Colony Immunoblotting Assay for Detection of Bacterial Cell-surface or Extracellular Proteins

Abstract

This simple protocol describes how to detect antigens from agar-grown bacterial colonies transferred to nitrocellulose using specific antibodies. The protocol is well suitable for detection of bacterial proteins exposed on the cell surface or secreted to the extracellular space and it can be modified also for detection of intracellular proteins. The assay can distinguish bacterial clones with different expression rates (high, medium and low) from colonies that do not express target protein. We used this assay for screening of Mat fimbriae-producing Escherichia coli mutants obtained by mini-Tn5 transposon mutagenesis and immunomagnetic separation (Lehti et al., 2013).