scholarly journals Genetic Analysis of Colistin Resistance in Salmonella enterica Serovar Typhimurium

2009 ◽  
Vol 53 (6) ◽  
pp. 2298-2305 ◽  
Author(s):  
Song Sun ◽  
Aurel Negrea ◽  
Mikael Rhen ◽  
Dan I. Andersson
Keyword(s):  
Mutation Rate ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Clinical Settings ◽  
Missense Mutations ◽  
Regulator Protein ◽  
Serovar Typhimurium ◽  
Sensor Kinases ◽  
Genes Encoding

ABSTRACT Colistin is a cyclic cationic peptide that kills gram-negative bacteria by interacting with and disrupting the outer membrane. We isolated 44 independent mutants in Salmonella enterica serovar Typhimurium with reduced susceptibility to colistin and identified 27 different missense mutations located in the pmrA and pmrB genes (encoding the regulator and sensor of a two-component regulatory system) that conferred increased resistance. By comparison of the two homologous sensor kinases, PmrB and EnvZ, the 22 missense mutations identified in pmrB were shown to be located in four different structural domains of the protein. All five pmrA mutations were located in the phosphate receiver domain of the regulator protein. The mutants appeared at a mutation rate of 0.6 × 10−6 per cell per generation. The MICs of colistin for the mutants increased 2- to 35-fold, and the extent of killing was reduced several orders of magnitude compared to the susceptible strain. The growth rates of the mutants were slightly reduced in both rich medium and M9-glycerol minimal medium, whereas growth in mice appeared unaffected by the pmrA and pmrB mutations. The low fitness costs and the high mutation rate suggest that mutants with reduced susceptibility to colistin could emerge in clinical settings.

scholarly journals CadC Has a Global Translational Effect during Acid Adaptation in Salmonella enterica Serovar Typhimurium

2007 ◽  
Vol 189 (6) ◽  
pp. 2417-2425 ◽  
Author(s):  
Yong Heon Lee ◽  
Bae Hoon Kim ◽  
Ji Hye Kim ◽  
Won Suck Yoon ◽  
Seong Ho Bang ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Acid Tolerance ◽  
Negative Influence ◽  
Acid Adaptation ◽  
Proteomic Approach ◽  
Serovar Typhimurium ◽  
Tolerance Response ◽  
Porin Proteins

ABSTRACT In Salmonella enterica serovar Typhimurium, the membrane-localized CadC is a transcriptional activator of the cadBA operon, which contributes to the acid tolerance response. Unlike in Escherichia coli, in which transcription of cadC is constitutive, in S. enterica serovar Typhimurium cadC expression is induced by low pH and lysine. Inactivation of cadC suppresses the acid-sensitive phenotype of a cadA mutation, suggesting the existence of other CadC-dependent genes in addition to the cadBA operon. Using a proteomic approach, we identified 8 of the putative CadC-induced proteins and 15 of the putative CadC-repressed proteins. The former include porin proteins OmpC and OmpF. The latter include proteins involved in glycolysis, energy production, and stress tolerance. To better understand the altered levels of OmpC and OmpF, we compared expression of ompR in S. enterica serovar Typhimurium wild-type and cadC mutant strains and determined that CadC exerted a negative influence on ompR transcription. Taken together, our findings strongly suggest that CadC may be a global regulator involved in the OmpR regulatory system during acid adaptation.

Influence of RpoS, cAMP-receptor protein, and ppGpp on expression of the opgGH operon and osmoregulated periplasmic glucan content of Salmonella enterica serovar Typhimurium

2009 ◽  
Vol 55 (11) ◽  
pp. 1284-1293 ◽  
Author(s):  
Cristina S. Costa ◽  
Ramón A. Pizarro ◽  
Dora N. Antón
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Receptor Protein ◽  
Transcriptional Level ◽  
Camp Receptor Protein ◽  
High Osmolarity ◽  
Serovar Typhimurium ◽  
Camp Receptor ◽  
Periplasmic Glucan

A transcriptional fusion (opgG1::MudJ) to the opgGH operon of Salmonella enterica serovar Typhimurium (S. Typhimurium) LT2, isolated by resistance to mecillinam, was used to study the influence of global regulators RpoS, ppGpp, and cAMP/cAMP-receptor protein (CRP) on expression of the opgGH operon and osmoregulated periplasmic glucan (OPG) content. Neither high growth medium osmolarity nor absence of ppGpp or CRP had important effects on opgG1::MudJ expression in exponential cultures. However, under the same conditions, OPG content was strongly decreased by high osmolarity or cAMP/CRP defectiveness, and reduced to a half by lack of ppGpp. In stationary cultures, high osmolarity as well as CRP loss caused significant descents in opgG1::MudJ expression that were compensated by inactivation of RpoS σ factor. No effect of RpoS inactivation on OPG content was observed. It is concluded that opgGH expression in S. Typhimurium is only slightly affected by high osmolarity, but is inversely modulated by RpoS level. On the other hand, osmolarity and the cAMP/CRP global regulatory system appear to control OPG content, either directly or indirectly, mainly at the post-transcriptional level.

