FIG. 2.

Micro-RDA sensitivity test. Different amounts, ranging from 1 copy per cell up to 100 copies per cell, of a known RNA species (MS2 RNA) was mixed with total RNA of S. aureus. In the subsequent micro-RDA, this mixture was used as the tester and total S. aureus RNA was used as the driver. DP 3 was electrophoresed through a 2% agarose gel and stained with ethidium bromide. Fragments typical of the MS2 amplicon could be detected in the spike with a ratio of minimally 5 copies per cell. Lane 1, the S. aureus amplicon (MS2 RNA) at 100 copies/cell in RNA (3-h culture); lanes 2 to 6, DP 3 (MS2 RNA spike in RNA [3-h culture]) at 1 copy of MS2/cell and 5, 10, 50, and 100 copies of MS2/cell, respectively; lane 7, the MS 2 amplicon; lanes M, molecular size markers.