The membrane-induced proton motive force influences the metal binding ability of Bacillus subtilis cell walls

Abstract

Bacillus subtilis 168 is a gram-positive bacterium whose cell wall contains the highly electronegative polymers peptidoglycan (chemotype Aly) and glycerol-based teichoic acid to produce a surface with a net negative charge with high metal binding capacity. During metabolism, a membrane-induced proton motive force continuously pumps protons into the wall fabric. As a result, a competition between protons and metal ions for anionic wall sites occurs, and less metal is bound in living cells than in nonliving cells or those in which the plasma membrane has been uncoupled. This was shown by using two metallic ions, UO22' and SC3+, on control cells, cells uncoupled with either carbonyl cyanide m-chlorophenylhydrazone or NaN3, or cells killed by gamma radiation. Transmission electron microscopy, energy-dispersive X-ray spectroscopy, and inductively coupled plasma atomic-emission spectroscopy showed that more metal was retained in the walls of nonliving cells and those with deenergized membranes than in their living counterparts.

Nickel partitioning in biogenic and abiogenic ferrihydrite: The influence of silica and implications for ancient environments

“…As metabolically active phototrophic Fe(II)-oxidizing bacteria were shown not to encrust, and since we observed only a few encrusted cells, we believe that a small fraction of dead cells in our cultures were not able to actively maintain their acidic microenvironment, thereby facilitating mineral precipitation on the cell wall. This is consistent with other studies that have shown live, dormant, moribund and dead cells differing in their mineralization behavior (Urrutia et al, 1992;Toporski et al, 2002). In support of this, dead cells show an increased availability of functional groups capable of metal binding as a result of cellular degradation (Ferris et al, 1988).…”

Specific jarosite biomineralization by Purpureocillium lilacinum, an acidophilic fungi isolated from Río Tinto

“…This is a passive process that can be carried out by living and dead fungal cells (Sterflinger, 2000) and is based on the ability of microorganism surfaces to bind ions (e.g. Beveridge and Murray, 1976;Urrutia et al, 1992). The charged cell walls as well as the reactive groups of the EPS provide active interfacial sites for adsorption and complexation of dissolved aqueous metal species, inducing the nucleation and precipitation of minerals by reducing the activation energy barriers (e.g.…”

“…In addition to growth conditions, the resultant mineral may depend on the nature of the cell surface, the cellular microenviroment and on the presence of certain reactive anions in the cell walls. Since the electrostatic interactions are metabolically independent in BIM processes, biomineralization can occur on cells that are not viable (Beveridge and Murray, 1976;Urrutia et al, 1992). In this study, we report for the first time the specific generation of (hydronium)-jarosite by an acidic fungal isolate, Purpureocillium lilacinum.…”

Rapid in situ silicification of microbes at Loburu hot springs, Lake Bogoria, Kenya Rift Valley

“…The most favourable conditions for rapid silici®cation, however, may develop soon after the organism dies. Metabolically active bacteria, for example, have a lower capacity for binding metal ions than inactive or dead cells because protons released from the cell during respiration occupy some negatively charged sites on the cell wall (Urrutia et al, 1992). Limited cell decay may increase the number of OH ± sites available for silici®cation (Ferris et al, 1988).…”