scholarly journals 1-Methylguanosine-Deficient tRNA of Salmonella enterica Serovar Typhimurium Affects Thiamine Metabolism

2003 ◽  
Vol 185 (3) ◽  
pp. 750-759 ◽  
Author(s):  
Glenn R. Björk ◽  
Kristina Nilsson
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Slow Growth ◽  
Carbon Sources ◽  
Gene Mutations ◽  
Gene Encoding ◽  
Translation Fidelity ◽  
Serovar Typhimurium ◽  
Purine Pathway ◽  
The Common

ABSTRACT In Salmonella enterica serovar Typhimurium a mutation in the purF gene encoding the first enzyme in the purine pathway blocks, besides the synthesis of purine, the synthesis of thiamine when glucose is used as the carbon source. On carbon sources other than glucose, a purF mutant does not require thiamine, since the alternative pyrimidine biosynthetic (APB) pathway is activated. This pathway feeds into the purine pathway just after the PurF biosynthetic step and upstream of the intermediate 4-aminoimidazolribotide, which is the common intermediate in purine and thiamine synthesis. The activity of this pathway is also influenced by externally added pantothenate. tRNAs from S. enterica specific for leucine, proline, and arginine contain 1-methylguanosine (m1G37) adjacent to and 3′ of the anticodon (position 37). The formation of m1G37 is catalyzed by the enzyme tRNA(m1G37)methyltransferase, which is encoded by the trmD gene. Mutations in this gene, which result in an m1G37 deficiency in the tRNA, in a purF mutant mediate PurF-independent thiamine synthesis. This phenotype is specifically dependent on the m1G37 deficiency, since several other mutations which also affect translation fidelity and induce slow growth did not cause PurF-independent thiamine synthesis. Some antibiotics that are known to reduce the efficiency of translation also induce PurF-independent thiamine synthesis. We suggest that a slow decoding event at a codon(s) read by a tRNA(s) normally containing m1G37 is responsible for the PurF-independent thiamine synthesis and that this event causes a changed flux in the APB pathway.

scholarly journals Aspartic Peptide Hydrolases in Salmonella enterica Serovar Typhimurium

2001 ◽  
Vol 183 (10) ◽  
pp. 3089-3097 ◽  
Author(s):  
Rachel A. Larsen ◽  
Tina M. Knox ◽  
Charles G. Miller
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Gene Encoding ◽  
E Coli ◽  
Mutant Strains ◽  
Serovar Typhimurium ◽  
Measurable Rate ◽  
Mature Enzyme ◽  
Aminopeptidase A ◽  
Peptide Hydrolases

ABSTRACT Two well-characterized enzymes in Salmonella entericaserovar Typhimurium and Escherichia coli are able to hydrolyze N-terminal aspartyl (Asp) dipeptides: peptidase B, a broad-specificity aminopeptidase, and peptidase E, an Asp-specific dipeptidase. A serovar Typhimurium strain lacking both of these enzymes, however, can still utilize most N-terminal Asp dipeptides as sources of amino acids, and extracts of such a strain contain additional enzymatic activities able to hydrolyze Asp dipeptides. Here we report two such activities from extracts of pepB pepEmutant strains of serovar Typhimurium identified by their ability to hydrolyze Asp-Leu. Although each of these activities hydrolyzes Asp-Leu at a measurable rate, the preferred substrates for both are N-terminal isoAsp peptides. One of the activities is a previously characterized isoAsp dipeptidase from E. coli, the product of theiadA gene. The other is the product of the serovar Typhimurium homolog of E. coli ybiK, a gene of previously unknown function. This gene product is a member of the N-terminal nucleophile structural family of amidohydrolases. Like most other members of this family, the mature enzyme is generated from a precursor protein by proteolytic cleavage and the active enzyme is a heterotetramer. Based on its ability to hydrolyze an N-terminal isoAsp tripeptide as well as isoAsp dipeptides, the enzyme appears to be an isoAsp aminopeptidase, and we propose that the gene encoding it be designated iaaA (isoAsp aminopeptidase). A strain lacking both IadA and IaaA in addition to peptidase B and peptidase E has been constructed. This strain utilizes Asp-Leu as a leucine source, and extracts of this strain contain at least one additional, as-yet-uncharacterized, peptidase able to cleave Asp dipeptides.

