Transcriptomic studies of capsular polysaccharide export systems involved in biofilm formation by Acidithiobacillus ferrooxidans

摘要

Bioleaching is the dissolution of metal sulfides, such as pyrite (FeS2) by bacterial oxidation processes. Selective attachment and biofilm formation on sulfidic mineral surfaces by Acidithiobacillus ferrooxidans is important for this process. Uronic acid residues present in the extracellular polymeric substances ( EPS) bind ferric ions. These bound ferric ions inherent in the EPS mediate attachment and also serve as the main oxidative agents for pyrite dissolution. Consequently, the EPS-matrix is a reaction space, coupling the bacterial respiratory chain with the chemical oxidation of pyrite. Bioinformatic analysis of At. ferrooxidans complete genome sequence revealed the presence of at least five gene clusters containing homologous genes of two different capsular polysaccharide export systems to those capsular polysaccharide ( CPS) biosynthesis and export systems described in E. coli and other Gramnegative bacteria. The presence of two genes homologous to wza, encoding an outer membrane polysaccharide export ( OPX) protein, suggests that at least two different types of polysaccharides could be exported. In this paper the expression patterns of cells grown on different energy sources were compared using quantitative RT-PCR of the respective RNA. Results show substrate and cell-population specific differences in gene expression patterns.