Biofilm formation by sulphate reducing bacteria on different metals and its prospective role in titanium corrosion

This study describes the biofilm formation by sulphate reducing bacteria (SRB) on different materials, which has implications for the biomedical, pharmaceutical, food and chemical process industries. SRB was chosen as a model organism being an anaerobic bacterium. Biofilm formation on different materials and corrosion of titanium by SRB were monitored with time using confocal laser scanning microscopy and fluorescent FISH probes were used to authenticate the SRB strain. The thickness of the mono-culture SRB biofilm has ranged from 4-24 µm during the period 12-84 hrs, however, the maximum biofilm thickness (24 µm) was recorded after 60 hrs of growth. Planktonic growth of the SRB strain showed a log phase up to 48 hrs and the sulphide production ranged from 2 to 14 mg l-1. For a comparative account, the SRB biofilm formation on copper was chosen as a positive control. Finally, the putative role of extracellular electron transfer by SRB in the biocorrosion process and the plausible mechanism of pitting corrosion of titanium are described in detail.