Direct and indirect impact of the bacterial strain Pseudomonas aeruginosa on the dissolution of synthetic Fe(III)- and Fe(II)-bearing basaltic glasses

Abstract

Abstract This study investigates the direct and indirect bacterial contributions that influence the dissolution of basaltic glass. In this regard, three different types of glasses – with or without Fe, in the reduced Fe(II) or oxidized Fe(III) states – were prepared on the basis of a simplified basaltic glass composition. In order to prevent the direct contact between the glasses and the model siderophore-producing strain Pseudomonas aeruginosa, the glass samples were isolated in dialysis bags and immersed at 25\u202f°C and pH\u202f6.5 in bacterial cultures. Throughout the dissolution experiments, the following parameters were monitored: determination of bacterial growth, quantification of siderophore (i.e. pyoverdine) production, microscopic observation of the glass surface and determination of dissolution kinetics. Isolating the glass from the bacterial suspension only triggered the biosynthesis of siderophores in the Fe(III)-bearing glass dissolution experiments. Siderophores were produced in the presence of Fe(II)-bearing and Fe-free glass, independently on the experimental setup. The siderophore production appeared to be either continuous in the absence of Fe (glass-free control, Fe-free glass dissolution experiments) or stopped as soon as the bacteria entered their stationary phase when an Fe source was present (Fe(II) and Fe(III)-bearing glass dissolution experiments). The increase in the dissolution rates of each glass was correlated to the complex stability constants of the siderophore with the metallic cations in presence (KFe2+