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Title: Control of the sequential utilisation of some sugars by Escherichia coli ATCC 15224
Author: Clark, Barry
ISNI:       0000 0001 3552 7206
Awarding Body: University of Glasgow
Current Institution: University of Glasgow
Date of Award: 1974
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1. The glucose and fructose phosphotransferase systems (PTS) of E. coli 15224 are constitutive but increase about 7-fold in the presence of their substrates. However, inoculation of glucose trained cells into fructose medium leads to a rapid increase in fructose PTS activity which overshoots the final value obtained. This overshoot is prevented by chloramphenicol suggesting that it results from de novo synthesis rather than activation of a precursor. The magnitude of the overshoot is directly linked to the degree of catabolite repression existing before transfer into fructose alone and the overshoot does not occur in the presence of exogenous cyclic MIP. 2. Glucose challenge to fructose growing cells eventually results in sequential utilisation of the glucose and fructose since glucose both represses the synthesis of, and inhibits the activity of, the fructose PTS, Near glucose exhaustion fructose PTS synthesis is rapidly induced and the activity overshoots the final value. This allows a short period of co-utilisation explaining the absence of diauxie for E.coli 15224 growing on glucose and fructose. 3. Rates of sugar utilisation in vivo are not directly related to the PTS activities measured in vitro suggesting that, in vivo, the PTS's are under inhibitory control. 4. Glucose inhibition of fructose utilisation requires induction of the glucose PTS, The use of protein-reacting reagents shows that the interaction of glucose with the glucose PTS prevents fructose binding to the fructose PTS and thus inhibits fructose utilisation. Hexose-phosphates may also be implicated in this inhibition of fructose utilisation but the data suggest that they are more likely to be involved in the normal mechanism of controlling carbon flux into the cell. 5. The sequential utilisation of glucose and fructose is thus mediated, by control of their respective PTS activities.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available