scholarly journals Salmonella enterica Serovar Gallinarum Requires ppGpp for Internalization and Survival in Animal Cells

2008 ◽  
Vol 190 (19) ◽  
pp. 6340-6350 ◽  
Author(s):  
Jae-Ho Jeong ◽  
Miryoung Song ◽  
Sang-Ik Park ◽  
Kyoung-Oh Cho ◽  
Joon Haeng Rhee ◽  
...  
Keyword(s):  
Growth Phase ◽  
Salmonella Enterica ◽  
Animal Cell ◽  
Growth Conditions ◽  
Exponential Growth Phase ◽  
Low Oxygen ◽  
Intracellular Growth ◽  
Animal Cells ◽  
Cell Internalization ◽  
Serovar Typhimurium

ABSTRACT To elucidate the pathogenic mechanism of Salmonella enterica serovar Gallinarum, we examined the expression of the genes encoded primarily in Salmonella pathogenicity island 1 (SPI-1) and SPI-2. These genes were found to be induced as cultures entered stationary phase under high- and low-oxygen growth conditions, as also observed for Salmonella serovar Typhimurium. In contrast, Salmonella serovar Gallinarum in the exponential growth phase most efficiently internalized cultured animal cells. Analysis of mutants defective in SPI-1 genes, SPI-2 genes, and others implicated in early stages of infection revealed that SPI-1 genes were not involved in the internalization of animal cells by Salmonella serovar Gallinarum. Following entry, however, Salmonella serovar Gallinarum was found to reside in LAMP1-positive vacuoles in both phagocytic and nonphagocytic cells, although internalization was independent of SPI-1. A mutation that conferred defects in ppGpp synthesis was the only one found to affect animal cell internalization by Salmonella serovar Gallinarum. It was concluded that Salmonella serovar Gallinarum internalizes animal cells by a mechanism independent of SPI-1 genes but dependent on ppGpp. Intracellular growth also required ppGpp for the transcription of genes encoded in SPI-2.

scholarly journals pH-, Lactic Acid-, and Non-Lactic Acid-Dependent Activities of Probiotic Lactobacilli against Salmonella enterica Serovar Typhimurium

2005 ◽  
Vol 71 (10) ◽  
pp. 6008-6013 ◽  
Author(s):  
Domitille Fayol-Messaoudi ◽  
Cédric N. Berger ◽  
Marie-Hélène Coconnier-Polter ◽  
Vanessa Liévin-Le Moal ◽  
Alain L. Servin
Keyword(s):  
Lactic Acid ◽  
Growth Phase ◽  
Salmonella Enterica ◽  
Lactobacillus Rhamnosus ◽  
Stationary Growth Phase ◽  
Exponential Growth Phase ◽  
Killing Activity ◽  
Serovar Typhimurium ◽  
Probiotic Strains ◽  
Probiotic Lactobacilli

ABSTRACT The mechanism(s) underlying the antibacterial activity of probiotic Lactobacillus strains appears to be multifactorial and includes lowering of the pH and the production of lactic acid and of antibacterial compounds, including bacteriocins and nonbacteriocin, non-lactic acid molecules. Addition of Dulbecco's modified Eagle's minimum essential medium to the incubating medium delays the killing activity of lactic acid. We found that the probiotic strains Lactobacillus johnsonii La1, Lactobacillus rhamnosus GG, Lactobacillus casei Shirota YIT9029, L. casei DN-114 001, and L. rhamnosus GR1 induced a dramatic decrease in the viability of Salmonella enterica serovar Typhimurium SL1344 mainly attributable to non-lactic acid molecule(s) present in the cell-free culture supernatant (CFCS). These molecules were more active against serovar Typhimurium SL1344 in the exponential growth phase than in the stationary growth phase. We also showed that the production of the non-lactic acid substance(s) responsible for the killing activity was dependent on growth temperature and that both unstable and stable substances with killing activity were present in the CFCSs. We found that the complete inhibition of serovar Typhimurium SL1344 growth results from a pH-lowering effect.

scholarly journals A network of Rab GTPases controls phagosome maturation and is modulated by Salmonella enterica serovar Typhimurium

