Interactions of exopolymers produced by sulphate-reducing bacteria with metal ions

The aim of this study was to determine the effect of metal species such as Cr, Ni and Mo on growth and on the production of exopolymeric substances (EPS) in batch cultures of two strains of marine sulphate-reducing bacteria (SRB) isolated from corrosion failures in Portsmouth (UK) and Indonesia. In addition, the ability of EPS released into the liquid phase of the bacterial growth media to complex Cr, Ni and Mo, was investigated using atomic absorption spectroscopy. Results demonstrated that metals influence both SRB growth and exopolymer production and that the effect of the metal species on bacterial metabolism depends on the type of SRB. The presence of Cr, Ni and Mo was detected in EPS recovered from 3 day old SRB cultures. Although concentrations of these elements in exopolymers varied with metal species and with the SRB isolate, levels of Mo associated with EPS were significantly higher than the measured amount of Cr or Ni, regardless of the bacterial isolate.