scholarly journals Identification and Testing of Porphyromonas gingivalis Virulence Genes with a pPGIVET System

2002 ◽  
Vol 70 (2) ◽  
pp. 928-937 ◽  
Author(s):  
Yi Wu ◽  
Seok-Woo Lee ◽  
Jeffrey D. Hillman ◽  
Ann Progulske-Fox
Keyword(s):  
Mutant Strain ◽  
Porphyromonas Gingivalis ◽  
Type Strain ◽  
Virulence Genes ◽  
Wild Type Strain ◽  
Receptor Protein ◽  
Wild Type ◽  
Kb Cells ◽  
Mutant Strains

ABSTRACT An in vivo expression technology (IVET) system was designed to identify previously unknown virulence genes of Porphyromonas gingivalis. Fourteen ivi (for in vivo induced) genes that are induced during infection in a mouse abscess model were identified in our study. Of these, seven had homology to genes in the NCBI database, and the rest had no homology to reported DNA sequences. In order to determine virulence-related properties of these genes, three mutant strains, deleted of ivi8 (no homology to genes in the database), ivi10 (homologous to a putative TonB-dependent outer membrane receptor protein), and ivi11 (an immunoreactive 33-kDa antigen PG125 in P. gingivalis), were created. The mutants were tested in a mouse abscess model for alterations in virulence relative to the wild type by a competition assay in BALB/c mice. After 5 days we observed the enrichment of the wild-type strain over mutant strains Δivi10 and Δivi11, which indicated that mutant strains Δivi10 and Δivi11 are less able to survive in this model than the wild-type strain, while Δivi8 survives as well as the wild-type strain. We propose that knockout of these ivi genes reduced the ability of the mutated P. gingivalis to survive and cause infection compared to the wild-type strain at the site of injection. Also, in separate experiments, groups of mice were challenged with subcutaneous injections of each individual mutant strain (Δivi8, Δivi10, and Δivi11) or with the wild-type strain alone and were then examined to assess their general health status. The results showed that knockout of these ivi genes conferred a reduction in virulence. The ability of the mutants to invade KB cells compared to the wild type was also determined. Interestingly, the CFU counts of the mutant strain Δivi10 recovered from KB cells were eight times lower than those of the wild type, indicating that this mutant has a lower capacity for invasion. These results demonstrate that IVET is a powerful tool in discovering virulence genes and the significant role that ivi genes play in the pathogenesis of this species.

scholarly journals Regulation of ppk Expression and In Vivo Function of Ppk in Streptomyces lividans TK24

2006 ◽  
Vol 188 (17) ◽  
pp. 6269-6276 ◽  
Author(s):  
Sofiane Ghorbel ◽  
Aleksey Smirnov ◽  
Hichem Chouayekh ◽  
Brice Sperandio ◽  
Catherine Esnault ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Sufficient Conditions ◽  
Streptomyces Lividans ◽  
Antibiotic Biosynthesis ◽  
Wild Type ◽  
In The Wild

ABSTRACT The ppk gene of Streptomyces lividans encodes an enzyme catalyzing, in vitro, the reversible polymerization of the γ phosphate of ATP into polyphosphate and was previously shown to play a negative role in the control of antibiotic biosynthesis (H. Chouayekh and M. J. Virolle, Mol. Microbiol. 43:919-930, 2002). In the present work, some regulatory features of the expression of ppk were established and the polyphosphate content of S. lividans TK24 and the ppk mutant was determined. In Pi sufficiency, the expression of ppk was shown to be low but detectable. DNA gel shift experiments suggested that ppk expression might be controlled by a repressor using ATP as a corepressor. Under these conditions, short acid-soluble polyphosphates accumulated upon entry into the stationary phase in the wild-type strain but not in the ppk mutant strain. The expression of ppk under Pi-limiting conditions was shown to be much higher than that under Pi-sufficient conditions and was under positive control of the two-component system PhoR/PhoP. Under these conditions, the polyphosphate content of the cell was low and polyphosphates were reproducibly found to be longer and more abundant in the ppk mutant strain than in the wild-type strain, suggesting that Ppk might act as a nucleoside diphosphate kinase. In light of our results, a novel view of the role of this enzyme in the regulation of antibiotic biosynthesis in S. lividans TK24 is proposed.