2007 ◽  
Vol 176 (3) ◽  
pp. 263-268 ◽  
Author(s):  
Adam C. Smith ◽  
Won Do Heo ◽  
Virginie Braun ◽  
Xiuju Jiang ◽  
Chloe Macrae ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Dominant Negative ◽  
Rab Gtpases ◽  
Wild Type ◽  
Intracellular Growth ◽  
Non Invasive ◽  
Serovar Typhimurium ◽  
Guanosine Triphosphatase ◽  
Kinetics Of

Members of the Rab guanosine triphosphatase (GTPase) family are key regulators of membrane traffic. Here we examined the association of 48 Rabs with model phagosomes containing a non-invasive mutant of Salmonella enterica serovar Typhimurium (S. Typhimurium). This mutant traffics to lysosomes and allowed us to determine which Rabs localize to a maturing phagosome. In total, 18 Rabs associated with maturing phagosomes, each with its own kinetics of association. Dominant-negative mutants of Rab23 and 35 inhibited phagosome–lysosome fusion. A large number of Rab GTPases localized to wild-type Salmonella-containing vacuoles (SCVs), which do not fuse with lysosomes. However, some Rabs (8B, 13, 23, 32, and 35) were excluded from wild-type SCVs whereas others (5A, 5B, 5C, 7A, 11A, and 11B) were enriched on this compartment. Our studies demonstrate that a complex network of Rab GTPases controls endocytic progression to lysosomes and that this is modulated by S. Typhimurium to allow its intracellular growth.

Integration host factor alleviates H-NS silencing of the Salmonella enterica serovar Typhimurium master regulator of SPI1, hilA

Microbiology ◽  
2011 ◽  
Vol 157 (9) ◽  
pp. 2504-2514 ◽  
Author(s):  
Mário H. Queiroz ◽  
Cristina Madrid ◽  
Sònia Paytubi ◽  
Carlos Balsalobre ◽  
Antonio Juárez
Keyword(s):  
Stationary Phase ◽  
Salmonella Enterica ◽  
Growth Conditions ◽  
Integration Host Factor ◽  
Band Shift ◽  
Global Regulators ◽  
Serovar Typhimurium ◽  
Associated Proteins ◽  
Transcription Data

Coordination of the expression of Salmonella enterica invasion genes on Salmonella pathogenicity island 1 (SPI1) depends on a complex circuit involving several regulators that converge on expression of the hilA gene, which encodes a transcriptional activator (HilA) that modulates expression of the SPI1 virulence genes. Two of the global regulators that influence hilA expression are the nucleoid-associated proteins Hha and H-NS. They interact and form a complex that modulates gene expression. A chromosomal transcriptional fusion was constructed to assess the effects of these modulators on hilA transcription under several environmental conditions as well as at different stages of growth. The results obtained showed that these proteins play a role in silencing hilA expression at both low temperature and low osmolarity, irrespective of the growth phase. H-NS accounts for the main repressor activity. At high temperature and osmolarity, H-NS-mediated silencing completely ceases when cells enter the stationary phase, and hilA expression is induced. Mutants lacking IHF did not induce hilA in cells entering the stationary phase, and this lack of induction was dependent on the presence of H-NS. Band-shift assays and in vitro transcription data showed that for hilA induction under certain growth conditions, IHF is required to alleviate H-NS-mediated silencing.

scholarly journals H-NS Represses Salmonella enterica Serovar Typhimurium dsbA Expression during Exponential Growth

2004 ◽  
Vol 186 (4) ◽  
pp. 910-918 ◽  
Author(s):  
C. V. Gallant ◽  
T. Ponnampalam ◽  
H. Spencer ◽  
J. C. D. Hinton ◽  
N. L. Martin
Keyword(s):  
Exponential Growth ◽  
Salmonella Enterica ◽  
Immunoblot Analysis ◽  
Exponential Phase ◽  
Exponential Growth Phase ◽  
Mobility Shift ◽  
Altered Expression ◽  
Serovar Typhimurium ◽  
In The Wild ◽  
Maximal Expression

