Simon Park | University of Surrey (original) (raw)

Papers by Simon Park

Research paper thumbnail of Growth of Campylobacter jejuni on nitrate and nitrite: electron transport to NapA and NrfA via NrfH and distinct roles for NrfA and the globin Cgb in protection against nitrosative stress: Roles of Nap and Nrf systems in C. jejuni

Molecular Microbiology, 2006

Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have b... more Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have been investigated in Campylobacter jejuni, a microaerophilic food-borne pathogen. The nap operon is unusual in lacking napC (encoding a tetra-haem c-type cytochrome) and napF, but contains a novel gene of unknown function, napL. The iron-sulphur protein NapG has a major role in electron transfer to the NapAB complex, but we show that slow nitrate-dependent growth of a napG mutant can be sustained by electron transfer from NrfH, the electron donor to the nitrite reductase NrfA. A napL mutant possessed ∼50% lower NapA activity than the wild type but showed normal growth with nitrate as the electron acceptor. NrfA was constitutive and was shown to play a role in protection against nitrosative stress in addition to the previously identified NO-inducible single domain globin, Cgb. However, nitrite also induced cgb expression in an NssR-dependent manner, suggesting that growth of C. jejuni with nitrite causes nitrosative stress. This was confirmed by lack of growth of cgb and nssR mutants, and slow growth of the nrfA mutant, in media containing nitrite. Thus, NrfA and Cgb together provide C. jejuni with constitutive and inducible components of a robust defence against nitrosative stress.

Research paper thumbnail of NssR, a member of the Crp-Fnr superfamily from Campylobacter jejuni, regulates a nitrosative stress-responsive regulon that includes both a single-domain and a truncated haemoglobin

Molecular Microbiology, 2005

Consistent with its role as a nitric oxide (NO)-detoxifying globin in Campylobacter jejuni, Cgb (... more Consistent with its role as a nitric oxide (NO)-detoxifying globin in Campylobacter jejuni, Cgb (Campylobacter globin) expression is strongly and specifically induced following exposure to nitrosative stress, suggesting a previously unrecognized capacity for NO-related stress sensing in this food-borne pathogen. In this study, Fur and PerR have been eliminated as major regulators of cgb, and NssR (Cj0466), a member of the Crp-Fnr superfamily, has been identified as the major positive regulatory factor that controls nitrosative stress-responsive expression of this gene. Accordingly, disruption of nssR resulted in the abolition of inducible cgb expression, which was restored by a complementing chromosomal insertion of the wild-type gene with its indigenous promoter at a second location. The NssR-deficient mutant was more sensitive to NO-related stress than a cgb mutant and this phenotype most likely arises from the failure of these cells to induce other NO-responsive components in addition to Cgb. Indeed, analysis of global gene expression, by microarray and confirmatory real-time polymerase chain reaction (PCR) in the wild type and nssR mutant, not only confirmed the dependence of inducible cgb expression on NssR, but also revealed for the first time a novel NssR-dependent nitrosative stress-responsive regulon. This regulon of at least four genes includes Cj0465c, a truncated globin. Consistent with NssR being a Crp-Fnr superfamily member, an Fnr-like binding sequence (TTAAC-N4-GTTAA) was found upstream of each gene at locations −40.5 to −42.5 relative to the centre of the binding sites and the transcription start point. Site-directed mutagenesis confirmed that this cis-acting motif mediates the nitrosative stress-inducible expression of cgb.

Research paper thumbnail of High-efficiency transformation of Listeria monocytogenes by electroporation of penicillin-treated cells

Research paper thumbnail of Specific Identification of the Enteropathogens Campylobacter Jejuni and Campylobacter Coli by Using a PCR Test Based on the CeuE Gene Encoding a Putative …

Journal of clinical …, Jan 1, 1997

Research paper thumbnail of The physiology of Campylobacter species and its relevance to their role as foodborne pathogens

International journal of food microbiology, Jan 1, 2002

Research paper thumbnail of Expression of Listeriolysin and Phosphatidylinositol-Specific Phospholipase C is Repressed by the Plant-Derived Molecule Cellobiose In Listeria Monocytogenes

Molecular microbiology, Jan 1, 1993

The primary habitat of the intracellular pathogen Listeria monocytogenes is considered to be soil... more The primary habitat of the intracellular pathogen Listeria monocytogenes is considered to be soil and decaying vegetation. As an opportunistic pathogen it must be able to recognize its entry into host tissue and, in response, co-ordinately induce the expression of virulence factors. No signature molecule, which facilitates this regulation, has been identified for any human pathogen. Our studies have demonstrated for the first time that the expression of major virulence determinants in L. monocytogenes can be repressed by an environmentally ubiquitous molecule. Transcriptional hlyA and plcA fusions to luxAB were used to monitor virulent gene expression in the presence of various disaccharides. These studies revealed that the expression of listeriolysin O and phosphatidylinositol-specific phospholipase C is repressed specifically by the plant-derived disaccharide, cellobiose.

