In situ enzyme immunodetection of surface or intracellular bacterial antigens using nitrocellulose sheets

We describe an immunological method which allows the in situ colorimetric detection of translated DNA fragments in bacteria. In the absence of lysis only cell surface proteins are detected. For cytoplasmic proteins, lysis is required. The procedure comprises the following steps: bacteria are lysed, the proteins are transferred onto a disc of nitrocellulose sheet, the remaining protein sites are blocked, the disc is successively soaked in a solution of antibodies specific for the protein to be detected and in a solution of peroxidase-labelled anti-IgG antibody solution. Finally, the immune complexes are made visible by enzyme substrate incubation. We describe the application of this method to the detection of the LamB protein, the LacZ protein, and a LamB-polio VP1 chimera translated from cloned DNA fragment in E. coli.