scholarly journals The Majority of Typhoid Toxin-Positive Salmonella Serovars Encode ArtB, an Alternate Binding Subunit

mSphere ◽  
2021 ◽  
Vol 6 (1) ◽  
Author(s):  
A. Gaballa ◽  
R. A. Cheng ◽  
A. S. Harrand ◽  
A. R. Cohn ◽  
M. Wiedmann
Keyword(s):  
Virulence Factors ◽  
Salmonella Enterica ◽  
Affinity Purification ◽  
Growth Conditions ◽  
Minor Role ◽  
Content Type ◽  
Toxin Binding ◽  
Typhoid Toxin ◽  
Binding Subunit

ABSTRACT Salmonella enterica encodes a wide array of virulence factors. One novel virulence factor, an A2B5 toxin known as the typhoid toxin (TT), was recently identified among a variety of S. enterica serovars. While past studies have shown that some serovars encode both the TT (active subunits CdtB and PltA and binding subunit PltB) and a second binding subunit (ArtB), these serovars were thought to be the exception. Here, we show that genes encoding the TT are detected in more than 100 serovars representing distinct phylogenetic lineages of S. enterica subsp. enterica, although clade B and section Typhi are significantly more likely to encode TT genes than serovars from other clades. Furthermore, we show that 81% of these TT-positive serovars also encode artB, suggesting that the cooccurrence of both toxin binding subunits is considerably more common than previously thought. A combination of in silico modeling, bacterial two-hybrid system screening, and tandem affinity purification (TAP) of toxin subunits suggests that ArtB and PltB interact in vitro, at least under some growth conditions. While different growth conditions yielded slightly higher transcript abundances of artB and pltB, both genes had their highest relative transcript abundances when Salmonella was grown under low-Mg2+ conditions, suggesting that ArtB and PltB may compete for inclusion in the TT. Together, our results suggest that ArtB likely plays an important and previously underappreciated role in the biology of the TT produced by typhoidal and nontyphoidal Salmonella. IMPORTANCE While previous reports had suggested that the typhoid toxin (TT) could potentially use ArtB as an alternate binding subunit, this was thought to play a minor role in the evolution and biology of the toxin. In this study, we establish that both TT genes and artB are widespread among Salmonella enterica subsp. enterica, suggesting that TT likely plays a broader role in Salmonella virulence that extends beyond its proposed role in typhoid fever. Furthermore, our data suggest the selective maintenance of both toxin binding subunits, which may compete for inclusion in the holotoxin. Last, our data support the importance of characterizing diverse nontyphoidal Salmonella (NTS) serovars, as the presence of classically defined typhoidal virulence factors among NTS serovars continues to challenge the typhoid-nontyphoid Salmonella paradigm.

scholarly journals The Typhoid Toxin Produced by the NontyphoidalSalmonella entericaSerotype Javiana Is Required for Induction of a DNA Damage ResponseIn Vitroand Systemic SpreadIn Vivo

mBio ◽  
2018 ◽  
Vol 9 (2) ◽  
Author(s):  
Rachel A. Miller ◽  
Michael I. Betteken ◽  
Xiaodong Guo ◽  
Craig Altier ◽  
Gerald E. Duhamel ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Death ◽  
Salmonella Enterica ◽  
Biologically Active ◽  
Genes Encoding ◽  
Typhoid Toxin ◽  
Binding Subunit

