Influence of H⁺ and Calcium Ions on Surface Functional Groups of Synechococcus PCC 7942 Cells

Abstract

The chemistry of the surface functional groups of picocyanobacteria Synechococcus PCC 7942 cells was examined as a function of H+ and calcium concentrations. Titration experiments, infrared spectroscopy, biosorption experiments, and chemical modeling were used to gain insight into the mechanisms of biosorption. The pKa and concentration of active sites on the cell wall were clarified with the aid of potentiometric titration. Modeling calculations and infrared spectra are consistent with pKa's values of 4.3, 5.2, 6.9, 9.1, and 10.0 and a total concentration of 7.8 x 10(-4) mol g(-1). Spectral analysis of an aqueous cellular suspension revealed a presence of carboxyl, amide, phosphate, hydroxyl, and carbohydrate moieties. Correspondence between spectral data and potentiometric titration curves supported the hypothesis that carboxylate groups and phosphodiester groups mediate calcium adsorption to bacterial cells. This process is strongly pH dependent. In the second part of the experimental work, Synechococcus cells were suspended in the presence of different calcium concentrations. Mechanistic modeling demonstrated that the calcium adsorption phenomenon can be described taking into account only two mechanisms: ion exchange and complexation.

Surface charge and zeta-potential of metabolically active and dead cyanobacteria

“…cyanobacteria in Figs. 1 and 2, is in good agreement with surface charge excess data reported previously for different Gram− and Gram+ heterotrophic bacteria [28,38,39]. Note, however, there is essentially constant from pH 3.1 to 8.5.…”

Modification of exopolysaccharide composition and production by three cyanobacterial isolates under salt stress

“…And only recently, there has been an interest in metal adsorption processes by these microorganisms (Dittrich and Sibler 2006;Pokrovsky and Kompantseva 2007) and their participation in biomineral formation (Dittrich et al 2003;Yee et al 2004;Obst et al 2006). In recent years, owing to the increasing interest in the exploitation of microorganisms for the production of valuable polysaccharides for various industrial applications, the attention towards the polysaccharide-producing cyanobacteria greatly increased, in particular, towards the strains that possess abundant capsule or slime and also release large amounts of released polysaccharides (De Philippis et al 2001).…”

Cell surface characterisation of Microcystis aeruginosa and Chlorella vulgaris

“…Invoking a three-site model provides sufficient approximation to describe the proton binding [17,44]. The four or five site models enabled also a correct description of proton binding but it is not possible to assign to the supplementary sites, a chemical function different from the ones considered in the three-site model [15,17,22].…”

“…The concentrations and characteristics of proton-active carboxylic, phosphoric, phosphodiester, hydroxyl and amine functional groups on cell surfaces play a major role in surface binding capacity, biomineralisation, bacterial adhesion and biofilm formation [13,[16][17][18][19][20][21]. Recent studies led to the identification of the protonactive functional groups on bacterial and algal surfaces and the determination of thermodynamic metal binding constants [22][23][24]. Beveridge and Murray [25] and Burnett et al [26] showed that deprotonation of functional groups conferred electrostatic charge to the cell periphery and gave the cell wall anionic characteristics and thus metal binding ability [27].…”