scholarly journals LuxS Affects Flagellar Phase Variation Independently of Quorum Sensing in Salmonella enterica Serovar Typhimurium

2007 ◽  
Vol 190 (2) ◽  
pp. 769-771 ◽  
Author(s):  
M. H. Karavolos ◽  
D. M. Bulmer ◽  
K. Winzer ◽  
M. Wilson ◽  
P. Mastroeni ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase 1 ◽  
Phase Variation ◽  
Signaling Molecule ◽  
Autoinducer 2 ◽  
Serovar Typhimurium ◽  
Quorum Sensing Signals

ABSTRACT LuxS catalyzes the synthesis of the quorum-sensing signaling molecule autoinducer 2. We show that in Salmonella enterica serovar Typhimurium, deletion of the luxS gene polarizes flagellar phase variation toward the more immunogenic phase 1 flagellin. This phenotype is complementable by luxS in trans but is independent of quorum-sensing signals.

scholarly journals Quorum Sensing and Production of Autoinducer-2 in Campylobacter spp., Escherichia coli O157:H7, and Salmonella enterica Serovar Typhimurium in Foods

2002 ◽  
Vol 68 (9) ◽  
pp. 4666-4671 ◽  
Author(s):  
Orla M. Cloak ◽  
Barbara T. Solow ◽  
Connie E. Briggs ◽  
Chin-Yi Chen ◽  
Pina M. Fratamico
Keyword(s):  
Escherichia Coli ◽  
Quorum Sensing ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Campylobacter Coli ◽  
Gram Positive Bacteria ◽  
Autoinducer 2 ◽  
Chicken Broth ◽  
Serovar Typhimurium ◽  
Luminescence Assay

ABSTRACT Autoinducer molecules are utilized by gram-negative and gram-positive bacteria to regulate density-dependent gene expression by a mechanism known as quorum sensing. PCR and DNA sequencing results showed that Campylobacter jejuni and Campylobacter coli possessed luxS, which is responsible for autoinducer-2 (AI-2) production. Using a Vibrio harveyi luminescence assay, the production of AI-2 was observed in milk, chicken broth, and brucella broth by C. coli, C. jejuni, Salmonella enterica serovar Typhimurium, and Escherichia coli O157:H7 under different conditions.

scholarly journals Role of FimW, FimY, and FimZ in Regulating the Expression of Type I Fimbriae in Salmonella enterica Serovar Typhimurium

2009 ◽  
Vol 191 (9) ◽  
pp. 3003-3010 ◽  
Author(s):  
Supreet Saini ◽  
Jeffrey A. Pearl ◽  
Christopher V. Rao
Keyword(s):  
Gene Expression ◽  
Negative Feedback ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase Variation ◽  
Type I ◽  
Serovar Typhimurium ◽  
Type I Fimbriae ◽  
Positive And Negative Feedback

ABSTRACT Type I fimbriae in Salmonella enterica serovar Typhimurium are surface appendages that facilitate binding to eukaryotic cells. Expression of the fim gene cluster is known to be regulated by three proteins—FimW, FimY, and FimZ—and a tRNA encoded by fimU. In this work, we investigated how these proteins and tRNA coordinately regulate fim gene expression. Our results indicate that FimY and FimZ independently activate the P fimA promoter which controls the expression of the fim structural genes. FimY and FimZ were also found to strongly activate each other's expression and weakly activate their own expression. FimW was found to negatively regulate fim gene expression by repressing transcription from the P fimY promoter, independent of FimY or FimZ. Moreover, FimW and FimY interact within a negative feedback loop, as FimY was found to activate the P fimW promoter. In the case of fimU, the expression of this gene was not found to be regulated by FimW, FimY, or FimZ. We also explored the effect of fim gene expression on Salmonella pathogenicity island 1 (SPI1). Our results indicate that FimZ alone is able to enhance the expression of hilE, a known repressor of SPI1 gene expression. Based on our results, we were able to propose an integrated model for the fim gene circuit. As this model involves a combination of positive and negative feedback, we hypothesized that the response of this circuit may be bistable and thus a possible mechanism for phase variation. However, we found that the response was continuous and not bistable.

scholarly journals Two DNA Invertases Contribute to Flagellar Phase Variation in Salmonella enterica Serovar Typhimurium Strain LT2