ABSTRACTTheSalmonellacytolethal distending toxin (S-CDT), first described as the “typhoid toxin” inSalmonella entericasubsp.entericaserotype Typhi, induces DNA damage in eukaryotic cells. Recent studies have shown that more than 40 nontyphoidalSalmonella(NTS) serotypes carry genes that encode S-CDT, yet very little is known about the activity, function, and role of S-CDT in NTS. Here we show that deletion of genes encoding the binding subunit (pltB) and a bacteriophage muramidase predicted to play a role in toxin export (ttsA) does not abolish toxin activity in the S-CDT-positive NTSSalmonella entericasubsp.entericaserotype Javiana. However,S.Javiana strains harboring deletions of bothpltBand its homologartB, had a complete loss of S-CDT activity, suggesting thatS.Javiana carries genes encoding two variants of the binding subunit. S-CDT-mediated DNA damage, as determined by phosphorylation of histone 2AX (H2AX), producing phosphorylated H2AX (γH2AX), was restricted to epithelial cells in S and G2/M phases of the cell cycle and did not result in apoptosis or cell death. Compared to mice infected with a ΔcdtBstrain, mice infected with wild-typeS.Javiana had significantly higher levels ofS.Javiana in the liver, but not in the spleen, ileum, or cecum. Overall, we show that production of active S-CDT by NTS serotypeS.Javiana requires different genes (cdtB,pltA, and eitherpltBorartB) for expression of biologically active toxin than those reported for S-CDT production byS.Typhi (cdtB,pltA,pltB, andttsA). However, as inS.Typhi, NTS S-CDT influences the outcome of infection bothin vitroandin vivo.IMPORTANCENontyphoidalSalmonella(NTS) are a major cause of bacterial food-borne illness worldwide; however, our understanding of virulence mechanisms that determine the outcome and severity of nontyphoidal salmonellosis is incompletely understood. Here we show that S-CDT produced by NTS plays a significant role in the outcome of infection bothin vitroandin vivo, highlighting S-CDT as an important virulence factor for nontyphoidalSalmonellaserotypes. Our data also contribute novel information about the function of S-CDT, as S-CDT-mediated DNA damage occurs only during certain phases of the cell cycle, and the resulting damage does not induce cell death as assessed using a propidium iodide exclusion assay. Importantly, our data support that, despite having genetically similar S-CDT operons, NTS serotypeS.Javiana has different genetic requirements thanS.Typhi, for the production and export of active S-CDT.

scholarly journals Expression of Virulence Factors by Staphylococcus aureus Grown in Serum

2011 ◽  
Vol 77 (22) ◽  
pp. 8097-8105 ◽  
Author(s):  
Yuichi Oogai ◽  
Miki Matsuo ◽  
Masahito Hashimoto ◽  
Fuminori Kato ◽  
Motoyuki Sugai ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Virulence Factors ◽  
Iron Acquisition ◽  
Calf Serum ◽  
Growth Conditions ◽  
Defined Medium ◽  
Chemically Defined Medium ◽  
Regulatory Factor ◽  
Content Type

ABSTRACTStaphylococcus aureusproduces many virulence factors, including toxins, immune-modulatory factors, and exoenzymes. Previous studies involving the analysis of virulence expression were mainly performed byin vitroexperiments using bacterial medium. However, whenS. aureusinfects a host, the bacterial growth conditions are quite different from those in a medium, which may be related to the different expression of virulence factors in the host. In this study, we investigated the expression of virulence factors inS. aureusgrown in calf serum. The expression of many virulence factors, including hemolysins, enterotoxins, proteases, and iron acquisition factors, was significantly increased compared with that in bacterial medium. In addition, the expression of RNA III, a global regulon for virulence expression, was significantly increased. This effect was partially restored by the addition of 300 μM FeCl3into serum, suggesting that iron depletion is associated with the increased expression of virulence factors in serum. In chemically defined medium without iron, a similar effect was observed. In a mutant withagrinactivated grown in serum, the expression of RNA III,psm, andsec4was not increased, while other factors were still induced in the mutant, suggesting that another regulatory factor(s) is involved. In addition, we found that serum albumin is a major factor for the capture of free iron to prevent the supply of iron to bacteria grown in serum. These results indicate thatS. aureusexpresses virulence factors in adaptation to the host environment.

scholarly journals Genome Scanning for Conditionally Essential Genes in Salmonella enterica Serotype Typhimurium

2012 ◽  
Vol 78 (9) ◽  
pp. 3098-3107 ◽  
Author(s):  
Anita Khatiwara ◽  
Tieshan Jiang ◽  
Sam-Sun Sung ◽  
Turki Dawoud ◽  
Jeong Nam Kim ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Bacterial Species ◽  
Growth Conditions ◽  
Luria Bertani ◽  
Mutant Library ◽  
Content Type ◽  
A Genome ◽  
Gene Functions ◽  
New Gene

