Immunoblot analysis of the filtrates for the detection of a cytoplasmic marker, cAMP receptor protein. The whole cell protein preparations of V. cholerae crp+ strain (lane 1), V. cholerae crp- strain (lane 2) and A. actinomycetemcomitans D7SS (lane 3) were used as controls in the immunoblot with antibodies against V. cholerae cAMP receptor protein. Serum filtrates (8 h): D7SS (lane 4), D7SS-p (lane 5) and No bacteria control (lane 6). Broth filtrates (24 h): D7SS (lane 7), D7SS-p (lane 8) and No bacteria control (lane 9). Detection of cAMP receptor protein from precipitated filtrates of lysed (lane 10) and unlysed D7SS cells (lane 11) incubated in the inserts containing broth for 8 h.