2006 ◽  
Vol 188 (3) ◽  
pp. 950-957 ◽  
Author(s):  
Kazuhiro Kutsukake ◽  
Hisashi Nakashima ◽  
Akira Tominaga ◽  
Tatsuhiko Abo
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Genomic Sequence ◽  
Phase Variation ◽  
Disruption Mutant ◽  
Typhimurium Strain ◽  
Alternative Expression ◽  
Serovar Typhimurium

ABSTRACT Salmonella enterica serovar Typhimurium strain LT2 possesses two nonallelic structural genes, fliC and fljB, for flagellin, the component protein of flagellar filaments. Flagellar phase variation occurs by alternative expression of these two genes. This is controlled by the inversion of a DNA segment, called the H segment, containing the fljB promoter. H inversion occurs by site-specific recombination between inverted repetitious sequences flanking the H segment. This recombination has been shown in vivo and in vitro to be mediated by a DNA invertase, Hin, whose gene is located within the H segment. However, a search of the complete genomic sequence revealed that LT2 possesses another DNA invertase gene that is located adjacent to another invertible DNA segment within a resident prophage, Fels-2. Here, we named this gene fin. We constructed hin and fin disruption mutants from LT2 and examined their phase variation abilities. The hin disruption mutant could still undergo flagellar phase variation, indicating that Hin is not the sole DNA invertase responsible for phase variation. Although the fin disruption mutant could undergo phase variation, fin hin double mutants could not. These results clearly indicate that both Hin and Fin contribute to flagellar phase variation in LT2. We further showed that a phase-stable serovar, serovar Abortusequi, which is known to possess a naturally occurring hin mutation, lacks Fels-2, which ensures the phase stability in this serovar.

scholarly journals Effect of iacP Mutation on Flagellar Phase Variation in Salmonella enterica Serovar Typhimurium Strain UK-1

2012 ◽  
Vol 194 (16) ◽  
pp. 4332-4341 ◽  
Author(s):  
J. S. Eom ◽  
J. S. Kim ◽  
J. I. Jang ◽  
H. G. Kim ◽  
I.-S. Bang ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phase Variation ◽  
Typhimurium Strain ◽  
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 Synthesis of N-Acyl Homoserine Lactone Analogues Reveals Strong Activators of SdiA, the Salmonella enterica Serovar Typhimurium LuxR Homologue

2006 ◽  
Vol 73 (2) ◽  
pp. 535-544 ◽  
Author(s):  
Joost C. A. Janssens ◽  
Kristine Metzger ◽  
Ruth Daniels ◽  
Dave Ptacek ◽  
Tine Verhoeven ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Vibrio Fischeri ◽  
Acyl Chain ◽  
Homoserine Lactone ◽  
Gram Negative Bacteria ◽  
Ligand Interaction ◽  
Homoserine Lactones ◽  
Serovar Typhimurium

ABSTRACT N-Acyl homoserine lactones (AHLs) are molecules that are synthesized and detected by many gram-negative bacteria to monitor the population density, a phenomenon known as quorum sensing. Salmonella enterica serovar Typhimurium is an exceptional species since it does not synthesize its own AHLs, while it does encode a LuxR homologue, SdiA, which enables this bacterium to detect AHLs that are produced by other species. To obtain more information about the specificity of the ligand binding by SdiA, we synthesized and screened a limited library of AHL analogues. We identified two classes of analogues that are strong activators of SdiA: the N-(3-oxo-acyl)-homocysteine thiolactones (3O-AHTLs) and the N-(3-oxo-acyl)-trans-2-aminocyclohexanols. To our knowledge, this is the first report of compounds (the 3O-AHTLs) that are able to activate a LuxR homologue at concentrations that are lower than the concentrations of the most active AHLs. SdiA responds with greatest sensitivity to AHTLs that have a keto modification at the third carbon atom and an acyl chain that is seven or eight carbon atoms long. The N-(3-oxo-acyl)-trans-2-aminocyclohexanols were found to be less sensitive to deactivation by lactonase and alkaline pH than the 3O-AHTLs and the AHLs are. We also examined the activity of our library with LuxR of Vibrio fischeri and identified three new inhibitors of LuxR. Finally, we performed preliminary binding experiments which suggested that SdiA binds its activators reversibly. These results increase our understanding of the specificity of the SdiA-ligand interaction, which could have uses in the development of anti-quorum-sensing-based antimicrobials.

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.

Sign in / Sign up

Export Citation Format

Share Document