ABSTRACT Disulfide bond formation catalyzed by disulfide oxidoreductases occurs in the periplasm and plays a major role in the proper folding and integrity of many proteins. In this study, we were interested in elucidating factors that influence the regulation of dsbA, a gene coding for the primary disulfide oxidoreductase found in Salmonella enterica serovar Typhimurium. Strains with mutations created by transposon mutagenesis were screened for strains with altered expression of dsbA. A mutant (NLM2173) was found where maximal expression of a dsbA::lacZ transcriptional fusion occurred in the exponential growth phase in contrast to that observed in the wild type where maximal expression occurs in stationary phase. Sequence analysis of NLM2173 demonstrated that the transposon had inserted upstream of the gene encoding H-NS. Western immunoblot analysis using H-NS and StpA antibodies showed decreased amounts of H-NS protein in NLM2173, and this reduction in H-NS correlated with an increase of StpA protein. Northern blot analysis with a dsbA-specific probe showed an increase in dsbA transcript during exponential phase of growth. Direct binding of H-NS to the dsbA promoter region was verified using purified H-NS in electrophoretic mobility shift assays. Thus, a reduction in H-NS protein is correlated with a derepression of dsbA in NLM2173, suggesting that H-NS normally plays a role in suppressing the expression of dsbA during exponential phase growth.

scholarly journals SlyA and HilD Counteract H-NS-Mediated Repression on the ssrAB Virulence Operon of Salmonella enterica Serovar Typhimurium and Thus Promote Its Activation by OmpR

2019 ◽  
Vol 201 (8) ◽  
Author(s):  
María M. Banda ◽  
Crispín Zavala-Alvarado ◽  
Deyanira Pérez-Morales ◽  
Víctor H. Bustamante
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Growth Conditions ◽  
The Other ◽  
Regulatory Mechanisms ◽  
Two Component System ◽  
Content Type ◽  
Additive Action ◽  
Serovar Typhimurium ◽  
Bacterial Fitness

ABSTRACT H-NS-mediated repression of acquired genes and the subsequent adaptation of regulatory mechanisms that counteract this repression have played a central role in the Salmonella pathogenicity evolution. The Salmonella pathogenicity island 2 (SPI-2) is an acquired chromosomal region containing genes necessary for Salmonella enterica to colonize and replicate in different niches of hosts. The ssrAB operon, located in SPI-2, encodes the two-component system SsrA-SsrB, which positively controls the expression of the SPI-2 genes but also other many genes located outside SPI-2. Several regulators have been involved in the expression of ssrAB, such as the ancestral regulators SlyA and OmpR, and the acquired regulator HilD. In this study, we show how SlyA, HilD, and OmpR coordinate to induce the expression of ssrAB under different growth conditions. We found that when Salmonella enterica serovar Typhimurium is grown in nutrient-rich lysogeny broth (LB), SlyA and HilD additively counteract H-NS-mediated repression on ssrAB, whereas in N-minimal medium (N-MM), SlyA antagonizes H-NS-mediated repression on ssrAB independently of HilD. Interestingly, our results indicate that OmpR is required for the expression of ssrAB independently of the growth conditions, even in the absence of repression by H-NS. Therefore, our data support two mechanisms adapted for the expression of ssrAB under different growth conditions. One involves the additive action of SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on ssrAB, thus favoring in both cases the activation of ssrAB by OmpR. IMPORTANCE The global regulator H-NS represses the expression of acquired genes and thus avoids possible detrimental effects on bacterial fitness. Regulatory mechanisms are adapted to induce expression of the acquired genes in particular niches to obtain a benefit from the information encoded in the foreign DNA, as for pathogenesis. Here, we show two mechanisms that were integrated for the expression of virulence genes in Salmonella Typhimurium. One involves the additive action of the regulators SlyA and HilD, whereas the other involves SlyA, but not HilD, to counteract H-NS-mediated repression on the ssrAB operon, thus favoring its activation by the OmpR regulator. To our knowledge, this is the first report involving the coordinated action of two regulators to counteract H-NS-mediated repression.

scholarly journals Polynucleotide Phosphorylase Negatively Controls spv Virulence Gene Expression in Salmonella enterica