Research paper thumbnail of Quorum Sensing In Campylobacter Jejuni: Detection of a LuxS Encoded Signalling Molecule

Microbiology, Jan 1, 2002

Research paper thumbnail of The role of iron in Campylobacter gene regulation, metabolism and oxidative stress defense

FEMS microbiology …, Jan 1, 2002

Research paper thumbnail of Enterochelin Acquisition In Campylobacter Coli: Characterization of Components of a Binding-Protein-Dependent Transport System

Microbiology, Jan 1, 1995

Research paper thumbnail of Generation of a Superoxide Dismutase (SOD)-Deficient Mutant of Campylobacter Coli: Evidence for the Significance of SOD In Campylobacter Survival and Colonization

Applied and …, Jan 1, 1999

Research paper thumbnail of Molecular Characterization of PldA, the Structural Gene for a Phospholipase A From Campylobacter Coli, and Its Contribution to Cell-Associated Hemolysis

Infection and …, Jan 1, 1997

Research paper thumbnail of Augmentation of Killing of Escherichia Coli O157 by Combinations of Lactate, Ethanol, and Low-PH Conditions

Applied and …, Jan 1, 1999

Research paper thumbnail of Molecular Genetics of Bacteria

Page 1. JEREMY W. DALE SIMON F. PARK 6> Molecular Genetics of Bacteria WILEY-BLACKWELL Pag... more Page 1. JEREMY W. DALE SIMON F. PARK 6> Molecular Genetics of Bacteria WILEY-BLACKWELL Page 2. Molecular Genetics of Bacteria 5th edition Page 3. Page 4. Molecular Genetics of Bacteria 5th edition Jeremy W. Dale ...

Research paper thumbnail of Role of An Inducible Single-Domain Hemoglobin In Mediating Resistance to Nitric Oxide and Nitrosative Stress In Campylobacter Jejuni and Campylobacter Coli

Journal of …, Jan 1, 2004

Research paper thumbnail of Osmotic and growth-phase dependent regulation of the eta gene of Staphylococcus aureus: a role for DNA supercoiling

Molecular and General …, Jan 1, 1992

Research paper thumbnail of Variation In Resistance to High Hydrostatic Pressure and RpoS Heterogeneity In Natural Isolates of Escherichia Coli O157: H7

Applied and …, Jan 1, 2001

Research paper thumbnail of Molecular Characterization of KatA From Campylobacter Jejuni and Generation of a Catalase-Deficient Mutant of Campylobacter Coli by Interspecific Allelic Exchange

Microbiology, Jan 1, 1995

Research paper thumbnail of Molecular Characterization of a Campylobacter Jejuni Lipoprotein With Homology to Periplasmic Siderophore-Binding Proteins

Journal of bacteriology, Jan 1, 1995

Research paper thumbnail of Differential Uptake and Killing Potential of Campylobacter Jejuni by Human Peripheral Monocytes/Macrophages

Medical microbiology …, Jan 1, 1997

Research paper thumbnail of Survival of Campylobacter Jejuni During Stationary Phase: Evidence for the Absence of a Phenotypic Stationary-Phase Response

Applied and …, Jan 1, 2001

When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39°C, entry int... more When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39°C, entry into stationary phase was followed by a rapid decline in viable numbers to leave a residual population of 1% of the maximum number or less. Loss of viability was preceded by sublethal injury, which was seen as a loss of the ability to grow on media containing 0.1% sodium deoxycholate or 1% sodium chloride. Resistance of cells to mild heat stress (50°C) or aeration was greatest in exponential phase and declined during early stationary phase. These results show that C. jejuni does not mount the normal phenotypic stationary-phase response which results in enhanced stress resistance. This conclusion is consistent with the absence of rpoS homologues in the recently reported genome sequence of this species and their probable absence from strain NCTC 11351. During prolonged incubation of C. jejuni NCTC 11351 in stationary phase, an unusual pattern of decreasing and increasing heat resistance was observed that coincided with fluctuations in the viable count. During stationary phase of Campylobacter coli UA585, nonmotile variants and those with impaired ability to form coccoid cells were isolated at high frequency. Taken together, these observations suggest that stationary-phase cultures of campylobacters are dynamic populations and that this may be a strategy to promote survival in at least some strains. Investigation of two spontaneously arising variants (NM3 and SC4) of C. coli UA585 showed that a reduced ability to form coccoid cells did not affect survival under nongrowth conditions.