scholarly journals Alteration of the Rugose Phenotype in waaG and ddhC Mutants of Salmonella enterica Serovar Typhimurium DT104 Is Associated with Inverse Production of Curli and Cellulose

2006 ◽  
Vol 72 (7) ◽  
pp. 5002-5012 ◽  
Author(s):  
Yuda Anriany ◽  
Surashri N. Sahu ◽  
Kimberly R. Wessels ◽  
Lindsay M. McCann ◽  
Sam W. Joseph
Keyword(s):  
Salmonella Enterica ◽  
Biofilm Formation ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Cell Aggregation ◽  
Scanning Electron Micrographs ◽  
Serovar Typhimurium ◽  
Potential Component ◽  
Matrix Production ◽  
Opposing Effects

ABSTRACT The rugose (also known as wrinkled or rdar) phenotype in Salmonella enterica serovar Typhimurium DT104 Rv has been associated with cell aggregation and the ability, at low temperature under low-osmolarity conditions, to form pellicles and biofilms. Two Tn5 insertion mutations in genes that are involved in lipopolysaccharide (LPS) synthesis, ddhC (A1-8) and waaG (A1-9), of Rv resulted in diminished expression of colony rugosity. Scanning electron micrographs revealed that the ddhC mutant showed reduced amounts of extracellular matrix, while there was relatively more, profuse matrix production in the waaG mutant, compared to Rv. Both mutants appeared to produce decreased levels of curli, as judged by Western blot assays probed with anti-AgfA (curli) antibodies but, surprisingly, were observed to have increased amounts of cellulose relative to Rv. Comparison with a non-curli-producing mutant suggested that the alteration in curli production may have engendered the increased presence of cellulose. While both mutants had impaired biofilm formation when grown in rich medium with low osmolarity, they constitutively formed larger amounts of biofilms when the growth medium was supplemented with either glucose or a combination of glucose and NaCl. These observations indicated that LPS alterations may have opposing effects on biofilm formation in these mutants, depending upon either the presence or the absence of these osmolytes. The phenotypes of the waaG mutant were further confirmed in a constructed, nonpolar deletion mutant of S. enterica serovar Typhimurium LT2, where restoration to the wild-type phenotypes was accomplished by complementation. These results highlight the importance of an integral LPS, at both the O-antigen and core polysaccharide levels, in the modulation of curli protein and cellulose production, as well as in biofilm formation, thereby adding another potential component to the complex regulatory system which governs multicellular behaviors in S. enterica serovar Typhimurium.

scholarly journals Role of the High-Affinity Zinc Uptake znuABC System in Salmonella enterica Serovar Typhimurium Virulence

2002 ◽  
Vol 70 (8) ◽  
pp. 4721-4725 ◽  
Author(s):  
Susana Campoy ◽  
Mónica Jara ◽  
Núria Busquets ◽  
Ana M. Pérez de Rozas ◽  
Ignacio Badiola ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Lethal Dose ◽  
Zinc Uptake ◽  
Uptake System ◽  
High Affinity ◽  
Knockout Mutants ◽  
Serovar Typhimurium ◽  
Genes Encoding

ABSTRACT The Salmonella enterica serovar Typhimurium znuABC genes encoding a high-affinity zinc uptake system and its regulatory zur gene have been cloned. Salmonella serovar Typhimurium zur and znuC knockout mutants have been constructed by marker exchange. The 50% lethal dose of the znuC mutant increased when either orally or intraperitoneally inoculated in BALB/c mice, while virulence of the zur mutant decreased only when mice were intraperitoneally challenged.

scholarly journals Contribution of the PhoP/Q regulon to survival and replication of Salmonella enterica serovar Typhimurium in macrophages

Microbiology ◽  
2011 ◽  
Vol 157 (7) ◽  
pp. 2084-2093 ◽  
Author(s):  
Jessica A. Thompson ◽  
Mei Liu ◽  
Sophie Helaine ◽  
David W. Holden
Keyword(s):  
Mutant Strain ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Systemic Disease ◽  
Hydrolytic Enzymes ◽  
Regulatory System ◽  
Murine Macrophages ◽  
Mutant Strains ◽  
Serovar Typhimurium

