Thermophilic mineral-microbe interfacial environments explored: Insights into the building blocks of the Metallosphaera hakonensis biofilm

摘要

This study provides the first insight into the extraction and characterisation of extracellular polymericsubstances (EPS) and visualisation of EPS interfacial environments of Metallosphaera hakonensis undermineral bioleach conditions. Three EPS architectural motifs for growth of M. hakonensis on chalcopyritewith different mineral-microbe contact and fluid flow were observed in situ using fluorescent-labelled lectinprobes and confocal scanning laser microscopy (CSLM). A methodology to extract and chemicallycharacterise EPS from M. hakonensis was developed, allowing identification and characterization ofcolloidal, loosely bound and capsular (bound) EPS. Cells grown on chalcopyrite yielded the greatest levels ofEPS (15.6 ± 1.8 mg per 1 × 10~(10) cells), followed by cells grown on sulphur (9.5 ± 0.3 mg per 1 × 10~(10) cells)and ferrous sulphate (7.4 ±1.9 mg per 1 × 10~(10) cells), respectively. The EPS consisted of sugars, proteins,uronic acids and nucleic acid, with the relative composition depending on the substrate and localisation ofthe EPS. Results highlight differences in the mineral-microbial-EPS interfacial environments, created as afunction of inoculation conditions, energy source and configuration of the leaching environment e.g. tankand heap bioleach systems.