scholarly journals OmpR and LeuO Positively Regulate the Salmonella enterica Serovar Typhi ompS2 Porin Gene

2004 ◽  
Vol 186 (10) ◽  
pp. 2909-2920 ◽  
Author(s):  
Marcos Fernández-Mora ◽  
José Luis Puente ◽  
Edmundo Calva
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Phosphorylation Site ◽  
Regulatory Region ◽  
Random Mutagenesis ◽  
Fold Increase ◽  
Upstream Regulatory Region ◽  
Wild Type ◽  
Transposon Insertion

ABSTRACT The Salmonella enterica serovar Typhi ompS2 gene codes for a 362-amino-acid outer membrane protein that contains motifs common to the porin superfamily. It is expressed at very low levels compared to the major OmpC and OmpF porins, as observed for S. enterica serovar Typhi OmpS1, Escherichia coli OmpN, and Klebsiella pneumoniae OmpK37 quiescent porins. A region of 316 bp, between nucleotides −413 and −97 upstream of the transcriptional start point, is involved in negative regulation, as its removal resulted in a 10-fold increase in ompS2 expression in an S. enterica serovar Typhi wild-type strain. This enhancement in expression was not observed in isogenic mutant strains, which had specific deletions of the regulatory ompB (ompR envZ) operon. Furthermore, ompS2 expression was substantially reduced in the presence of the OmpR D55A mutant, altered in the major phosphorylation site. Upon random mutagenesis, a mutant where the transposon had inserted into the upstream regulatory region of the gene coding for the LeuO regulator, showed an increased level of ompS2 expression. Augmented expression of ompS2 was also obtained upon addition of cloned leuO to the wild-type strain, but not in an ompR isogenic derivative, consistent with the notion that the transposon insertion had increased the cellular levels of LeuO and with the observed dependence on OmpR. Moreover, LeuO and OmpR bound in close proximity, but independently, to the 5′ upstream regulatory region. Thus, the OmpR and LeuO regulators positively regulate ompS2.

scholarly journals Salmonella enterica subspecies enterica serovar Enteritidis Salmonella pathogenicity island 2 type III secretion system: role in intestinal colonization of chickens and systemic spread

Microbiology ◽  
2010 ◽  
Vol 156 (9) ◽  
pp. 2770-2781 ◽  
Author(s):  
Amanda L. S. Wisner ◽  
Taseen S. Desin ◽  
Birgit Koch ◽  
Po-King S. Lam ◽  
Emil M. Berberov ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Host Cells ◽  
Wild Type ◽  
Type Iii ◽  
Systemic Spread

Salmonella enterica subspecies enterica serovar Enteritidis (S. Enteritidis) has been identified as a significant cause of salmonellosis in humans. Salmonella pathogenicity islands 1 and 2 (SPI-1 and SPI-2) each encode a specialized type III secretion system (T3SS) that enables Salmonella to manipulate host cells at various stages of the invasion/infection process. For the purposes of our studies we used a chicken isolate of S. Enteritidis (Sal18). In one study, we orally co-challenged 35-day-old specific pathogen-free (SPF) chickens with two bacterial strains per group. The control group received two versions of the wild-type strain Sal18: Sal18 attTn7 : : tet and Sal18 attTn7 : : cat, while the other two groups received the wild-type strain (Sal18 attTn7 : : tet) and one of two mutant strains. From this study, we concluded that S. Enteritidis strains deficient in the SPI-1 and SPI-2 systems were outcompeted by the wild-type strain. In a second study, groups of SPF chickens were challenged at 1 week of age with four different strains: the wild-type strain, and three other strains lacking either one or both of the SPI-1 and SPI-2 regions. On days 1 and 2 post-challenge, we observed a reduced systemic spread of the SPI-2 mutants, but by day 3, the systemic distribution levels of the mutants matched that of the wild-type strain. Based on these two studies, we conclude that the S. Enteritidis SPI-2 T3SS facilitates invasion and systemic spread in chickens, although alternative mechanisms for these processes appear to exist.

scholarly journals A Plasmid-Encoded FetMP-Fls Iron Uptake System Confers Selective Advantages to Salmonella enterica Serovar Typhimurium in Growth under Iron-Restricted Conditions and for Infection of Mammalian Host Cells