ABSTRACTAs more whole-genome sequences become available, there is an increasing demand for high-throughput methods that link genes to phenotypes, facilitating discovery of new gene functions. In this study, we describe a new version of the Tn-seq method involving a modified EZ:Tn5transposon for genome-wide and quantitative mapping of all insertions in a complex mutant library utilizing massively parallel Illumina sequencing. This Tn-seq method was applied to a genome-saturatingSalmonella entericaserotype Typhimurium mutant library recovered from selection under 3 differentin vitrogrowth conditions (diluted Luria-Bertani [LB] medium, LB medium plus bile acid, and LB medium at 42°C), mimicking some aspects of host stressors. We identified an overlapping set of 105 protein-coding genes inS. Typhimurium that are conditionally essential under at least one of the above selective conditions. Competition assays using 4 deletion mutants (pyrD,glnL,recD, and STM14_5307) confirmed the phenotypes predicted by Tn-seq data, validating the utility of this approach in discovering new gene functions. With continuously increasing sequencing capacity of next generation sequencing technologies, this robust Tn-seq method will aid in revealing unexplored genetic determinants and the underlying mechanisms of various biological processes inSalmonellaand the other approximately 70 bacterial species for which EZ:Tn5mutagenesis has been established.

scholarly journals A Rhodobacter sphaeroides Protein Mechanistically Similar to Escherichia coli DksA Regulates Photosynthetic Growth

mBio ◽  
2014 ◽  
Vol 5 (3) ◽  
Author(s):  
Christopher W. Lennon ◽  
Kimberly C. Lemmer ◽  
Jessica L. Irons ◽  
Max I. Sellman ◽  
Timothy J. Donohue ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Structure Function ◽  
Rhodobacter Sphaeroides ◽  
Fatty Acid Content ◽  
Regulatory Protein ◽  
Growth Conditions ◽  
Globular Domain ◽  
Content Type ◽  
E Coli

ABSTRACTDksA is a global regulatory protein that, together with the alarmone ppGpp, is required for the “stringent response” to nutrient starvation in the gammaproteobacteriumEscherichia coliand for more moderate shifts between growth conditions. DksA modulates the expression of hundreds of genes, directly or indirectly. Mutants lacking a DksA homolog exhibit pleiotropic phenotypes in other gammaproteobacteria as well. Here we analyzed the DksA homolog RSP2654 in the more distantly relatedRhodobacter sphaeroides, an alphaproteobacterium. RSP2654 is 42% identical and similar in length toE. coliDksA but lacks the Zn finger motif of theE. coliDksA globular domain. Deletion of the RSP2654 gene results in defects in photosynthetic growth, impaired utilization of amino acids, and an increase in fatty acid content. RSP2654 complements the growth and regulatory defects of anE. colistrain lacking thedksAgene and modulates transcriptionin vitrowithE. coliRNA polymerase (RNAP) similarly toE. coliDksA. RSP2654 reduces RNAP-promoter complex stabilityin vitrowith RNAPs fromE. coliorR. sphaeroides, alone and synergistically with ppGpp, suggesting that even though it has limited sequence identity toE. coliDksA (DksAEc), it functions in a mechanistically similar manner. We therefore designate the RSP2654 protein DksARsp. Our work suggests that DksARsphas distinct and important physiological roles in alphaproteobacteria and will be useful for understanding structure-function relationships in DksA and the mechanism of synergy between DksA and ppGpp.IMPORTANCEThe role of DksA has been analyzed primarily in the gammaproteobacteria, in which it is best understood for its role in control of the synthesis of the translation apparatus and amino acid biosynthesis. Our work suggests that DksA plays distinct and important physiological roles in alphaproteobacteria, including the control of photosynthesis inRhodobacter sphaeroides. The study of DksARsp, should be useful for understanding structure-function relationships in the protein, including those that play a role in the little-understood synergy between DksA and ppGpp.

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 Low-Molecular-Weight Metabolites Secreted by Paenibacillus larvae as Potential Virulence Factors of American Foulbrood

2014 ◽  
Vol 80 (8) ◽  
pp. 2484-2492 ◽  
Author(s):  
Hedwig-Annabell Schild ◽  
Sebastian W. Fuchs ◽  
Helge B. Bode ◽  
Bernd Grünewald
Keyword(s):  
Molecular Weight ◽  
Virulence Factors ◽  
Gene Clusters ◽  
Paenibacillus Larvae ◽  
Economic Losses ◽  
Low Molecular Weight ◽  
American Foulbrood ◽  
Toxic Activity ◽  
Content Type