scholarly journals Propionyl Coenzyme A Is a Common Intermediate in the 1,2-Propanediol and Propionate Catabolic Pathways Needed for Expression of the prpBCDE Operon during Growth of Salmonella enterica on 1,2-Propanediol

2003 ◽  
Vol 185 (9) ◽  
pp. 2802-2810 ◽  
Author(s):  
Sergio Palacios ◽  
Vincent J. Starai ◽  
Jorge C. Escalante-Semerena
Keyword(s):  
Salmonella Enterica ◽  
Coenzyme A ◽  
Regulatory Protein ◽  
Wild Type ◽  
Gene Encoding ◽  
Catabolic Pathways ◽  
Serovar Typhimurium ◽  
The Common ◽  
High Concentrations ◽  
Methylcitrate Synthase

ABSTRACT The studies reported here identify propionyl coenzyme A (propionyl-CoA) as the common intermediate in the 1,2-propanediol and propionate catabolic pathways of Salmonella enterica serovar Typhimurium LT2. Growth on 1,2-propanediol as a carbon and energy source led to the formation and excretion of propionate, whose activation to propionyl-CoA relied on the activities of the propionate kinase (PduW)/phosphotransacetylase (Pta) enzyme system and the CobB sirtuin-controlled acetyl-CoA and propionyl-CoA (Acs, PrpE) synthetases. The different affinities of these systems for propionate ensure sufficient synthesis of propionyl-CoA to support wild-type growth of S. enterica under low or high concentrations of propionate in the environment. These redundant systems of propionyl-CoA synthesis are needed because the prpE gene encoding the propionyl-CoA synthetase enzyme is part of the prpBCDE operon under the control of the PrpR regulatory protein, which needs 2-methylcitrate as a coactivator. Because the synthesis of 2-methylcitrate by PrpC (i.e., the 2-methylcitrate synthase enzyme) requires propionyl-CoA as a substrate, the level of propionyl-CoA needs to be raised by the Acs or PduW-Pta system before 2-methylcitrate can be synthesized and prpBCDE transcription can be activated.

scholarly journals opdA, a Salmonella enterica Serovar Typhimurium Gene Encoding a Protease, Is Part of an Operon Regulated by Heat Shock

2000 ◽  
Vol 182 (2) ◽  
pp. 518-521 ◽  
Author(s):  
Christopher A. Conlin ◽  
Charles G. Miller
Keyword(s):  
Escherichia Coli ◽  
Heat Shock ◽  
Sigma Factor ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Temperature Shift ◽  
Open Reading Frame ◽  
Gene Encoding ◽  
Reading Frame ◽  
Serovar Typhimurium

ABSTRACT The opdA (prlC) gene of Salmonella enterica serovar Typhimurium and Escherichia coliencodes the metalloprotease oligopeptidase A (OpdA). We report thatopdA is cotranscribed with a downstream open reading frame,yhiQ. Transcription of this operon is induced after a temperature shift (30 to 42°C), and this induction depends on the heat shock sigma factor encoded by the rpoH(htpR) gene.

Characterization of the micA gene encoding a small regulatory σE-dependent RNA in Salmonella enterica serovar Typhimurium

2011 ◽  
Vol 56 (1) ◽  
pp. 59-65 ◽  
Author(s):  
D. Homerova ◽  
B. Rezuchova ◽  
A. Stevenson ◽  
H. Skovierova ◽  
M. Roberts ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Gene Encoding ◽  
Mica Gene ◽  
Serovar Typhimurium

scholarly journals Type 1 Fimbriae of Salmonella enterica Serovar Typhimurium Bind to Enterocytes and Contribute to Colonization of Swine In Vivo