2020 ◽  
Vol 8 (5) ◽  
pp. 630
Author(s):  
Vanesa García ◽  
Ana Herrero-Fresno ◽  
Rosaura Rodicio ◽  
Alfonso Felipe-López ◽  
Ignacio Montero ◽  
...  
Keyword(s):  
Iron Content ◽  
Salmonella Enterica ◽  
Iron Uptake ◽  
Type Strain ◽  
Wild Type Strain ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Iron Acquisition ◽  
Clinical Strain ◽  
Wild Type ◽  
Serovar Typhimurium

The resistance plasmid pUO-StVR2, derived from virulence plasmid pSLT, is widespread in clinical isolates of Salmonella enterica serovar Typhimurium recovered in Spain and other European countries. pUO-StVR2 carries several genes encoding a FetMP-Fls system, which could be involved in iron uptake. We therefore analyzed S. Typhimurium LSP 146/02, a clinical strain selected as representative of the isolates carrying the plasmid, and an otherwise isogenic mutant lacking four genes (fetMP-flsDA) of the fetMP-fls region. Growth curves and determination of the intracellular iron content under iron-restricted conditions demonstrated that deletion of these genes impairs iron acquisition. Thus, under these conditions, the mutant grew significantly worse than the wild-type strain, its iron content was significantly lower, and it was outcompeted by the wild-type strain in competition assays. Importantly, the strain lacking the fetMP-flsDA genes was less invasive in cultured epithelial HeLa cells and replicated poorly upon infection of RAW264.7 macrophages. The genes were introduced into S. Typhimurium ATCC 14028, which lacks the FetMP-Fls system, and this resulted in increased growth under iron limitation as well as an increased ability to multiply inside macrophages. These findings indicate that the FetMP-Fls iron acquisition system exceeds the benefits conferred by the other high-affinity iron uptake systems carried by ATCC 14028 and LSP 146/02. We proposed that effective iron acquisition by this system in conjunction with antimicrobial resistance encoded from the same plasmid have greatly contributed to the epidemic success of S. Typhimurium isolates harboring pUO-StVR2.

scholarly journals Oral Immunization with an rfaH Mutant Elicits Protection against Salmonellosis in Mice

2004 ◽  
Vol 72 (7) ◽  
pp. 4297-4301 ◽  
Author(s):  
Gábor Nagy ◽  
Ulrich Dobrindt ◽  
Jörg Hacker ◽  
Levente Emödy
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Lethal Dose ◽  
Fold Increase ◽  
Oral Immunization ◽  
Oral Infection ◽  
Wild Type ◽  
Virulence Attenuation ◽  
Serovar Typhimurium

ABSTRACT Loss of the transcriptional antiterminator RfaH results in virulence attenuation (>104-fold increase in 50% lethal dose) of the archetypal Salmonella enterica serovar Typhimurium strain SL1344 by both orogastric and intraperitoneal routes of infection in BALB/c mice. Oral immunization with the mutant efficiently protects mice against a subsequent oral infection with the wild-type strain. Interestingly, in vitro immunoreactivity is not confined to strain SL1344; rather, it is directed also towards other serovars of S. enterica and even Salmonella bongori strains.

scholarly journals Temperature-Sensitive Salmonella enterica Serovar Enteritidis PT13a Expressing Essential Proteins of Psychrophilic Bacteria

2015 ◽  
Vol 81 (19) ◽  
pp. 6757-6766 ◽  
Author(s):  
Barry N. Duplantis ◽  
Stephanie M. Puckett ◽  
Everett L. Rosey ◽  
Keith A. Ameiss ◽  
Angela D. Hartman ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Phage Type ◽  
The Body ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Wild Type ◽  
Psychrophilic Bacteria ◽  
Content Type