Research paper thumbnail of Growth of Campylobacter jejuni on nitrate and nitrite: electron transport to NapA and NrfA via NrfH and distinct roles for NrfA and the globin Cgb in protection against nitrosative stress: Roles of Nap and Nrf systems in C. jejuni

Molecular Microbiology, 2006

Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have b... more Pathways of electron transport to periplasmic nitrate (NapA) and nitrite (NrfA) reductases have been investigated in Campylobacter jejuni, a microaerophilic food-borne pathogen. The nap operon is unusual in lacking napC (encoding a tetra-haem c-type cytochrome) and napF, but contains a novel gene of unknown function, napL. The iron-sulphur protein NapG has a major role in electron transfer to the NapAB complex, but we show that slow nitrate-dependent growth of a napG mutant can be sustained by electron transfer from NrfH, the electron donor to the nitrite reductase NrfA. A napL mutant possessed ∼50% lower NapA activity than the wild type but showed normal growth with nitrate as the electron acceptor. NrfA was constitutive and was shown to play a role in protection against nitrosative stress in addition to the previously identified NO-inducible single domain globin, Cgb. However, nitrite also induced cgb expression in an NssR-dependent manner, suggesting that growth of C. jejuni with nitrite causes nitrosative stress. This was confirmed by lack of growth of cgb and nssR mutants, and slow growth of the nrfA mutant, in media containing nitrite. Thus, NrfA and Cgb together provide C. jejuni with constitutive and inducible components of a robust defence against nitrosative stress.

Research paper thumbnail of NssR, a member of the Crp-Fnr superfamily from Campylobacter jejuni, regulates a nitrosative stress-responsive regulon that includes both a single-domain and a truncated haemoglobin

Molecular Microbiology, 2005

Consistent with its role as a nitric oxide (NO)-detoxifying globin in Campylobacter jejuni, Cgb (... more Consistent with its role as a nitric oxide (NO)-detoxifying globin in Campylobacter jejuni, Cgb (Campylobacter globin) expression is strongly and specifically induced following exposure to nitrosative stress, suggesting a previously unrecognized capacity for NO-related stress sensing in this food-borne pathogen. In this study, Fur and PerR have been eliminated as major regulators of cgb, and NssR (Cj0466), a member of the Crp-Fnr superfamily, has been identified as the major positive regulatory factor that controls nitrosative stress-responsive expression of this gene. Accordingly, disruption of nssR resulted in the abolition of inducible cgb expression, which was restored by a complementing chromosomal insertion of the wild-type gene with its indigenous promoter at a second location. The NssR-deficient mutant was more sensitive to NO-related stress than a cgb mutant and this phenotype most likely arises from the failure of these cells to induce other NO-responsive components in addition to Cgb. Indeed, analysis of global gene expression, by microarray and confirmatory real-time polymerase chain reaction (PCR) in the wild type and nssR mutant, not only confirmed the dependence of inducible cgb expression on NssR, but also revealed for the first time a novel NssR-dependent nitrosative stress-responsive regulon. This regulon of at least four genes includes Cj0465c, a truncated globin. Consistent with NssR being a Crp-Fnr superfamily member, an Fnr-like binding sequence (TTAAC-N4-GTTAA) was found upstream of each gene at locations −40.5 to −42.5 relative to the centre of the binding sites and the transcription start point. Site-directed mutagenesis confirmed that this cis-acting motif mediates the nitrosative stress-inducible expression of cgb.

Research paper thumbnail of High-efficiency transformation of Listeria monocytogenes by electroporation of penicillin-treated cells

Research paper thumbnail of Specific Identification of the Enteropathogens Campylobacter Jejuni and Campylobacter Coli by Using a PCR Test Based on the CeuE Gene Encoding a Putative …

Journal of clinical …, Jan 1, 1997

Research paper thumbnail of The physiology of Campylobacter species and its relevance to their role as foodborne pathogens

International journal of food microbiology, Jan 1, 2002

Research paper thumbnail of Expression of Listeriolysin and Phosphatidylinositol-Specific Phospholipase C is Repressed by the Plant-Derived Molecule Cellobiose In Listeria Monocytogenes

Molecular microbiology, Jan 1, 1993

The primary habitat of the intracellular pathogen Listeria monocytogenes is considered to be soil... more The primary habitat of the intracellular pathogen Listeria monocytogenes is considered to be soil and decaying vegetation. As an opportunistic pathogen it must be able to recognize its entry into host tissue and, in response, co-ordinately induce the expression of virulence factors. No signature molecule, which facilitates this regulation, has been identified for any human pathogen. Our studies have demonstrated for the first time that the expression of major virulence determinants in L. monocytogenes can be repressed by an environmentally ubiquitous molecule. Transcriptional hlyA and plcA fusions to luxAB were used to monitor virulent gene expression in the presence of various disaccharides. These studies revealed that the expression of listeriolysin O and phosphatidylinositol-specific phospholipase C is repressed specifically by the plant-derived disaccharide, cellobiose.

