FIG 7.

Mechanism of HU action in B. subtilis cells. (A) HU inhibits RNR, preventing the conversion of rNDPs into dNDPs. (B) As a result, DNA replication is stalled, while purine and pyrimidine biosynthetic genes are upregulated to compensate for the lack of dNTPs (C). (D) B. subtilis cells upregulate efflux pumps and detoxification enzymes when challenged with HU. (E) RecA (green circles) binds ssDNA and eventually elicits the SOS response (F) when the threshold of ssDNA is reached. Red ovals represent catalase and peroxidases; yellow and orange membrane-bound proteins represent efflux pumps.