ABSTRACTSynthetic genes based on deduced amino acid sequences of the NAD-dependent DNA ligase (ligA) and CTP synthetase (pyrG) of psychrophilic bacteria were substituted for their native homologues in the genome ofSalmonella entericaserovar Enteritidis phage type 13a (PT13a). The resulting strains were rendered temperature sensitive (TS) and did not revert to temperature resistance at a detectable level. At permissive temperatures, TS strains grew like the parental strain in broth medium and in macrophage-like cells, but their growth was slowed or stopped when they were shifted to a restrictive temperature. When injected into BALB/c mice at the base of the tail, representing a cool site of the body, the strains with restrictive temperatures of 37, 38.5, and 39°C persisted for less than 1 day, 4 to 7 days, and 20 to 28 days, respectively. The wild-type strain persisted at the site of inoculation for at least 28 days. The wild-type strain, but not the TS strains, was also found in spleen-plus-liver homogenates within 1 day of inoculation of the tail and was detectable in these organs for at least 28 days. Intramuscular vaccination of White Leghorn chickens with the PT13a strain carrying the psychrophilicpyrGgene provided some protection against colonization of the reproductive tract and induced an anti-S. entericaantibody response.

scholarly journals Osmoregulated periplasmic glucans of Salmonella enterica serovar Typhimurium are required for optimal virulence in mice

Microbiology ◽  
2009 ◽  
Vol 155 (1) ◽  
pp. 229-237 ◽  
Author(s):  
Arvind A. Bhagwat ◽  
Won Jun ◽  
Liu Liu ◽  
Porteen Kannan ◽  
Mahesh Dharne ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Gene Cassette ◽  
Growth Conditions ◽  
Kanamycin Resistance ◽  
Wild Type ◽  
Serovar Typhimurium ◽  
Resistance Gene Cassette ◽  
Reduced Rate

We purified osmoregulated periplasmic glucans (OPGs) from Salmonella enterica serovar Typhimurium and found them to be composed of 100 % glucose with 2-linked glucose as the most abundant residue, with terminal glucose, 2,3-linked and 2,6-linked glucose also present in high quantities. The two structural genes for OPG biosynthesis, opgG and opgH, form a bicistronic operon, and insertion of a kanamycin resistance gene cassette into this operon resulted in a strain devoid of OPGs. The opgGH mutant strain was impaired in motility and growth under low osmolarity conditions. The opgGH mutation also resulted in a 2 log increase in the LD50 in mice compared to the wild-type strain SL1344. Inability to synthesize OPGs had no significant impact on the organism's lipopolysaccharide pattern or its ability to survive antimicrobial peptides-, detergent-, pH- and nutrient-stress conditions. We observed that the opgGH-defective strain respired at a reduced rate under acidic growth conditions (pH 5.0) and had lower ATP levels compared to the wild-type strain. These data indicate that OPGs of S. Typhimurium contribute towards mouse virulence as well as growth and motility under low osmolarity growth conditions.

scholarly journals LuxS-Based Quorum Sensing Does Not Affect the Ability of Salmonella enterica Serovar Typhimurium To Express the SPI-1 Type 3 Secretion System, Induce Membrane Ruffles, or Invade Epithelial Cells

2009 ◽  
Vol 191 (23) ◽  
pp. 7253-7259 ◽  
Author(s):  
Charlotte A. Perrett ◽  
Michail H. Karavolos ◽  
Suzanne Humphrey ◽  
Pietro Mastroeni ◽  
Isabel Martinez-Argudo ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Quorum Sensing ◽  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Protein Fusion ◽  
Serovar Typhimurium ◽  
In The Wild ◽  
Type 3

ABSTRACT Bacterial species can communicate by producing and sensing small autoinducer molecules by a process known as quorum sensing. Salmonella enterica produces autoinducer 2 (AI-2) via the luxS synthase gene, which is used by some bacterial pathogens to coordinate virulence gene expression with population density. We investigated whether the luxS gene might affect the ability of Salmonella enterica serovar Typhimurium to invade epithelial cells. No differences were found between the wild-type strain of S. Typhimurium, SL1344, and its isogenic luxS mutant with respect to the number and morphology of the membrane ruffles induced or their ability to invade epithelial cells. The dynamics of the ruffling process were also similar in the wild-type strain (SL1344) and the luxS mutant. Furthermore, comparing the Salmonella pathogenicity island 1 (SPI-1) type 3 secretion profiles of wild-type SL1344 and the luxS mutant by Western blotting and measuring the expression of a single-copy green fluorescent protein fusion to the prgH (an essential SPI-1 gene) promoter indicated that SPI-1 expression and activity are similar in the wild-type SL1344 and luxS mutant. Genetic deletion of luxS did not alter the virulence of S. Typhimurium in the mouse model, and therefore, it appears that luxS does not play a significant role in regulating invasion of Salmonella in vitro or in vivo.

