Figure 3.

NO inhibits transcription of SPI2 effectors encoded in multiple loci of the Salmonella chromosome. (A) The effect of NO on transcription of several SPI2 lacZ transcriptional fusions was analyzed by measuring β-galactosidase as described in Fig. 2. These data represent the means ± SEM of two to five independent observations from two separate experiments. Transcription of the sifA and sseG SPI2 effectors (B) and the ssrA sensor kinase (C) was assessed by RT-PCR of RNA samples isolated from WT Salmonella grown in SPI2-inducing conditions in the presence or absence of the NO generator spermine NONOate as outlined in Fig. 2. (D) RT-PCR of hmp and rpoD transcripts isolated from Salmonella cultures grown in 8 μM MgCl₂ N salts medium in the presence or absence of 750 μM spermine NONOate. (E) The effects of the NO on hmp transcription were independently studied by measuring the activity of the hmp::lacZ transcriptional fusion expressed by Salmonella strain AV0305. The bacteria were grown in 8 μM MgCl₂ N salts medium in the presence or absence of 750 μM spermine NONOate. These data represent the means ± SD of three independent observations.