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Title: The role of murein hydrolases in the cell division of Escherichia coli
Author: Edwards, David Hugh
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1993
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Escherichia coli is a Gram-negative rod shaped bacterium that grows by lateral elongation before forming a septum at its centre and dividing into two daughter cells. During growth and division the cell's shape and integrity are maintained by a rigid cell wall or murein sacculus. This sacculus is essentially, a monolayer constructed from repeated peptidoglycan sub-units. The synthesis and hydrolysis of the cell wall is mediated by a number of enzymes, including a class of penicillin-sensitive proteins, the PBPs. One of these, PBP3, is a septum specific peptidoglycan synthetase. The work in this thesis is concerned with suppression to a temperature sensitive mutation (ftsI23) in the gene for PBP3. It is shown that FtsI23 can be suppressed by increased levels of the cell's major DD-carboxypeptidases, PBP5 and PBP6. A second known suppressor of ftsI mutations, sufI, is also shown to suppress ftsI23 by increasing the levels of PBP6 and membrane bound DD-carboxypeptidase activity. These results are proposed to indicate that PBP3 has a preference for 'tripeptide acceptors' as substrate. In conjunction with murein analysis of ftsI23 suppressed strains, it is further proposed that these acceptors are necessary for the formation of a set of critical but temporary 'tetrapeptide-tripeptide' cross-bridges. These cross-bridges are envisaged to be required for the incorporation of nascent peptidoglycan at the septum. To investigate this further a strain lacking all known periplasmic DD-carboxypeptidases was constructed. In addition the approximate locations of the gene for the LD-carboxypeptidase and dacC were mapped to 37 minutes and 19 minutes, respectively. It is also shown that strains completely lacking another peptidoglycan synthetase, RodA, grow as stable, mecillinam resistant spheres.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available