Research paper thumbnail of Quorum Sensing In Campylobacter Jejuni: Detection of a LuxS Encoded Signalling Molecule

Microbiology, Jan 1, 2002

Research paper thumbnail of The role of iron in Campylobacter gene regulation, metabolism and oxidative stress defense

FEMS microbiology …, Jan 1, 2002

Research paper thumbnail of Enterochelin Acquisition In Campylobacter Coli: Characterization of Components of a Binding-Protein-Dependent Transport System

Microbiology, Jan 1, 1995

Research paper thumbnail of Generation of a Superoxide Dismutase (SOD)-Deficient Mutant of Campylobacter Coli: Evidence for the Significance of SOD In Campylobacter Survival and Colonization

Applied and …, Jan 1, 1999

Research paper thumbnail of Molecular Characterization of PldA, the Structural Gene for a Phospholipase A From Campylobacter Coli, and Its Contribution to Cell-Associated Hemolysis

Infection and …, Jan 1, 1997

Research paper thumbnail of Augmentation of Killing of Escherichia Coli O157 by Combinations of Lactate, Ethanol, and Low-PH Conditions

Applied and …, Jan 1, 1999

Research paper thumbnail of Molecular Genetics of Bacteria

Page 1. JEREMY W. DALE SIMON F. PARK 6> Molecular Genetics of Bacteria WILEY-BLACKWELL Pag... more Page 1. JEREMY W. DALE SIMON F. PARK 6> Molecular Genetics of Bacteria WILEY-BLACKWELL Page 2. Molecular Genetics of Bacteria 5th edition Page 3. Page 4. Molecular Genetics of Bacteria 5th edition Jeremy W. Dale ...

Research paper thumbnail of Role of An Inducible Single-Domain Hemoglobin In Mediating Resistance to Nitric Oxide and Nitrosative Stress In Campylobacter Jejuni and Campylobacter Coli

Journal of …, Jan 1, 2004

Research paper thumbnail of Osmotic and growth-phase dependent regulation of the eta gene of Staphylococcus aureus: a role for DNA supercoiling

Molecular and General …, Jan 1, 1992

Research paper thumbnail of Variation In Resistance to High Hydrostatic Pressure and RpoS Heterogeneity In Natural Isolates of Escherichia Coli O157: H7

Applied and …, Jan 1, 2001

Research paper thumbnail of Molecular Characterization of KatA From Campylobacter Jejuni and Generation of a Catalase-Deficient Mutant of Campylobacter Coli by Interspecific Allelic Exchange

Microbiology, Jan 1, 1995

Research paper thumbnail of Molecular Characterization of a Campylobacter Jejuni Lipoprotein With Homology to Periplasmic Siderophore-Binding Proteins

Journal of bacteriology, Jan 1, 1995

Research paper thumbnail of Differential Uptake and Killing Potential of Campylobacter Jejuni by Human Peripheral Monocytes/Macrophages

Medical microbiology …, Jan 1, 1997

Research paper thumbnail of Survival of Campylobacter Jejuni During Stationary Phase: Evidence for the Absence of a Phenotypic Stationary-Phase Response

Applied and …, Jan 1, 2001

When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39°C, entry int... more When Campylobacter jejuni NCTC 11351 was grown microaerobically in rich medium at 39°C, entry into stationary phase was followed by a rapid decline in viable numbers to leave a residual population of 1% of the maximum number or less. Loss of viability was preceded by sublethal injury, which was seen as a loss of the ability to grow on media containing 0.1% sodium deoxycholate or 1% sodium chloride. Resistance of cells to mild heat stress (50°C) or aeration was greatest in exponential phase and declined during early stationary phase. These results show that C. jejuni does not mount the normal phenotypic stationary-phase response which results in enhanced stress resistance. This conclusion is consistent with the absence of rpoS homologues in the recently reported genome sequence of this species and their probable absence from strain NCTC 11351. During prolonged incubation of C. jejuni NCTC 11351 in stationary phase, an unusual pattern of decreasing and increasing heat resistance was observed that coincided with fluctuations in the viable count. During stationary phase of Campylobacter coli UA585, nonmotile variants and those with impaired ability to form coccoid cells were isolated at high frequency. Taken together, these observations suggest that stationary-phase cultures of campylobacters are dynamic populations and that this may be a strategy to promote survival in at least some strains. Investigation of two spontaneously arising variants (NM3 and SC4) of C. coli UA585 showed that a reduced ability to form coccoid cells did not affect survival under nongrowth conditions.