scholarly journals Diffusible Signal Factor–Repressed Extracellular Traits Enable Attachment of Xylella fastidiosa to Insect Vectors and Transmission

2014 ◽  
Vol 104 (1) ◽  
pp. 27-33 ◽  
Author(s):  
Clelia Baccari ◽  
Nabil Killiny ◽  
Michael Ionescu ◽  
Rodrigo P. P. Almeida ◽  
Steven E. Lindow
Keyword(s):  
Type Strain ◽  
Host Plants ◽  
Wild Type Strain ◽  
Culture Supernatant ◽  
Culture Media ◽  
Xylella Fastidiosa ◽  
Xylem Sap ◽  
Wild Type ◽  
Diffusible Signal Factor ◽  
Type Strains

The hypothesis that a wild-type strain of Xylella fastidiosa would restore the ability of rpfF mutants blocked in diffusible signal factor production to be transmitted to new grape plants by the sharpshooter vector Graphocephala atropunctata was tested. While the rpfF mutant was very poorly transmitted by vectors irrespective of whether they had also fed on plants infected with the wild-type strain, wild-type strains were not efficiently transmitted if vectors had fed on plants infected with the rpfF mutant. About 100-fewer cells of a wild-type strain attached to wings of a vector when suspended in xylem sap from plants infected with an rpfF mutant than in sap from uninfected grapes. The frequency of transmission of cells suspended in sap from plants that were infected by the rpfF mutant was also reduced over threefold. Wild-type cells suspended in a culture supernatant of an rpfF mutant also exhibited 10-fold less adherence to wings than when suspended in uninoculated culture media. A factor released into the xylem by rpfF mutants, and to a lesser extent by the wild-type strain, thus inhibits their attachment to, and thus transmission by, sharpshooter vectors and may also enable them to move more readily through host plants.

scholarly journals Phenotype Overlap in Xylella fastidiosa Is Controlled by the Cyclic Di-GMP Phosphodiesterase Eal in Response to Antibiotic Exposure and Diffusible Signal Factor-Mediated Cell-Cell Signaling

2013 ◽  
Vol 79 (11) ◽  
pp. 3444-3454 ◽  
Author(s):  
Alessandra A. de Souza ◽  
Michael Ionescu ◽  
Clelia Baccari ◽  
Aline M. da Silva ◽  
Steven E. Lindow
Keyword(s):  
Cell Density ◽  
Type Strain ◽  
Deletion Mutant ◽  
Wild Type Strain ◽  
Xylella Fastidiosa ◽  
Wild Type ◽  
Extrinsic Factors ◽  
Content Type ◽  
Diffusible Signal Factor ◽  
Cell Cell

ABSTRACTEal is an EAL domain protein inXylella fastidiosahomologous to one involved in resistance to tobramycin inPseudomonas aeruginosa. EAL and HD-GYP domain proteins are implicated in the hydrolysis of the secondary messenger bis-(3′-5′)-cyclic dimeric GMP (cyclic di-GMP). Cell density-dependent communication mediated by a Diffusible Signal Factor (DSF) also modulates cyclic di-GMP levels inX. fastidiosa, thereby controlling the expression of virulence genes and genes involved in insect transmission. The possible linkage of Eal to both extrinsic factors such as antibiotics and intrinsic factors such as quorum sensing, and whether both affect virulence, was thus addressed. Expression ofealwas induced by subinhibitory concentrations of tobramycin, and anealdeletion mutant was more susceptible to this antibiotic than the wild-type strain and exhibited phenotypes similar to those of anrpfFdeletion mutant blocked in DSF production, such as hypermotility, reduced biofilm formation, and hypervirulence to grape. Consistent with that, therpfFmutant was more susceptible than the wild-type strain to tobramycin. Therefore, we propose that cell-cell communication and antibiotic stress can apparently lead to similar modulations of cyclic di-GMP inX. fastidiosa, resulting in similar phenotypes. However, the effect of cell density is dominant compared to that of antibiotic stress, sinceealis suppressed by RpfF, which may prevent inappropriate behavioral changes in response to antibiotic stress when DSF accumulates.