The ability of serovars of Salmonella enterica to cause systemic disease is dependent upon their survival and replication within macrophages. To do this, bacteria must withstand or surmount bacteriostatic and bactericidal responses by the host cell, including the delivery of hydrolytic enzymes from lysosomes to the phagosome. The bacterial two-component regulatory system PhoP/Q has been implicated in avoidance of phagolysosomal fusion by S. enterica serovar Typhimurium (S. Typhimurium) in murine macrophages. In this study, the involvement of PhoP/Q-activated genes in avoidance of phagolysosomal fusion was analysed: of all the S. Typhimurium mutant strains tested, only an mgtC mutant strain partially reproduced the phenotype of the phoP mutant strain. As this gene is required for bacterial growth in magnesium-depleted conditions in vitro, the contributions of PhoP/Q to intramacrophage replication and survival were reappraised. Although PhoP/Q was required for both replication and survival of S. Typhimurium within murine macrophages, subsequent analysis of the kinetics of phagolysosomal fusion, taking account of differences in the replication rates of wild-type and phoP mutant strains, provided no evidence for a PhoP/Q-dependent role in this process. PhoP/Q appeared to act subsequent to the process of phagolysosomal avoidance and to promote replication of those bacteria that had already escaped a phagolysosomal fate. Therefore, we conclude that the PhoP/Q regulon enables S. Typhimurium to adapt to intramacrophage stresses other than phagolysosomal fusion.

scholarly journals Salmonella enterica Serovar Typhimurium Periplasmic Superoxide Dismutase SodCI Is a Member of the PhoPQ Regulon and Is Induced in Macrophages

2006 ◽  
Vol 188 (22) ◽  
pp. 7853-7861 ◽  
Author(s):  
Yekaterina A. Golubeva ◽  
James M. Slauch
Keyword(s):  
Salmonella Enterica ◽  
Virulence Genes ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Differential Regulation ◽  
Superoxide Dismutases ◽  
High Level Expression ◽  
Fusion Strain ◽  
Serovar Typhimurium ◽  
High Level

ABSTRACT Salmonella enterica serovar Typhimurium replicates within host macrophages during the systemic stage of infection. In the macrophage, the bacteria must survive the respiratory burst that produces superoxide. Serovar Typhimurium strain 14028 produces two periplasmic superoxide dismutases, SodCI and SodCII, but only SodCI contributes to virulence. Although we have shown that this is primarily due to differences in the two proteins, evidence suggests differential regulation of the two genes. Using transcriptional sodCI- and sodCII-lac fusions, we show that sodCII is under the control of the RpoS sigma factor, as was known for the Escherichia coli ortholog, sodC. In contrast, we show that sodCI is transcriptionally controlled by the PhoPQ two-component regulatory system, which regulates an array of virulence genes required for macrophage survival. Introduction of a phoP-null mutation into the sodCI fusion strain resulted in a decrease in transcription and loss of regulation. The sodCI-lac fusion showed high-level expression in a background containing a phoQ constitutive allele. The sodCI gene is induced 15-fold in bacteria recovered from either the tissue culture macrophages or the spleens of infected mice. Induction in macrophages is dependent on PhoP. The sodCII fusion was induced three- to fourfold in macrophages and animals; this induction was unaffected by loss of PhoP. Thus, sodCI, which is horizontally transferred by the Gifsy-2 phage, is regulated by PhoPQ such that it is induced at the appropriate time and place to combat phagocytic superoxide.

scholarly journals The Salmonella enterica Serovar Typhimurium Divalent Cation Transport Systems MntH and SitABCD Are Essential for Virulence in an Nramp1G169 Murine Typhoid Model

2004 ◽  
Vol 72 (9) ◽  
pp. 5522-5525 ◽  
Author(s):  
Michelle L. Zaharik ◽  
Vivian Li Cullen ◽  
Angela M. Fung ◽  
Stephen J. Libby ◽  
Sonya L. Kujat Choy ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Metal Ion ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Divalent Cations ◽  
Systemic Infection ◽  
Transport Systems ◽  
Phagocytic Cells ◽  
Serovar Typhimurium ◽  
Genes Encoding ◽  
Metal Ion Uptake

ABSTRACT Nramp1 is a transporter that pumps divalent cations from the vacuoles of phagocytic cells and is associated with the innate resistance of mice to diverse intracellular pathogens. We demonstrate that sitA and mntH, genes encoding high-affinity metal ion uptake systems in Salmonella enterica serovar Typhimurium, are upregulated when Salmonella is internalized by Nramp1-expressing macrophages and play an essential role in systemic infection of congenic Nramp1-expressing mice.

scholarly journals The apeE Gene of Salmonella enterica Serovar Typhimurium Is Induced by Phosphate Limitation and Regulated by phoBR

2001 ◽  
Vol 183 (5) ◽  
pp. 1784-1786 ◽  
Author(s):  
Christopher A. Conlin ◽  
Seng L. Tan ◽  
Huajun Hu ◽  
Todd Segar
Keyword(s):  
Outer Membrane ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulatory System ◽  
Phosphate Transport ◽  
Phosphate Limitation ◽  
Regulatory Locus ◽  
High Affinity ◽  
Serovar Typhimurium ◽  
Operon Expression

ABSTRACT Mutations in apeR, a regulatory locus of the outer membrane esterase apeE from Salmonella entericaserovar Typhimurium, were shown to be alleles of thepstSCAB-phoU high-affinity phosphate transport operon. Expression of apeE was induced by phosphate limitation, and this induction required the phoBR phosphate regulatory system.

Sign in / Sign up

Export Citation Format

Share Document