Change of Extracellular Polymeric Substances Composition of Thiobacillus thioparus in Presence of Sulfur and Steel

Abstract

The process of microbially influenced corrosion (MIC) of metallic underground constructions is often related with biofilm formation and metabolic activity of sulfur cycle bacteria. The extracellular polymeric substances (EPS) produced by these bacteria in biofilms on metallic surfaces establish the interfacial reaction space in which relevant corrosion processes occur. The EPS composition of the sulfur oxidizing bacterium Thiobacillus thioparus DSM 505 varies according to growth conditions. Presence of elemental sulfur and mild steel are demonstrated here as stimulants for variation of the EPS composition. The distribution of sugar moieties in the EPS of planktonic and biofilm grown cells of Thiobacillus thioparus DSM 505 was observed by fluorescently labeled lectin binding assays. The strongest signal was found with the PWM lectin (Pokeweed, Phytolacca americana) specific for Poly- N-Acetylglucosamine (PNAG). Cell associated proteins, visualized by Thiazine Red staining, were observed in the planktonic growth mode. Low amounts of EPS proteins from planktonic were detected. The observed influence of elemental sulfur and mild steel on the EPS composition in biofilm forming cells can be suggested to have a pivotal role in interfacial processes such as (bio) corrosion. Understanding factors that mediate changes in the composition and surface associated structural features of EPS as a consequence of working materials may help to develop a new strategy for biocorrosion prevention.