Figure 4.

Compound screening results using the negative and positive assays. (a). Negative assay in which SARS-CoV-2 3a protein is expressed at an elevated level (induction with 100 $\mathsf{\mu }$M $\mathsf{\beta }$-d-1-thiogalactopyranoside) and is therefore deleterious to DH10B bacteria. In this instance, inhibitory drugs enhance bacterial growth. (b). Positive assay in which SARS-CoV-2 3a protein is expressed at a low level (12.5 $\mathsf{\mu }$M $\mathsf{\beta }$-d-1-thiogalactopyranoside) in K⁺-uptake deficient bacteria (LB650). In this instance, inhibitory drugs reduce bacterial growth. The results in both panels may be compared to those obtained without any drug (gray) or when the channel is uninduced (black). The color scale indicates the different concentrations of the chemicals, which were performed in duplicates.