Cloning and identification of the lytB locus in Escherichia coli

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dc.contributor.authorGustafson, Corinne Elaineen_US
dc.date.accessioned2024-08-13T22:57:55Z
dc.date.available2024-08-13T22:57:55Z
dc.date.copyright1991en_US
dc.date.issued1991
dc.degree.departmentDepartment of Biochemistry and Microbiology
dc.degree.levelMaster of Science M.Sc.en
dc.description.abstractThe phenotype conferred by a mutation in the lytB gene of Escherichia coli included temperature sensitive growth, and tolerance to penicillin-induced lysis at the restrictive temperature. These properties are correlated with the chronic accumulation of guanosine 5', 3'­-bispyrophosphate (ppGpp), the alarmone associated with induction of the stringent response, at the restrictive temperature. Suppression of ppGpp accumulation and the penicillin tolerance of this mutant at 42°C was accomplished by treatment with the ribosome inhibitor chloramphenicol, or by a relA- genetic background, suggesting that the stringent response is induced at the restrictive temperature. Based on these phenotypic properties, it is proposed that LytB may normally be responsible for maintaining RelA (ppGpp synthetase I) in its inactive state in growing bacteria, and the thermoinactivation of the temperature-sensitive mutant LytB protein results in the activation of the RelA enzyme at the restrictive temperature. The objective of this study was to identify the lytB gene. The lytB gene was cloned and identified by both deletion mapping and insertion mutagenesis. It was found to be the last open reading frame, designated orf316, in the ileS-lsp operon. Instability, in the form of spontaneous deletions and possibly point mutations, of plasmids carrying the lytB gene in high copy number indicated toxicity of the LytB protein when overexpressed. In support of this, it was shown that multicopy plasmids carrying an insertion-inactivated lytB gene were stable in multicopy. The possible basis for LytB toxicity is discussed.
dc.format.extent122 pages
dc.identifier.urihttps://hdl.handle.net/1828/17998
dc.rightsAvailable to the World Wide Weben_US
dc.titleCloning and identification of the lytB locus in Escherichia colien_US
dc.typeThesisen_US

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