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 mlÿ1 for cell-walled and 103 viable cells mlÿ1 for L-forms. This was equivalent to 12 mg protein
mlÿ1 and 96 ng protein mlÿ1 , respectively The speci®city of the antiserum was further investigated by testing a selection of Bacillus strains and an unidenti®ed Bacillus isolate cultured from compost samples (Fig. 2). Laboratory strains of B. brevis, B. cereus and B. licheniformis were detected at approx. 106 cells mlÿ1 and the compost