scholarly journals A Single Amino Acid at Residue 188 of Hexon Protein is Responsible for the Pathogenicity of the Emerging Novel Fowl Adenovirus 4

2021 ◽  
Author(s):  
Yu Zhang ◽  
Aijing Liu ◽  
Yanan Wang ◽  
Hongyu Cui ◽  
Yulong Gao ◽  
...  
Keyword(s):  
Amino Acid ◽  
Mutant Strain ◽  
Molecular Basis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Live Attenuated Vaccine ◽  
Hexon Protein

Since 2015, severe hydropericardium-hepatitis syndrome (HHS) associated with a novel fowl adenovirus 4 (FAdV-4) has emerged in China, representing a new challenge for the poultry industry. Although various highly pathogenic FAdV-4 strains have been isolated, the virulence factor and the pathogenesis of novel FAdV-4 are unclear. In our previous studies, we reported that a large genomic deletion (1966 bp) is not related to increased virulence. In this study, two recombinant chimeric viruses, rHN20 strain and rFB2 strain, were generated from a highly pathogenic FAdV-4 strain by replacing hexon or fiber-2 gene of a non-pathogenic FAdV-4, respectively. Both chimeric strains showed similar titers to the wild type strain in vitro . Notably, rFB2 and the wild type strain induced 100% mortality, while no mortality or clinical signs appeared in chickens inoculated with rHN20, indicating that hexon, but not fiber-2, determines the novel FAdV-4 virulence. Furthermore, an R188I mutation in the hexon protein identified residue 188 as the key amino acid for the reduced pathogenicity. The rR188I mutant strain was significantly neutralized by chicken serum in vitro and in vivo , whereas the wild type strain was able to replicate efficiently. Finally, the immunogenicity of the rescued rR188I was investigated. Non-pathogenic rR188I provided full protection against lethal FAdV-4 challenge. Collectively, these findings provide an in-depth understanding of the molecular basis of novel FAdV-4 pathogenicity and present rR188I as a potential live attenuated vaccine candidate or a novel vaccine vector for HHS vaccines. Importance HHS associated with a novel FAdV-4 infection in chickens has caused huge economic losses to the poultry industry in China since 2015. The molecular basis for the increased virulence remains largely unknown. Here, we demonstrate that the hexon gene is vital for FAdV-4 pathogenicity. Furthermore, we show that the amino acid residue at position 188 of the hexon protein is responsible for pathogenicity. Importantly, the rR188I mutant strain was neutralized by chicken serum in vitro and in vivo , whereas the wild type strain was not. Further, the rR188I mutant strain provided complete protection against FAdV-4 challenge. Our results provide a molecular basis of the increased virulence of novel FAdV-4. We propose that the rR188I mutant is a potential live attenuated vaccine against HHS and a new vaccine vector for HHS-combined vaccines.

scholarly journals Impact of the Listeria monocytogenes Protein InlC on Infection in Mice

2013 ◽  
Vol 81 (4) ◽  
pp. 1334-1340 ◽  
Author(s):  
Nelly Leung ◽  
Antonella Gianfelice ◽  
Scott D. Gray-Owen ◽  
Keith Ireton
Keyword(s):  
Listeria Monocytogenes ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Bacterial Pathogen ◽  
Adaptor Protein ◽  
Single Amino Acid ◽  
Wild Type ◽  
Content Type