scholarly journals TetR Family Transcriptional Regulator PccD Negatively Controls Propionyl Coenzyme A Assimilation in Saccharopolyspora erythraea

2017 ◽  
Vol 199 (20) ◽  
Author(s):  
Zhen Xu ◽  
Miaomiao Wang ◽  
Bang-Ce Ye
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Coenzyme A ◽  
Transcriptional Regulator ◽  
Fold Increase ◽  
Saccharopolyspora Erythraea ◽  
Wild Type ◽  
Content Type ◽  
Propionate Metabolism ◽  
Key Enzyme

ABSTRACT Propanol stimulates erythromycin biosynthesis by increasing the supply of propionyl coenzyme A (propionyl-CoA), a starter unit of erythromycin production in Saccharopolyspora erythraea. Propionyl-CoA is assimilated via propionyl-CoA carboxylase to methylmalonyl-CoA, an extender unit of erythromycin. We found that the addition of n-propanol or propionate caused a 4- to 16-fold increase in the transcriptional levels of the SACE_3398–3400 locus encoding propionyl-CoA carboxylase, a key enzyme in propionate metabolism. The regulator PccD was proved to be directly involved in the transcription regulation of the SACE_3398–3400 locus by EMSA and DNase I footprint analysis. The transcriptional levels of SACE_3398–3400 were upregulated 15- to 37-fold in the pccD gene deletion strain (ΔpccD) and downregulated 3-fold in the pccD overexpression strain (WT/pIB-pccD), indicating that PccD was a negative transcriptional regulator of SACE_3398–3400. The ΔpccD strain has a higher growth rate than that of the wild-type strain (WT) on Evans medium with propionate as the sole carbon source, whereas the growth of the WT/pIB-pccD strain was repressed. As a possible metabolite of propionate metabolism, methylmalonic acid was identified as an effector molecule of PccD and repressed its regulatory activity. A higher level of erythromycin in the ΔpccD strain was observed compared with that in the wild-type strain. Our study reveals a regulatory mechanism in propionate metabolism and suggests new possibilities for designing metabolic engineering to increase erythromycin yield. IMPORTANCE Our work has identified the novel regulator PccD that controls the expression of the gene for propionyl-CoA carboxylase, a key enzyme in propionyl-CoA assimilation in S. erythraea. PccD represses the generation of methylmalonyl-CoA through carboxylation of propionyl-CoA and reveals an effect on biosynthesis of erythromycin. This finding provides novel insight into propionyl-CoA assimilation, and extends our understanding of the regulatory mechanisms underlying the biosynthesis of erythromycin.

scholarly journals Characterization and Evaluation of a Salmonella enterica Serotype Senftenberg Mutant Created by Deletion of Virulence-Related Genes for Use as a Live Attenuated Vaccine

2016 ◽  
Vol 23 (10) ◽  
pp. 802-812 ◽  
Author(s):  
Nitin M. Kamble ◽  
John Hwa Lee
Keyword(s):  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Protective Efficacy ◽  
Control Group ◽  
Intestinal Loop ◽  
Wild Type ◽  
Exchange Method ◽  
Content Type

ABSTRACTNatural infections of chickens withSalmonella entericasubsp.entericaserovar Senftenberg (S.Senftenberg) are characterized by low-level intestinal invasiveness and insignificant production of antibodies. In this study, we investigated the potential effects oflonandcpxRgene deletions on the invasiveness ofS. Senftenberg into the intestinal epithelium of chickens and its ability to induce an immune response, conferring protection againstS. Senftenberg infection. With the allelic exchange method, we developed JOL1596 (Δlon), JOL1571 (ΔcpxR), and JOL1587 (ΔlonΔcpxR) deletion mutants from wild-typeS. Senftenberg. Deletion of thelongene fromS. Senftenberg produced increased frequency of elongated cells, with significantly greater amounts of exopolysaccharide (EPS) than in thecpxR-deleted strain and the wild-type strain. Thein vivointestinal loop invasion assay showed a significant increase in epithelial invasiveness for JOL1596 (Δlon) and JOL1587 (ΔlonΔcpxR), compared to JOL1571 (ΔcpxR) and the wild-type strain. Furthermore, theS. Senftenberg wild-type and mutant strains were internalized at high levels inside activated abdominal macrophages from chicken. Thein vivoinoculation of JOL1587 (ΔlonΔcpxR) into chickens led to colonization of the liver, spleen, and cecum for a short time. Chickens inoculated with JOL1587 (ΔlonΔcpxR) showed significant increases in humoral, mucosal, and cellular immune responses specific toS. Senftenberg antigens. Postchallenge, compared to the control group, the JOL1587 (ΔlonΔcpxR)-inoculated chickens showed not only lower persistence but also faster clearance of wild-typeS. Senftenberg from the cecum. We conclude that the increased intestinal invasiveness and colonization of internal organs exhibited by JOL1587 (ΔlonΔcpxR) led to the establishment of immunogenicity and conferred protective efficacy againstS. Senftenberg infections in chickens.