2006 ◽  
Vol 74 (2) ◽  
pp. 1243-1254 ◽  
Author(s):  
Sofia Eriksson Ygberg ◽  
Mark O. Clements ◽  
Anne Rytkönen ◽  
Arthur Thompson ◽  
David W. Holden ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Cold Shock ◽  
Virulence Gene ◽  
Growth Conditions ◽  
Polynucleotide Phosphorylase ◽  
Virulence Gene Expression ◽  
Cold Shock Response ◽  
Serovar Typhimurium ◽  
Whole Genome Microarray

ABSTRACT Mutational inactivation of the cold-shock-associated exoribonuclease polynucleotide phosphorylase (PNPase; encoded by the pnp gene) in Salmonella enterica serovar Typhimurium was previously shown to enable the bacteria to cause chronic infection and to affect the bacterial replication in BALB/c mice (M. O. Clements et al., Proc. Natl. Acad. Sci. USA 99:8784-8789, 2002). Here, we report that PNPase deficiency results in increased expression of Salmonella plasmid virulence (spv) genes under in vitro growth conditions that allow induction of spv expression. Furthermore, whole-genome microarray-based transcriptome analyses of bacteria growing inside murine macrophage-like J774.A.1 cells revealed six genes as being significantly up-regulated in the PNPase-deficient background, which included spvABC, rtcB, entC, and STM2236. Mutational inactivation of the spvR regulator diminished the increased expression of spv observed in the pnp mutant background, implying that PNPase acts upstream of or at the level of SpvR. Finally, competition experiments revealed that the growth advantage of the pnp mutant in BALB/c mice was dependent on spvR as well. Combined, our results support the idea that in S. enterica PNPase, apart from being a regulator of the cold shock response, also functions in tuning the expression of virulence genes and bacterial fitness during infection.

scholarly journals Salmonella enterica Serovar Typhimurium rdoA Is Growth Phase Regulated and Involved in Relaying Cpx-Induced Signals

2003 ◽  
Vol 185 (2) ◽  
pp. 432-443 ◽  
Author(s):  
P. Suntharalingam ◽  
H. Spencer ◽  
C. V. Gallant ◽  
N. L. Martin
Keyword(s):  
Stress Response ◽  
Growth Phase ◽  
Salmonella Enterica ◽  
Phase Variation ◽  
Maximal Activity ◽  
Coding Region ◽  
Upstream Gene ◽  
Stress Response Pathway ◽  
Serovar Typhimurium ◽  
Null Strain

ABSTRACT The disulfide oxidoreductase, DsbA, mediates disulfide bond formation in proteins as they enter or pass through the periplasm of gram-negative bacteria. Although DsbA function has been well characterized, less is known about the factors that control its expression. Previous studies with Escherichia coli demonstrated that dsbA is part of a two-gene operon that includes an uncharacterized, upstream gene, yihE, that is positively regulated via the Cpx stress response pathway. To clarify the role of the yihE homologue on dsbA expression in Salmonella enterica serovar Typhimurium, the effect of this gene (termed rdoA) on the regulation of dsbA expression was investigated. Transcriptional assays assessing rdoA promoter activity showed growth phase-dependent expression with maximal activity in stationary phase. Significant quantities of rdoA and dsbA transcripts exist in serovar Typhimurium, but only extremely low levels of rdoA-dsbA cotranscript were detected. Activation of the Cpx system in serovar Typhimurium increased synthesis of both rdoA- and dsbA-specific transcripts but did not significantly alter the levels of detectable cotranscript. These results indicate that Cpx-mediated induction of dsbA transcription in serovar Typhimurium does not occur through an rdoA-dsbA cotranscript. A deletion of the rdoA coding region was constructed to definitively test the relevance of the rdoA-dsbA cotranscript to dsbA expression. The absence of RdoA affects DsbA expression levels when the Cpx system is activated, and providing rdoA in trans complements this phenotype, supporting the hypothesis that a bicistronic mechanism is not involved in serovar Typhimurium dsbA regulation. The rdoA null strain was also shown to be altered in flagellar phase variation. First it was found that induction of the Cpx stress response pathway switched flagellar synthesis to primarily phase 2 flagellin, and this effect was then found to be abrogated in the rdoA null strain, suggesting the involvement of RdoA in mediating Cpx-related signaling.

