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Co-ordinate regulation of antibiotic and pigment production by the Serratia Rap protein : evidence for a novel family of regulatory proteins
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Thomson, Nicholas Robert (1996) Co-ordinate regulation of antibiotic and pigment production by the Serratia Rap protein : evidence for a novel family of regulatory proteins. PhD thesis, University of Warwick.
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Official URL: http://webcat.warwick.ac.uk/record=b1402580~S15
Abstract
The enteric bacterium Serratia marcescens is an opportunistic human pathogen.
The strain studied here makes the red pigment prodigiosin (Pig) and the ß-lactam
antibiotic (5R)-carbapen-2-em-3 carboxylic acid. Mutants were isolated which were
affected for pigment production. Approximately 20% of these mutants were also
concomitantly deficient for the production of antibiotic. These mutants were presumed
to be defective in the rap (regulation of antibiotic and pigment) gene. This study set out
to investigate the rap gene which had been cloned by direct cosmid complementation of
a Rap mutant from a cosmid library (pNRT300). Sequence analysis of the rap gene
revealed a predicted product showing strong homology to S1yA, classified by Libby et
al., (1994) as a virulence determinant in Salmonella. Homologues of the rap gene were
detected in several genera including Salmonella, Yersinia, Enterobacter and species of
the enteric plant pathogen Erwinia. The Erwinia horEc gene (homologue of rap) was
cloned and encoded a product which was highly homologous to both the SlyA and Rap
proteins. The gene arrangement around the rap locus in Erwinia was identical to that in
Serratia in that rap and horEc were both situated upstream of two genes encoding
homologues of the lipoprotein Pcp and a gene encoding a protein of unknown function
from Yersinia enterocolitica. This observation led to the search for the Yersinia
homologue of rap (horte) which was subsequently cloned and sequenced. This gene too
encoded a protein highly homologous to Rap and HorE. Data base searches revealed
that these proteins shared a significant level of homology with a number of bacterial
protein regulators involved in exoenzyme production, virulence in plant and human
pathogens, multiple antibiotic resistance and xenobiotic catabolism. The findings of this
study cast serious doubt on the conclusions of Libby et al., (1994) and in a recent report
which was published whilst this thesis was being compiled, Ludwig et al., (1995)
reclassified S1yA as a regulatory protein capable of activating cryptic haemolysin genes
in Escherichia coll.
Marker exchange mutants (horEc:k: anR) of the Envinia carotovora subspecies
carotovora were found to be affected in the production of a carbapenem antibiotic and
showed decreased levels of production of multiple exoenzyme virulence factors.
Transcriptional fusion data revealed that the horEc mutation affected the transcription of
carA a carbapenem biosynthetic gene. Antibiotic and exoenzymes are known to be
regulated by a small molecule dependent regulatory system analogous to the Lux system
controlling bioluminescence in Photobacterium fischeri. The results of regulatory
studies in which autoinducer was added exogenously, or carR was added in trans imply
a role for HorE in this pheromone-signalling system.
The functional expression of prodigiosin in a Erwinia carotovora subspecies
carotovora was found to be dependent on autoinducer and the gene product of horEc.
Some interesting observations were also made regarding differential patterns of
prodigiosin gene expression within bacterial colonies. These patterning effects were
strikingly strain-specific.
Item Type: | Thesis (PhD) | ||||
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Subjects: | Q Science > QR Microbiology | ||||
Library of Congress Subject Headings (LCSH): | Serratia marcescens -- Genetics, Carboxylic acids -- Synthesis, Bacterial pigments -- Synthesis, Erwinia carotovora -- Genetics | ||||
Official Date: | May 1996 | ||||
Dates: |
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Institution: | University of Warwick | ||||
Theses Department: | Department of Biological Sciences | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Salmond, George | ||||
Sponsors: | Biotechnology and Biological Sciences Research Council (Great Britain) (BBSRC) | ||||
Extent: | xii, 172 p. | ||||
Language: | eng |
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