FIG. 4.

Standard curve construction. (a) DNA extracted from 10¹⁰ C. proteoclasticum cells ml⁻¹ was serially diluted and coamplified with a 10⁶ dilution of the internal control. The results are expressed as C. proteoclasticum cell equivalents based on the amount of DNA extracted per cell. (b) Ratios of the intensities of internal control to target DNA were quantitated by scanning densitometry of negative images of Polaroid photographs of ethidium bromide-stained gels.