2003 ◽  
Vol 71 (11) ◽  
pp. 6446-6452 ◽  
Author(s):  
Carrie Althouse ◽  
Sheila Patterson ◽  
Paula Fedorka-Cray ◽  
Richard E. Isaacson
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase Variation ◽  
Gene Encoding ◽  
Type 1 Fimbriae ◽  
Systemic Spread ◽  
Serovar Typhimurium ◽  
Asymptomatic Infections

ABSTRACT Salmonella enterica serovar Typhimurium strain 798 is a clinical isolate from a pig and is known to be able to cause persistent, asymptomatic infections. This strain also is known to exist in two phenotypes (adhesive and nonadhesive to enterocytes) and can switch between the two phenotypes at a rate consistent with phase variation. Cells in the adhesive phenotype are more readily phagocytosed by leukocytes than nonadhesive cells. Once in a leukocyte, adhesive-phase cells survive while nonadhesive-phase cells die. In the present study, nonadhesive mutants were obtained with the transposon TnphoA. A nonadhesive mutant was selected for study and was shown by electron microscopy not to produce fimbriae. The gene encoding the adhesin was cloned and sequenced. Based on its sequence, the adhesin was shown to be FimA, the major subunit of type 1 fimbriae. The nonadhesive mutant was attenuated in its ability to colonize both mouse and pig intestines, but remained capable of systemic spread in mice. The nonadhesive mutant was phagocytosed to the same extent as parental cells in the adhesive phase and then survived intracellularly. These results demonstrated that type 1 fimbriae were important for attachment to enterocytes and promoted intestinal colonization. However, they were not important in promoting phagocytosis or intracellular survival.

scholarly journals Pigeon-Associated Strains of Salmonella enterica Serovar Typhimurium Phage Type DT2 Have Genomic Rearrangements at rRNA Operons

2004 ◽  
Vol 72 (12) ◽  
pp. 7338-7341 ◽  
Author(s):  
R. Allen Helm ◽  
Steffen Porwollik ◽  
April E. Stanley ◽  
Stanley Maloy ◽  
Michael McClelland ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phage Type ◽  
Laboratory Strain ◽  
Genomic Rearrangements ◽  
Serovar Typhimurium ◽  
The Common ◽  
Genomic Anomalies ◽  
Common Laboratory

ABSTRACT Strains from a subgroup of Salmonella enterica serovar Typhimurium frequently associated with pigeon infections were tested for genomic anomalies and virulence in mice. Some strains have a genomic inversion between rrn operons. Two prophages found in the common laboratory strain LT2 were absent. Pigeon-associated strains are still virulent in mice.

scholarly journals pfs-Dependent Regulation of Autoinducer 2 Production in Salmonella enterica Serovar Typhimurium

2002 ◽  
Vol 184 (13) ◽  
pp. 3450-3456 ◽  
Author(s):  
Anne L. Beeston ◽  
Michael G. Surette
Keyword(s):  
Gene Product ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Regulation Of Gene Expression ◽  
Carbon Sources ◽  
Homoserine Lactone ◽  
Bacterial Cells ◽  
Autoinducer 2 ◽  
Serovar Typhimurium ◽  
Signal Synthesis

