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Title: Regulation of carbapenem antibiotic production in Erwinia carotovora subspecies carotovora
Author: Barnard, A. M. L.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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Erwinia carotovora subspecies carotovora (Ecc) is a Gram-negative phytopathogen which causes the soft rot of various plant crops, including potato. Ecc strain GS101 produces the β-lactam antibiotic 1-carbapen-2-em-3-carboxylic acid (Car) during the transition from late log to stationary phase of growth. The major aim of this project was to identify novel regulators of Car production in Ecc, using random minitransposon (mini-Tn5) mutagenesis. Most of the Car mutants obtained had mini-Tn5 insertions in known Car regulators: carR, car1, or hor, or in Car biosynthetic genes. Some of the remaining mutants, potentially affected in novel regulatory loci, were studied further. Strain AB12 had a mini-Tn5 insertion in an open reading frame (orf), designated carK, which encoded an approximately 30 kDa protein. CarK showed sequence similarity to members of the LuxR family of transcriptional regulators. Transcription of the first gene in the Car biosynthetic cluster, carA, was increased in a carK mutant. Therefore, CarK might act as a repressor of carA transcription. The Car reduced strains AB1 and AB2 produced wild-type levels of N-(3-oxohexanoyl)-L-homoserine lactone, or OHHL. However, addition of exogenous OHHL restored Car production in these strains. carA and hor transcription were both affected in the AB1 genetic backgrounds. These mutants showed reduced exoenzyme production and reduced virulence, and therefore have a global effect on gene regulation in Ecc. A car strain, AB3, had a mini-Tn5 insertion of an orf designated carL. This mutation did not affect transcription of carA. CarL showed sequence similarity to periplasmic glutamine and glutamate/aspartate binding proteins. Two potentially translationally coupled genes encoding proteins with sequence similarity to glutamine and glutamate/aspartate ABC transporters were also identified downstream of carL.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available