Development of mutants of Gliocladium virens tolerant to benomyl

1990 ◽  
Vol 36 (7) ◽  
pp. 484-489 ◽  
Author(s):  
G. C. Papavizas ◽  
D. P. Roberts ◽  
K. K. Kim
Keyword(s):  
Carbon Source ◽  
Type Strain ◽  
Wild Type Strain ◽  
Carbon Sources ◽  
Sclerotium Rolfsii ◽  
Wild Type ◽  
Gliocladium Virens ◽  
Rhizosphere Competence ◽  
Filter Paper Cellulase ◽  
Type Strains

Aqueous suspensions of conidia of Gliocladium virens strains Gl-3 and Gl-21 were exposed to both ultraviolet radiation and ethyl methanesulfonate. Two mutants of Gl-3 and three of Gl-21 were selected for tolerance to benomyl at 10 μg∙mL−1, as indicated by growth and conidial germination on benomyl-amended potato dextrose agar. The mutants differed considerably from their respective wild-type strains in appearance, growth habit, sporulation, carbon-source utilization, and enzyme activity profiles. Of 10 carbon sources tested, cellobiose, xylose, and xylan were the best for growth, galactose and glucose were intermediate, and arabinose, ribose, and rhamnose were poor sources of carbon. The wild-type strains and the mutants did not utilize cellulose as the sole carbon source for growth. Two benomyl-tolerant mutants of Gl-3 produced less cellulase (β-1,4-glucosidase, carboxymethylcellulase, filter-paper cellulase) than Gl-3. In contrast, mutants of Gl-21 produced more cellulase than the wild-type strain. Only Gl-3 provided control of blight on snapbean caused by Sclerotium rolfsii. Wild-type strain Gl-21 and all mutants from both strains were ineffective biocontrol agents. Key words: Gliocladium, benomyl tolerance, Sclerotium, rhizosphere competence.

A Stable 44S Intermediate in the Autodigestion of 50S Ribosomal Subunits

1971 ◽  
Vol 29 ◽  
pp. 430-431
Author(s):  
John H. Nisbet ◽  
Henry S. Slayter
Keyword(s):  
Escherichia Coli ◽  
Molecular Weight ◽  
Ribosomal Rna ◽  
Gel Electrophoresis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Ribosomal Subunit ◽  
Wild Type ◽  
Ribosomal Subunits ◽  
Type Strains

Wild - type strains of Escherichia coli are known to contain as many as four endogenous nucleases (Ref. 1). These are commonly found associated with the ribosomes after extraction from the cell, but may be removed, with the exception of RNase IV, by washing the ribosomes in NH4Cl (at 0.2 M and higher concentrations). We have examined the effect of these nucleases on the 50S ribosomal subunit of one wild-type strain, K12 (Hfr 3000), by incubating the unwashed particles at 37° in the presence of varying magnesium concentrations.At 10-4 molar magnesium (slower at 10-3 molar), the 50S particle is converted to a species sedimenting at about 44S. About 20% of the total O.D260 is liberated at the same time. Continued incubation leads to the release of more O.D260 material while the RNA remaining in the 44S (Fig. 1) particle is progressively cleaved, eventually to the point where it consists of one principal fragment of molecular weight 0.42 x 106 daltons and several lesser fragments. The ribosomal RNA and proteins have been characterized by acrylamide gel electrophoresis.

scholarly journals Cell-to-Cell Signaling in Xylella fastidiosa Suppresses Movement and Xylem Vessel Colonization in Grape

2008 ◽  
Vol 21 (10) ◽  
pp. 1309-1315 ◽  
Author(s):  
Subhadeep Chatterjee ◽  
Karyn L. Newman ◽  
Steven E. Lindow
Keyword(s):  
Cell Signaling ◽  
Type Strain ◽  
Laser Scanning ◽  
Wild Type Strain ◽  
Xylella Fastidiosa ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Deficient Mutant ◽  
Wild Type ◽  
Wide Range

Cell-to-cell signaling mediated by a fatty acid diffusible signaling factor (DSF) is central to the regulation of the virulence of Xylella fastidiosa. DSF production by X. fastidiosa is dependent on rpfF and, although required for insect colonization, appears to reduce its virulence to grape. To understand what aspects of colonization of grape are controlled by DSF in X. fastidiosa and, thus, those factors that contribute to virulence, we assessed the colonization of grape by a green fluorescent protein–marked rpfF-deficient mutant. The rpfF-deficient mutant was detected at a greater distance from the point of inoculation than the wild-type strain at a given sampling time, and also attained a population size that was up to 100-fold larger than that of the wild-type strain at a given distance from the point of inoculation. Confocal laser-scanning microscopy revealed that approximately 10-fold more vessels in petioles of symptomatic leaves harbored at least some cells of either the wild type or rpfF mutant when compared with asymptomatic leaves and, thus, that disease symptoms were associated with the extent of vessel colonization. Importantly, the rpfF mutant colonized approximately threefold more vessels than the wild-type strain. Although a wide range of colony sizes were observed in vessels colonized by both the wild type and rpfF mutant, the proportion of colonized vessels harboring large numbers of cells was significantly higher in plants inoculated with the rpfF mutant than with the wild-type strain. These studies indicated that the hypervirulence phenotype of the rpfF mutant is due to both a more extensive spread of the pathogen to xylem vessels and unrestrained multiplication within vessels leading to blockage. These results suggest that movement and multiplication of X. fastidiosa in plants are linked, perhaps because cell wall degradation products are a major source of nutrients. Thus, DSF-mediated cell-to-cell signaling, which restricts movement and colonization of X. fastidiosa, may be an adaptation to endophytic growth of the pathogen that prevents the excessive growth of cells in vessels.