ABSTRACTThe bacterial pathogenListeria monocytogenescauses serious food-borne illnesses in pregnant women and the immunocompromised.L. monocytogenespromotes its internalization into host epithelial cells and then uses an F-actin-dependent motility process to spread from infected cells to surrounding healthy cells. In cultured enterocytes, efficient spread ofL. monocytogenesrequires the secreted bacterial protein InlC. InlC promotes dissemination by physically interacting with and antagonizing the function of the human adaptor protein Tuba. Here we examine the role of InlC and its interaction with host Tuba during infection in mice. The study took advantage of a single-amino-acid substitution (K173A) in InlC that impairs binding to human Tuba but does not affect InlC-mediated inhibition of the NF-κB pathway. Mice were inoculated intravenously with the wild-typeL. monocytogenesstrain EGD, an isogenic strain deleted for theinlCgene (ΔinlC), or a strain expressing K173A mutant InlC (inlC.K173A). The 50% lethal doses (LD50) for the ΔinlCorinlC.K173Amutant strain were approximately 4- or 6-fold greater than that for the wild-type strain, indicating a role forinlCin virulence. Compared to the wild-type strain, theinlC.K173Amutant strain exhibited lower bacterial loads in the liver. Histological analysis of livers indicated that the twoinlCmutant strains produced smaller foci of infection than did the wild-type strain. These smaller foci are consistent with a role for InlC in cell-to-cell spreadin vivo. Taken together, these results provide evidence that interaction of InlC with host Tuba is important for full virulence.

scholarly journals Identification of MglA-Regulated Genes Reveals Novel Virulence Factors in Francisella tularensis

2006 ◽  
Vol 74 (12) ◽  
pp. 6642-6655 ◽  
Author(s):  
Anna Brotcke ◽  
David S. Weiss ◽  
Charles C. Kim ◽  
Patrick Chain ◽  
Stephanie Malfatti ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Virulence Factors ◽  
Francisella Tularensis ◽  
Type Strain ◽  
Virulence Genes ◽  
Wild Type Strain ◽  
Transcriptional Profiling ◽  
Intracellular Bacterium ◽  
Wild Type

ABSTRACT The facultative intracellular bacterium Francisella tularensis causes the zoonotic disease tularemia. F. tularensis resides within host macrophages in vivo, and this ability is essential for pathogenesis. The transcription factor MglA is required for the expression of several Francisella genes that are necessary for replication in macrophages and for virulence in mice. We hypothesized that the identification of MglA-regulated genes in the Francisella genome by transcriptional profiling of wild-type and mglA mutant bacteria would lead to the discovery of new virulence factors utilized by F. tularensis. A total of 102 MglA-regulated genes were identified, the majority of which were positively regulated, including all of the Francisella pathogenicity island (FPI) genes. We mutated novel MglA-regulated genes and tested the mutants for their ability to replicate and induce cytotoxicity in macrophages and to grow in mice. Mutations in MglA-regulated genes within the FPI (pdpB and cds2) as well as outside the FPI (FTT0989, oppB, and FTT1209c) were either attenuated or hypervirulent in macrophages compared to the wild-type strain. All of these mutants exhibited decreased fitness in vivo in competition experiments with wild-type bacteria. We have identified five new Francisella virulence genes, and our results suggest that characterizations of additional MglA-regulated genes will yield further insights into the pathogenesis of this bacterium.

Evidence for plasmid-mediated chemotaxis ofPseudomonas putidatowards naphthalene and salicylate

1999 ◽  
Vol 46 (1) ◽  
pp. 1-6
Author(s):  
Sudip K Samanta ◽  
Rakesh K Jain
Keyword(s):  
Pseudomonas Putida ◽  
Mutant Strain ◽  
Recombinant Plasmid ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ecori Fragment ◽  
Wild Type ◽  
Mutant Strains ◽  
Degrading Microorganism

A naphthalene (Nap) and salicylate (Sal) degrading microorganism, Pseudomonas putida RKJ1, is chemotactic towards these compounds. This strain carries a 83 kb plasmid. A 25 kb EcoRI fragment of the plasmid contains the genes responsible for Nap degradation through Sal. RKJ5, the plasmid-cured derivative of RKJ1, is neither capable of degradation nor is chemotactic towards Nap or Sal. The recombinant plasmid pRKJ3, which contained a 25 kb EcoRI fragment, was transferred back into the plasmid-free wild-type strain RKJ5, and the transconjugant showed both degradation and chemotaxis. The recombinant plasmid pRKJ3 was also transferred into motile, plasmid-free P. putida KT2442. The resulting transconjugant (RKJ15) showed chemotaxis towards both Nap and Sal. Two mutant strains carrying deletions in pRKJ3 (in KT2442) with phenotypes Nap-Sal+and Nap-Sal-, were also tested for chemotaxis. It was found that the Nap-Sal+mutant strain showed chemotaxis towards Sal only, whereas the Nap-Sal-mutant strain is non-chemotactic towards both the compounds. These results suggest that the metabolism of Nap and Sal may be required for the chemotactic activity.Key words: Pseudomonas putida, plasmid-encoded chemotaxis, naphthalene, salicylate.