scholarly journals A Nutrient-Tunable Bistable Switch Controls Motility in Salmonella enterica Serovar Typhimurium

mBio ◽  
2014 ◽  
Vol 5 (5) ◽  
Author(s):  
Santosh Koirala ◽  
Patrick Mears ◽  
Martin Sim ◽  
Ido Golding ◽  
Yann R. Chemla ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Phenotypic Diversity ◽  
Complex Mixture ◽  
Growth Conditions ◽  
General Mechanism ◽  
Bistable Switch ◽  
Content Type ◽  
Motile Cells ◽  
Serovar Typhimurium

ABSTRACTMany bacteria are motile only when nutrients are scarce. In contrast,Salmonella entericaserovar Typhimurium is motile only when nutrients are plentiful, suggesting that this bacterium uses motility for purposes other than foraging, most likely for host colonization. In this study, we investigated how nutrients affect motility inS. entericaand found that they tune the fraction of motile cells. In particular, we observed coexisting populations of motile and nonmotile cells, with the distribution being determined by the concentration of nutrients in the growth medium. Interestingly,S. entericaresponds not to a single nutrient but apparently to a complex mixture of them. Using a combination of experimentation and mathematical modeling, we investigated the mechanism governing this behavior and found that it results from two antagonizing regulatory proteins, FliZ and YdiV. We also found that a positive feedback loop involving the alternate sigma factor FliA is required, although its role appears solely to amplify FliZ expression. We further demonstrate that the response is bistable: that is, genetically identical cells can exhibit different phenotypes under identical growth conditions. Together, these results uncover a new facet of the regulation of the flagellar genes inS. entericaand further demonstrate how bacteria employ phenotypic diversity as a general mechanism for adapting to change in their environment.IMPORTANCEMany bacteria employ flagella for motility. These bacteria are often not constitutively motile but become so only in response to specific environmental cues. The most common is nutrient starvation. Interestingly, inSalmonella entericaserovar Typhimurium, nutrients enhance the expression of flagella, suggesting that motility is used for purposes other than foraging. In this work, we investigated how nutrients affect motility inS. entericaand found that nutrients tune the fraction of motile cells within a population. Using both experimental and mathematical analysis, we determined the mechanism governing this tunable response. We further demonstrated that the response is bistable: that is, genetically identical cells can exhibit different phenotypes under identical growth conditions. These results reveal a new facet of motility inS. entericaand demonstrate that nutrients determine not only where these bacteria swim but also the fraction of them that do so.

scholarly journals Uptake and Replication of Salmonella enterica in Acanthamoeba rhysodes

2004 ◽  
Vol 70 (6) ◽  
pp. 3706-3714 ◽  
Author(s):  
Dilek Tezcan-Merdol ◽  
Marianne Ljungstr�m ◽  
Jadwiga Winiecka-Krusnell ◽  
Ewert Linder ◽  
Lars Engstrand ◽  
...  
Keyword(s):  
Bacterial Growth ◽  
Salmonella Enterica ◽  
Morphological Changes ◽  
Pathogenicity Island ◽  
Growth Conditions ◽  
Intracellular Bacteria ◽  
Virulence Plasmid ◽  
Cytotoxic Effects ◽  
Prolonged Incubation ◽  
Serovar Typhimurium

ABSTRACT The ability of salmonellae to become internalized and to survive and replicate in amoebae was evaluated by using three separate serovars of Salmonella enterica and five different isolates of axenic Acanthamoeba spp. In gentamicin protection assays, Salmonella enterica serovar Dublin was internalized more efficiently than Salmonella enterica serovar Enteritidis or Salmonella enterica serovar Typhimurium in all of the amoeba isolates tested. The bacteria appeared to be most efficiently internalized by Acanthamoeba rhysodes. Variations in bacterial growth conditions affected internalization efficiency, but this effect was not altered by inactivation of hilA, a key regulator in the expression of the invasion-associated Salmonella pathogenicity island 1. Microscopy of infected A. rhysodes revealed that S. enterica resided within vacuoles. Prolonged incubation resulted in a loss of intracellular bacteria associated with morphological changes and loss of amoebae. In part, these alterations were associated with hilA and the Salmonella virulence plasmid. The data show that Acanthamoeba spp. can differentiate between different serovars of salmonellae and that internalization is associated with cytotoxic effects mediated by defined Salmonella virulence loci.

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