scholarly journals Invasion Genes Are Not Required for Salmonella enterica Serovar Typhimurium To Breach the Intestinal Epithelium: Evidence That Salmonella Pathogenicity Island 1 Has Alternative Functions during Infection

2000 ◽  
Vol 68 (9) ◽  
pp. 5050-5055 ◽  
Author(s):  
Rose Ann Murray ◽  
Catherine A. Lee
Keyword(s):  
Intestinal Epithelium ◽  
Salmonella Enterica ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Colonization ◽  
Intestinal Barrier ◽  
Pathogenicity Island ◽  
Bacterial Invasion ◽  
Wild Type ◽  
Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium invasion genes are necessary for bacterial invasion of intestinal epithelial cells and are thought to allow salmonellae to enter and cross the intestinal epithelium during infection. Many invasion genes are encoded on Salmonella pathogenicity island 1 (SPI1), and their expression is activated by HilA, a transcription factor also encoded on SPI1. We have studied the role ofSalmonella invasion genes during infection of mice following intragastric inoculation. We have found that strains containing a mutation in hilA orinvG were recovered from the intestinal contents, intestinal tissues, and systemic tissues at a lower frequency than their parental wild-type strain. In contrast, a strain in which SPI1 is deleted was recovered from infected mice at a frequency similar to that of its parental wild-type strain. The ΔSPI1 phenotype indicates that S. enterica does not require invasion genes to cross the intestinal epithelium and infect systemic tissues. This result has forced us to reconsider the long-held belief that invasion genes directly mediate bacterial infection of the intestinal mucosa and traversion of the intestinal barrier during infection. Instead, our results suggest that hilA is required for bacterial colonization of the host intestine. The seemingly contradictory phenotype of the ΔSPI1 mutant suggests that deletion of another gene(s) encoded on SPI1 suppresses thehilA mutant defect. We propose a model for S. enterica pathogenesis in which hilA and invasion genes are required for salmonellae to overcome a host clearance response elicited by another SPI1 gene product(s).

scholarly journals Isolation and Characterization of Methanobacterium thermoautotrophicum ΔH Mutants Unable To Grow under Hydrogen-Deprived Conditions

1998 ◽  
Vol 180 (10) ◽  
pp. 2676-2681 ◽  
Author(s):  
Jeroen L. A. Pennings ◽  
Jan T. Keltjens ◽  
Godfried D. Vogels
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Random Mutagenesis ◽  
Methanobacterium Thermoautotrophicum ◽  
Mrna Levels ◽  
Wild Type ◽  
Physiological Characterization ◽  
Isolation And Characterization ◽  
Hydrogen Supply ◽  
In The Wild

ABSTRACT By using random mutagenesis and enrichment by chemostat culturing, we have developed mutants of Methanobacterium thermoautotrophicum that were unable to grow under hydrogen-deprived conditions. Physiological characterization showed that these mutants had poorer growth rates and growth yields than the wild-type strain. The mRNA levels of several key enzymes were lower than those in the wild-type strain. A fed-batch study showed that the expression levels were related to the hydrogen supply. In one mutant strain, expression of both methyl coenzyme M reductase isoenzyme I and coenzyme F420-dependent 5,10-methylenetetrahydromethanopterin dehydrogenase was impaired. The strain was also unable to form factor F390, lending support to the hypothesis that the factor functions in regulation of methanogenesis in response to changes in the availability of hydrogen.

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