scholarly journals Heme Transport Contributes to In Vivo Fitness of Bordetella pertussis during Primary Infection in Mice

2006 ◽  
Vol 74 (3) ◽  
pp. 1741-1744 ◽  
Author(s):  
Timothy J. Brickman ◽  
Carin K. Vanderpool ◽  
Sandra K. Armstrong
Keyword(s):  
Bordetella Pertussis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Relative Fitness ◽  
Transport Systems ◽  
Receptor Protein ◽  
Wild Type ◽  
Iron Starvation ◽  
Virulence Attenuation

ABSTRACT Bordetella pertussis, the causative agent of whooping cough or pertussis, is an obligate human pathogen with multiple high-affinity iron transport systems. Maximal expression of the dedicated heme utilization functions encoded by the hurIR bhuRSTUV genes requires an iron starvation signal to relieve Fur repression at the hurIR promoter-operator and an inducing signal supplied by heme for HurI-mediated transcriptional activation at the bhuRSTUV promoter. The BhuR outer membrane receptor protein is required for heme uptake and for heme sensing for induction of bhuRSTUV transcription. It was hypothesized that heme utilization contributed to the success of B. pertussis as a pathogen. In this study, virulence attenuation resulting from inactivation of the B. pertussis heme system was assessed using mixed infection competition experiments in a mouse model. As a measure of in vivo fitness, the ability of a B. pertussis heme utilization mutant to colonize and persist was determined relative to that of an isogenic coinfecting wild-type strain. Relative fitness of the mutant strain declined significantly after 7 days postinfection and continued to decline throughout the remainder of the 28-day infection time course. In parallel infections using inocula supplemented with an inducing 2 μM concentration of hemin chloride, hemin coadministration augmented the competitive advantage of the wild-type strain over the mutant. The results confirm that heme utilization contributes to the pathogenesis of B. pertussis in the mouse infection model and indicate that heme utilization may be most important for adaptation to host conditions existing during the later stages of infection.

scholarly journals Lysine-specific gingipain K and heme/hemoglobin receptor HmuR are involved in heme utilization in Porphyromonas gingivalis.

2004 ◽  
Vol 51 (1) ◽  
pp. 253-262 ◽  
Author(s):  
Waltena Simpson ◽  
Teresa Olczak ◽  
Caroline A Genco
Keyword(s):  
Porphyromonas Gingivalis ◽  
Type Strain ◽  
Double Mutant ◽  
Wild Type Strain ◽  
Wild Type ◽  
Outer Membrane Receptor ◽  
Iron Source ◽  
Identification And Characterization

We have previously reported on the identification and characterization of the Porphyromonas gingivalis A7436 strain outer membrane receptor HmuR, which is involved in the acquisition of hemin and hemoglobin. We demonstrated that HmuR interacts with the lysine- (Kgp) and arginine- (HRgpA) specific proteases (gingipains) and that Kgp and HRgpA can bind and degrade hemoglobin. Here, we report on the physiological significance of the HmuR-Kgp complex in heme utilization in P. gingivalis through the construction and characterization of a defined kgp mutant and a hmuR kgp double mutant in P. gingivalis A7436. The P. gingivalis kgp mutant exhibited a decreased ability to bind both hemin and hemoglobin. Growth of this strain with hemoglobin was delayed and its ability to utilize hemin as a sole iron source was diminished as compared to the wild type strain. Inactivation of both the hmuR and kgp genes resulted in further decreased ability of P. gingivalis to bind hemoglobin and hemin, as well as diminished ability to utilize either hemin or hemoglobin as a sole iron source. Collectively, these in vivo results further confirmed that both HmuR and Kgp are involved in the utilization of hemin and hemoglobin in P. gingivalis A7436.

scholarly journals Pseudomonas aeruginosa Cell-to-Cell Signaling Is Required for Virulence in a Model of Acute Pulmonary Infection