ABSTRACTThe spore-forming bacteriumPaenibacillus larvaecauses a severe and highly infective bee disease, American foulbrood (AFB). Despite the large economic losses induced by AFB, the virulence factors produced byP. larvaeare as yet unknown. To identify such virulence factors, we experimentally infected young, susceptible larvae of the honeybee,Apis mellifera carnica, with differentP. larvaeisolates. Honeybee larvae were rearedin vitroin 24-well plates in the laboratory after isolation from the brood comb. We identified genotype-specific differences in the etiopathology of AFB between the tested isolates ofP. larvae, which were revealed by differences in the median lethal times. Furthermore, we confirmed that extracts ofP. larvaecultures contain low-molecular-weight compounds, which are toxic to honeybee larvae. Our data indicate thatP. larvaesecretes metabolites into the medium with a potent honeybee toxic activity pointing to a novel pathogenic factor(s) ofP. larvae. Genome mining ofP. larvaesubsp.larvaeBRL-230010 led to the identification of several biosynthesis gene clusters putatively involved in natural product biosynthesis, highlighting the potential ofP. larvaeto produce such compounds.

scholarly journals Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and ReducesIn VivoPathogenicity

2012 ◽  
Vol 57 (1) ◽  
pp. 445-451 ◽  
Author(s):  
Ilka Tiemy Kato ◽  
Renato Araujo Prates ◽  
Caetano Padial Sabino ◽  
Beth Burgwyn Fuchs ◽  
George P. Tegos ◽  
...  
Keyword(s):  
Candida Albicans ◽  
Virulence Factors ◽  
Sodium Dodecyl ◽  
Systemic Infection ◽  
Tube Formation ◽  
Photodynamic Inactivation ◽  
Content Type ◽  
Daughter Cells

ABSTRACTThe objective of this study was to evaluate whetherCandida albicansexhibits altered pathogenicity characteristics following sublethal antimicrobial photodynamic inactivation (APDI) and if such alterations are maintained in the daughter cells.C. albicanswas exposed to sublethal APDI by using methylene blue (MB) as a photosensitizer (0.05 mM) combined with a GaAlAs diode laser (λ 660 nm, 75 mW/cm2, 9 to 27 J/cm2).In vitro, we evaluated APDI effects onC. albicansgrowth, germ tube formation, sensitivity to oxidative and osmotic stress, cell wall integrity, and fluconazole susceptibility.In vivo, we evaluatedC. albicanspathogenicity with a mouse model of systemic infection. Animal survival was evaluated daily. Sublethal MB-mediated APDI reduced the growth rate and the ability ofC. albicansto form germ tubes compared to untreated cells (P< 0.05). Survival of mice systemically infected withC. albicanspretreated with APDI was significantly increased compared to mice infected with untreated yeast (P< 0.05). APDI increasedC. albicanssensitivity to sodium dodecyl sulfate, caffeine, and hydrogen peroxide. The MIC for fluconazole forC. albicanswas also reduced following sublethal MB-mediated APDI. However, none of those pathogenic parameters was altered in daughter cells ofC. albicanssubmitted to APDI. These data suggest that APDI may inhibit virulence factors and reducein vivopathogenicity ofC. albicans. The absence of alterations in daughter cells indicates that APDI effects are transitory. The MIC reduction for fluconazole following APDI suggests that this antifungal could be combined with APDI to treatC. albicansinfections.

scholarly journals A Salmonella Virulence Factor Activates the NOD1/NOD2 Signaling Pathway

mBio ◽  
2011 ◽  
Vol 2 (6) ◽  
Author(s):  
A. Marijke Keestra ◽  
Maria G. Winter ◽  
Daisy Klein-Douwel ◽  
Mariana N. Xavier ◽  
Sebastian E. Winter ◽  
...  
Keyword(s):  
Signaling Pathway ◽  
Type Iii Secretion ◽  
Salmonella Enterica ◽  
Intestinal Inflammation ◽  
Inflammatory Responses ◽  
Type Iii Secretion System ◽  
Secretion System ◽  
Content Type ◽  
Type Iii

