Shewanella oneidensis is of particular interest for research because of its unique ability to use a variety of metals as final respiratory electron acceptors and reduce them into insoluble oxides. A collection of monoclonal antibodies (mAbs) that were prepared towards Escherichia coli RNA polymerase (RNAP) was tested for reactivity with proteins extracted from S. oneidensis. Two polyol-responsive monoclonal antibodies (PR-mAbs) were used to purify RNA polymerase from S. oneidensis using immunoaffinity purification techniques. A collection of mAbs towards E. coli sigma subunits was also examined for cross-reactivity with S. oneidensis proteins. Reactions were identified with mAbs to E. coli sigma(70) and sigma(54). These mAbs will be useful tools for immunoaffinity purifying and studying the transcriptional machinery of S. oneidensis.