2000 ◽  
Vol 68 (7) ◽  
pp. 4331-4334 ◽  
Author(s):  
James P. Pearson ◽  
Matthew Feldman ◽  
Barbara H. Iglewski ◽  
Alice Prince
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Quorum Sensing ◽  
Cell Signaling ◽  
Type Strain ◽  
Pulmonary Infection ◽  
Virulence Genes ◽  
Wild Type Strain ◽  
Wild Type ◽  
Neonatal Mice ◽  
Mutant Strains

ABSTRACT Cell-to-cell signaling controls many virulence genes inPseudomonas aeruginosa. We tested the virulence oflas and rhl quorum-sensing mutants in neonatal mice. A lasI rhlI double mutant was nearly avirulent, and the respective single mutant strains were reduced in virulence compared with the wild-type strain. Quorum sensing plays a role in P. aeruginosa pneumonia in neonatal mice.

scholarly journals Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

2011 ◽  
Vol 77 (20) ◽  
pp. 7247-7254 ◽  
Author(s):  
Holly Snyder ◽  
Hongjun He ◽  
Heather Owen ◽  
Chris Hanna ◽  
Steven Forst
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Infective Juvenile ◽  
Xenorhabdus Nematophila ◽  
Wild Type ◽  
Content Type ◽  
Mutant Strains ◽  
Phenotypic Variant

ABSTRACTXenorhabdus nematophilaengages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show thatX. nematophilagrown on LB agar produced flagella rather than fimbriae. IJs propagated onX. nematophilagrown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized bymrxmutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. Themrxstrains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, themrxstrains displayed a competitive colonization defectin vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or themrxstrain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type andmrxstrains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonizationin vivoand provide new insights into the role of chaperone-usher fimbriae in the life cycle ofX. nematophila.

scholarly journals Bactericidal Activities of BMS-284756, a Novel Des-F(6)-Quinolone, against Staphylococcus aureus Strains with Topoisomerase Mutations

2002 ◽  
Vol 46 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Laura E. Lawrence ◽  
MaryBeth Frosco ◽  
Brenda Ryan ◽  
Susan Chaniewski ◽  
Hyekyung Yang ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
In Vivo Efficacy ◽  
Mutant Strains ◽  
Bactericidal Activities ◽  
Time Kill

ABSTRACT The antistaphylococcal activities of BMS-284756 (T-3811ME), levofloxacin, moxifloxacin, and ciprofloxacin were compared against wild-type and grlA and grlA/gyrA mutant strains of Staphylococcus aureus. BMS-284756 was the most active quinolone tested, with MICs and minimal bactericidal concentrations against S. aureus wild-type strain MT5, grlA mutant MT5224c4, and grlA/gyrA mutant EN8 of 0.03 and 0.06, 0.125 and 0.125, and 4 and 4 μg/ml, respectively. In the time-kill studies, BMS-284756 and levofloxacin exhibited rapid killing against all strains. Ciprofloxacin, however, was not bactericidal for the double mutant, EN8. BMS-284756 and levofloxacin were bactericidal (3 log10 decrease in CFU/ml) against the MT5 and MT5224c4 strains at two and four times the MIC within 2 to 4 h. Against EN8, BMS-284756 was bactericidal within 4 h at two and four times the MIC, and levofloxacin achieved similar results within 4 to 6 h. Both the wild-type strain MT5 and grlA mutant MT5224c4 should be considered susceptible to both BMS-284756 and levofloxacin, and both quinolones are predicted to have clinical efficacy. The in vivo efficacy of BMS-284756, levofloxacin, and moxifloxacin against S. aureus strain ISP794 and its single mutant 2C6(1)-1 directly reflected the in vitro activity: increased MICs correlated with decreased in vivo efficacy. The 50% protective doses of BMS-284756 against wild-type and mutant strains were 2.2 and 1.6 mg/kg of body weight/day, respectively, compared to the levofloxacin values of 16 and 71 mg/kg/day and moxifloxacin values of 4.7 and 61.6 mg/kg/day. BMS-284756 was more potent than levofloxacin and equipotent with moxifloxacin against ISP794 both in vitro and in vivo, while BMS-284756 was more potent than levofloxacin and moxifloxacin against 2C6(1)-1.

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