ABSTRACT Bacterial intercellular communication provides a mechanism for signal-dependent regulation of gene expression to promote coordinated population behavior. Salmonella enterica serovar Typhimurium produces a non-homoserine lactone autoinducer in exponential phase as detected by a Vibrio harveyi reporter assay for autoinducer 2 (AI-2) (M. G. Surette and B. L. Bassler, Proc. Natl. Acad. Sci. USA 95:7046-7050, 1998). The luxS gene product mediates the production of AI-2 (M. G. Surette, M. B. Miller, and B. L. Bassler, Proc. Natl. Acad. Sci. USA 96:1639-1644, 1999). Environmental cues such as rapid growth, the presence of preferred carbon sources, low pH, and/or high osmolarity were found to influence the production of AI-2 (M. G. Surette and B. L. Bassler, Mol. Microbiol. 31:585-595, 1999). In addition to LuxS, the pfs gene product (Pfs) is required for AI-2 production, as well as S-adenosylhomocysteine (SAH) (S. Schauder, K. Shokat, M. G. Surette, and B. L. Bassler, Mol. Microbiol. 41:463-476, 2001). In bacterial cells, Pfs exhibits both 5′-methylthioadenosine (MTA) and SAH nucleosidase functions. Pfs is involved in methionine metabolism, regulating intracellular MTA and SAH levels (elevated levels of MTA and SAH are potent inhibitors of polyamine synthetases and S-adenosylmethionine dependent methyltransferase reactions, respectively). To further investigate regulation of AI-2 production in Salmonella, we constructed pfs and luxS promoter fusions to a luxCDABE reporter in a low-copy-number vector, allowing an examination of transcription of the genes in the pathway for signal synthesis. Here we report that luxS expression is constitutive but that the transcription of pfs is tightly correlated to AI-2 production in Salmonella serovar Typhimurium 14028. Neither luxS nor pfs expression appears to be regulated by AI-2. These results suggest that AI-2 production is regulated at the level of LuxS substrate availability and not at the level of luxS expression. Our results indicate that AI-2-dependent signaling is a reflection of metabolic state of the cell and not cell density.

The expression of the rpoE operon is fine-tuned by the internal rseAp promoter in Salmonella enterica serovar Typhimurium

Biologia ◽  
2010 ◽  
Vol 65 (6) ◽  
Author(s):  
Dagmar Homerova ◽  
Bronislava Rezuchova ◽  
Henrieta Skovierova ◽  
Jan Kormanec
Keyword(s):  
Sigma Factor ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Consensus Sequence ◽  
Coding Region ◽  
Gene Encoding ◽  
In Vivo Experiments ◽  
Envelope Stress ◽  
Serovar Typhimurium

AbstractThree promoters, located upstream of the rpoE gene encoding an extracytoplasmic sigma factor σ E, direct expression of the rpoE operon (rpoE, rseA, rseB, rseC) in Salmonella enterica serovar Typhimurium (S. Typhimurium). One of them, rpoEp3, has been found to be directly recognized by RNA polymerase containing sigma factor σ E. Using the Northern blot analysis we detected a complex pattern of transcripts indicating an internal promoter in the coding region of the rpoE gene. The promoter, rseAp, has been located by S1 mapping analysis. Its proposed −10 and −35 elements with 15 intervening nucleotides exhibited high similarity with the consensus sequence of σ E promoters, suggesting the direct dependence of rseAp upon σ E. Activity of rseAp increased towards stationary phase, after heat shock, cold shock, and in the presence of artificially induced rpoE expression, the conditions previously shown to activate σ E-dependent promoters. In vivo experiments revealed increase of the rseAp activity during growth and confirmed its clear dependence upon σ E. The proposed role of the internal rseAp promoter is to facilitate a feedback control of σ E level after the envelope stress is removed.

Detoxification of nitric oxide by the flavorubredoxin of Salmonella enterica serovar Typhimurium

2005 ◽  
Vol 33 (1) ◽  
pp. 198-199 ◽  
Author(s):  
P.C. Mills ◽  
D.J. Richardson ◽  
J.C.D. Hinton ◽  
S. Spiro
Keyword(s):  
Nitric Oxide ◽  
Nitrous Oxide ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Mutant Phenotype ◽  
Wild Type ◽  
Anaerobic Conditions ◽  
Gene Encoding ◽  
Serovar Typhimurium ◽  
Oxygen Sensitive

Salmonella possesses multiple enzymes that utilize NO as a substrate, and could therefore contribute to the organism's ability to resist nitrosative killing by macrophages. Flavorubredoxin is an oxygen-sensitive enzyme that reduces NO to nitrous oxide. The Salmonella enterica serovar Typhimurium norV gene encoding flavorubredoxin was disrupted and the NO sensitivity of the mutant was determined. The norV mutant showed a greater sensitivity to NO than wild-type S. Typhimurium, but did recover growth after a transient inhibition. The mutant phenotype suggests that multiple enzymes are employed by S. Typhimurium to detoxify NO under anaerobic conditions, one of which is flavorubredoxin.

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