A. Farewell et al., ROLE OF THE ESCHERICHIA-COLI FADR REGULATOR IN STASIS SURVIVAL AND GROWTH PHASE-DEPENDENT EXPRESSION OF THE USPA, FAD, AND FAB GENES, Journal of bacteriology, 178(22), 1996, pp. 6443-6450
The increased expression of the uspA gene of Escherichia coli is an es
sential part of the cell's response to growth arrest, We demonstrate t
hat stationary-phase activation of the uspA promoter is in part depend
ent on growth phase-dependent inactivation or repression of the FadR r
egulator, Transcription of uspA is derepressed during exponential grow
th in fadR null mutants or by including the fatty acid oleate in the g
rowth medium of FadR(+) cells, The results of DNA footprinting analysi
s show that FadR binds downstream of the uspA promoter in the noncodin
g region, Thus, uspA is a member of the fadR regulon, All the fad-lacZ
fusions examined (fadBA, fadL, and fadD) are increasingly expressed i
n stationary phase with kinetics similar to that of the increased expr
ession of uspA. In contrast, beta-galactosidase levels decrease during
stationary phase in a fabA-lacZ lysogen, consistent with the role of
FadR as an activator of fabA. The growth phase-dependent increased and
decreased transcription of fad genes and fabA, respectively, is depen
dent on the status of the fadR gene, Cells carrying a mutation in the
FadR gene (fadRS219N) that makes it nonderepressible exhibit a weak st
ationary-phase induction of uspA and fad genes, In addition, cells car
rying fadRS219N sun ive long-term stasis poorly, indicating that FadR-
dependent alterations in fatty acid metabolism are an integral and imp
ortant part of the adaptation to stationary phase.