Both the parental, cell-walled form and L-form were detected in the ELISA (Fig. 1), although there was a clear difference in the extent to which each cell type was recognized.
Figure 1 shows that the limits of detection were
approx. 107 viable cells ml ÿ1 for cell-walled and 103 viable cells ml ÿ1 for L-forms. This was equivalent to 12 mg protein ml ÿ1 and 96 ng protein ml ÿ1, respectively. The specificity of the antiserum was further investigated by testing a selection of Bacillus strains and an unidentified Bacillus isolate cultured from compost samples (Fig. 2). Laboratory strains of B. brevis, B. cereus and B. licheniformis were detected at approx. 106 cells ml ÿ1 and the compost