ABSTRACTThe invasion-associated type III secretion system (T3SS-1) ofSalmonella entericaserotype Typhimurium (S. Typhimurium) activates the transcription factor NF-κB in tissue culture cells and induces inflammatory responses in animal models through unknown mechanisms. Here we show that bacterial delivery or ectopic expression of SipA, a T3SS-1-translocated protein, led to the activation of the NOD1/NOD2 signaling pathway and consequent RIP2-mediated induction of NF-κB-dependent inflammatory responses. SipA-mediated activation of NOD1/NOD2 signaling was independent of bacterial invasionin vitrobut required an intact T3SS-1. In the mouse colitis model, SipA triggered mucosal inflammation in wild-type mice but not in NOD1/NOD2-deficient mice. These findings implicate SipA-driven activation of the NOD1/NOD2 signaling pathway as a mechanism by which the T3SS-1 induces inflammatory responsesin vitroandin vivo.IMPORTANCESalmonella entericaserotype Typhimurium (S. Typhimurium) deploys a type III secretion system (T3SS-1) to induce intestinal inflammation and benefits from the ensuing host response, which enhances growth of the pathogen in the intestinal lumen. However, the mechanisms by which the T3SS-1 triggers inflammatory responses have not been resolved. Here we show that the T3SS-1 effector protein SipA induces NF-κB activation and intestinal inflammation by activating the NOD1/NOD2 signaling pathway. These data suggest that the T3SS-1 escalates innate responses through a SipA-mediated activation of pattern recognition receptors in the host cell cytosol.

scholarly journals Complete Genome Sequence of Lactococcus lactis subsp. lactis Strain 14B4, Which Inhibits the Growth of Salmonella enterica Serotype Poona In Vitro

2018 ◽  
Vol 7 (19) ◽  
Author(s):  
Thao D. Tran ◽  
Steven Huynh ◽  
Craig T. Parker ◽  
Ruyang Han ◽  
Robert Hnasko ◽  
...  
Keyword(s):  
Lactococcus Lactis ◽  
Genome Sequence ◽  
Complete Genome Sequence ◽  
Salmonella Enterica ◽  
Complete Genome ◽  
Northern California ◽  
Content Type ◽  
Lactococcus Lactis Subsp ◽  
Lactis Strain

We present here the complete genome sequence of Lactococcus lactis strain 14B4, isolated from almond drupes in northern California. This strain was observed to inhibit the growth of Salmonella enterica serotype Poona strain RM3363 in vitro.

scholarly journals Efficacy of Biocides Used in the Modern Food Industry To Control Salmonella enterica, and Links between Biocide Tolerance and Resistance to Clinically Relevant Antimicrobial Compounds

2012 ◽  
Vol 78 (9) ◽  
pp. 3087-3097 ◽  
Author(s):  
Orla Condell ◽  
Carol Iversen ◽  
Shane Cooney ◽  
Karen A. Power ◽  
Ciara Walsh ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Food Industry ◽  
Multidrug Resistant ◽  
Cross Resistance ◽  
Antimicrobial Compounds ◽  
Cross Tolerance ◽  
Content Type ◽  
Food Grade ◽  
High Level

ABSTRACTBiocides play an essential role in limiting the spread of infectious disease. The food industry is dependent on these agents, and their increasing use is a matter for concern. Specifically, the emergence of bacteria demonstrating increased tolerance to biocides, coupled with the potential for the development of a phenotype of cross-resistance to clinically important antimicrobial compounds, needs to be assessed. In this study, we investigated the tolerance of a collection of susceptible and multidrug-resistant (MDR)Salmonella entericastrains to a panel of seven commercially available food-grade biocide formulations. We explored their abilities to adapt to these formulations and their active biocidal agents, i.e., triclosan, chlorhexidine, hydrogen peroxide, and benzalkonium chloride, after sequential rounds ofin vitroselection. Finally, cross-tolerance of different categories of biocidal formulations, their active agents, and the potential for coselection of resistance to clinically important antibiotics were investigated. Six of seven food-grade biocide formulations were bactericidal at their recommended working concentrations. All showed a reduced activity against both surface-dried and biofilm cultures. A stable phenotype of tolerance to biocide formulations could not be selected. Upon exposure ofSalmonellastrains to an active biocidal compound, a high-level of tolerance was selected for a number ofSalmonellaserotypes. No cross-tolerance to the different biocidal agents or food-grade biocide formulations was observed. Most tolerant isolates displayed changes in their patterns of susceptibility to antimicrobial compounds. Food industry biocides are effective against planktonicSalmonella. When exposed to sublethal concentrations of individual active biocidal agents, tolerant isolates may emerge. This emergence was associated with changes in antimicrobial susceptibilities.

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