We next tested whether the 6S RNA-dependent change in
ppGpp levels might be sufficient to lead to altered
transcription of promoters sensitive to ppGpp. For these
experiments we chose to examine promoter–lacZ reporters
previously described in studies examining ppGpp and 6S
RNA-dependent regulation (Barker et al., 2001; Trotochaud
& Wassarman, 2004; Cavanagh et al., 2008). Note that
although many of the genes examined also are regulated by
attenuation or other mechanisms after transcription initiation,
the reporters used here contain only minimal
promoter sequences lacking elements mediating attenuation,
and therefore should be representative of regulation at
transcription initiation.