TY - JOUR
T1 - The multifactorial influences of RpoS, Mlc and cAMP on ptsG expression under glucose-limited and anaerobic conditions
AU - Seeto, Shona
AU - Notley-McRobb, Lucinda
AU - Ferenci, Thomas
PY - 2004/4
Y1 - 2004/4
N2 - The ptsG gene encodes the high-affinity glucose receptor component of the PEP:glucose phosphotransferase system. PtsG is the major glucose transporter in Escherichia coli under glucose-excess conditions but its regulation under glucose limitation or anaerobiosis is poorly defined. Using a ptsG-lacZ transcriptional fusion, ptsG expression was found to peak with low (micromolar) external glucose levels in glucose-limited chemostats, so PtsG is primed to contribute to glucose scavenging under hunger response conditions. This regulatory pattern was confirmed using methyl-α-glucoside transport assays of PtsG-dependent transport. The regulation of ptsG by cAMP contributed to the optimal expression with micromolar glucose but ptsG was actually repressed to levels below that in glucose-excess batch cultures at very slow growth rates and submicromolar glucose concentrations. RpoS contributed to repression of ptsG in slow-growing bacteria but not under glucose-excess conditions. Also, Mlc increasingly contributed to the repression of ptsG at residual glucose concentrations too low to saturate PtsG. A similar pattern of ptsG regulation was observed in anaerobic cultures with either glucose-excess or glucose-limiting situations.
AB - The ptsG gene encodes the high-affinity glucose receptor component of the PEP:glucose phosphotransferase system. PtsG is the major glucose transporter in Escherichia coli under glucose-excess conditions but its regulation under glucose limitation or anaerobiosis is poorly defined. Using a ptsG-lacZ transcriptional fusion, ptsG expression was found to peak with low (micromolar) external glucose levels in glucose-limited chemostats, so PtsG is primed to contribute to glucose scavenging under hunger response conditions. This regulatory pattern was confirmed using methyl-α-glucoside transport assays of PtsG-dependent transport. The regulation of ptsG by cAMP contributed to the optimal expression with micromolar glucose but ptsG was actually repressed to levels below that in glucose-excess batch cultures at very slow growth rates and submicromolar glucose concentrations. RpoS contributed to repression of ptsG in slow-growing bacteria but not under glucose-excess conditions. Also, Mlc increasingly contributed to the repression of ptsG at residual glucose concentrations too low to saturate PtsG. A similar pattern of ptsG regulation was observed in anaerobic cultures with either glucose-excess or glucose-limiting situations.
KW - cAMP
KW - Chemostat populations
KW - Glucose limitation
KW - Glucose transport
KW - mlc mutation
KW - rpoS
UR - http://www.scopus.com/inward/record.url?scp=1842471052&partnerID=8YFLogxK
U2 - 10.1016/j.resmic.2003.11.011
DO - 10.1016/j.resmic.2003.11.011
M3 - Article
C2 - 15059634
AN - SCOPUS:1842471052
VL - 155
SP - 211
EP - 215
JO - Research in Microbiology
JF - Research in Microbiology
SN - 0923-2508
IS - 3
ER -