopsis
metals may play an important role in the subsurface transport
To quantify metal adsorption onto bacterial surfaces, recent of metals occurring as groundwater contaminants ( 19), the studies have applied surface complexation theory to model the fossilization of microorganisms (20), and the accumulation specific chemical and electrostatic interactions occurring at the of metal deposits ( 21). If such geochemical processes are solution-cell wall interface. However, to date, the effect of ionic to be quantified, a suitable model describing metal-bacteria strength on these interactions has not been investigated. In this interactions in natural environments must be developed.
study, we perform acid-base titrations of suspensions containing
Recent research indicates that the binding of protons and
Bacillus subtilis or Bacillus licheniformis in 0.01 or 0.1 M NaNO 3 , metal ions onto bacterial surfaces can be effectively deand we evaluate the constant capacitance and basic Stern doublelayer models for their ability to describe ionic-strength-dependent scribed in terms of surface complexation, within the framebehavior. The constant capacitance model provides the best dework of equilibrium thermodynamics (15,17,18,22). scription of the experimental data. The constant capacitance Acid-base titrations of bacterial suspensions permit the demodel parameters vary between independently grown bacterial termination of the absolute concentrations and deprotonation cultures, possibly due to cell wall variation arising from genetic constants of specific proton-active surface sites on the cell exchange during reproduction. We perform metal-B. subtilis and walls. Experimental studies of isolated systems containing metal-B. licheniformis adsorption experiments using Cd, Pb, and a single metal and a single species of bacteria permit the Cu, and we solve for stability constants describing metal adsorpdetermination of site-specific thermodynamic stability contion onto distinct functional groups on the bacterial cell walls. We stants describing the formation of metal-bacteria surface find that these stability constants vary substantially but systematically between the two bacterial species at the two different ionic complexes. For example, Fein et al. (17) suggest that the strengths. ᭧ 1998 Academic Press cell walls of Bacillus subtilis display carboxyl, phosphate,