Influence of Growth Substrate and Attachment Substratum on EPS and Biofilm Formation by <i>Acidithiobacillus ferrooxidans</i>

Abstract

Extracellular polymeric substances (EPS) of Acidithiobacillus ferrooxidans and other leaching microorganisms mediate the attachment of cells to pyrite and other minerals. They also play a pivotal role in indirect leaching of base and precious metals via the contact mechanism. The aim of this study is to get more insight on the influence of the growth substrates iron(II) ions, pyrite, chalcopyrite and elemental sulfur on EPS formation, attachment and biofilm formation. The synthesis of EPS by cells of A. ferrooxidans strain A2 is strongely influenced by the growth substrate or attachment substratum of the cells. Cells grown with soluble iron(II) ions generally generate less EPS than cells grown with solid pyrite, chalcopyrite or elemental sulfur. Planktonic cells grown in the presence of solid substrate produce two to four times more EPS than iron(II) ion grown cells. With sessile cells, this factor is further increased to 50 to 240 depending on the specific substrate. The EPS of all the differently grown planktonic and sessile cells of A. ferrooxidans strain A2 contained neutral sugars, fatty acids, uronic acids, proteins and metal ions. The composition of these compounds varied with the growth substrate and type (planktonic or sessile). The attachment behavior of cells of A. ferrooxidans strain A2 also differed with the substrate of the pre-culture. Cells grown on iron(II) ions, pyrite or chalcopyrite attached rapidly to pyrite and chalcopyrite, while attachment to elemental sulfur was poor. On the contrary, sulfur grown cells attached well to elemental sulfur but weakly to pyrite and chalcopyrite. Attachment of EPS-free cells to all substrates was also diminished. Cells of A. ferrooxidans strain A2 cover mineral surfaces with a dense biofilm after a few days of cultivation, as visualized by fluorescence microscopy and AFM. Large amounts of EPS are formed, which eventually cover the cells and the mineral surface. Even after a few weeks of cultivation the biofilm remained monolayered on all substrates.

Evolution of biofilms during the colonization process of pyrite by Acidithiobacillus thiooxidans

“…It has been demonstrated that the nature and quantity of EPS produced and secreted by bioleaching cells is strongly influenced by the culture conditions and the electrochemical characteristics of the substratum (Donlan 2002), and that freeliving (planktonic) cells produce less EPS than cell attached to a mineral (Harneit and Sand 2007); also, that the main EPS produced by bioleaching microorganisms grown on pyrite are neutral polysaccharides (glucose, rhammose, fucose, xylose, and mannose), lipids or saturated fatty acids, and lipopolysaccharides (Gehrke et al 1998).…”

Effects of Single and Mixed Energy Sources on Intracellular Nanoparticles Synthesized by Acidithiobacillus ferrooxidans

“…As shown in Figure 1, in medium 1 # , the logarithmic phase of the bacteria started at 12 h and ended at 48 h with a peak cell density of 8.0 × 10 7 cells/mL. There was a slight decrease in bacteria density in the 2 # , 3 # , and 4 # media during the initial growth period, which was attributed to the adsorption of a free population on the surface of elemental sulphur [47,48]. The lag phase of bacteria in the medium with added elemental sulphur was longer than that in the medium using ferrous iron as the sole energy source because of a period of adaptation in the ferrous grown culture to a mixed substrate and sulphur-only environment.…”

A hybrid model for biofilm growth on a deformable substratum

“…A lthough the influence of different properties of the substratum on the formation and evolution of biofilms has been extensively studied by many investigators, [1][2][3][4][5][6][7][8][9] the effect of the deformability of a deformable substratum has not received wide attention except in the recent study by Martin et al, [10] who showed that the geometry of the membrane in Membrane Biofilm Reactors (MBfR) significantly affects the growth rate of the biofilm and hence can be used to enhance the efficiency of the membrane. Bol and Albero [11] developed a model for biological systems growing in an inhomogeneous manner thereby generating residual stresses even when growth rates and material properties are homogeneous.…”