scholarly journals The Secreted Esterase of Propionibacterium freudenreichii Has a Major Role in Cheese Lipolysis

2013 ◽  
Vol 80 (2) ◽  
pp. 751-756 ◽  
Author(s):  
María Claudia Abeijón Mukdsi ◽  
Hélène Falentin ◽  
Marie-Bernadette Maillard ◽  
Victoria Chuat ◽  
Roxana Beatriz Medina ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Type Strain ◽  
Wild Type Strain ◽  
Lipolytic Activity ◽  
Premature Stop Codon ◽  
Propionibacterium Freudenreichii ◽  
Wild Type ◽  
Swiss Cheese ◽  
Content Type ◽  
Type Strains

ABSTRACTFree fatty acids are important flavor compounds in cheese.Propionibacterium freudenreichiiis the main agent of their release through lipolysis in Swiss cheese. Our aim was to identify the esterase(s) involved in lipolysis byP. freudenreichii. We targeted two previously identified esterases: one secreted esterase, PF#279, and one putative cell wall-anchored esterase, PF#774. To evaluate their role in lipolysis, we constructed overexpression and knockout mutants ofP. freudenreichiiCIRM-BIA1Tfor each corresponding gene. The sequences of both genes were also compared in 21 wild-type strains. All strains were assessed for their lipolytic activity on milk fat. The lipolytic activity observed matched data previously reported in cheese, thus validating the relevance of the method used. The mutants overexpressing PF#279 or PF#774 released four times more fatty acids than the wild-type strain, demonstrating that both enzymes are lipolytic esterases. However, inactivation of thepf279gene induced a 75% reduction in the lipolytic activity compared to that of the wild-type strain, whereas inactivation of thepf774gene did not modify the phenotype. Two of the 21 wild-type strains tested did not display any detectable lipolytic activity. Interestingly, these two strains exhibited the same single-nucleotide deletion at the beginning of thepf279gene sequence, leading to a premature stop codon, whereas they harbored apf774gene highly similar to that of the other strains. Taken together, these results clearly demonstrate that PF#279 is the main lipolytic esterase inP. freudenreichiiand a key agent of Swiss cheese lipolysis.

scholarly journals Fitness Cost of Rifampin Resistance in Neisseria meningitidis:In VitroStudy of Mechanisms Associated withrpoBH553Y Mutation

2015 ◽  
Vol 59 (12) ◽  
pp. 7637-7649 ◽  
Author(s):  
Roberta Colicchio ◽  
Chiara Pagliuca ◽  
Gabiria Pastore ◽  
Annunziata Gaetana Cicatiello ◽  
Caterina Pagliarulo ◽  
...  
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Capsular Polysaccharide ◽  
Culture Media ◽  
Point Mutations ◽  
Clinical Isolates ◽  
Sequencing Analysis ◽  
Wild Type ◽  
Rifampin Resistance

ABSTRACTRifampin chemoprophylaxis againstNeisseria meningitidisinfections led to the onset of rifampin resistance in clinical isolates harboring point mutations in therpoBgene, coding for the RNA polymerase β chain. These resistant strains are rare in medical practice, suggesting their decreased fitness in the human host. In this study, we isolated rifampin-resistantrpoBmutants from hypervirulent serogroup C strain 93/4286 and analyzed their different properties, including the ability to grow/survive in different culture media and in differentiated THP-1 human monocytes and to compete with the wild-type strainin vitro. Our results demonstrate that differentrpoBmutations (H553Y, H553R, and S549F) may have different effects, ranging from low- to high-cost effects, on bacterial fitnessin vitro. Moreover, we found that the S549F mutation confers temperature sensitivity, possibly explaining why it is observed very rarely in clinical isolates. Comparative high-throughput RNA sequencing analysis of bacteria grown in chemically defined medium demonstrated that the low-cost H553Y substitution resulted in global transcriptional changes that functionally mimic the stringent response. Interestingly, many virulence-associated genes, including those coding for meningococcal type IV pili, porin A, adhesins/invasins, IgA protease, two-partner secretion system HrpA/HrpB, enzymes involved in resistance to oxidative injury, lipooligosaccharide sialylation, and capsular polysaccharide biosynthesis, were downregulated in the H553Y mutant compared to their level of expression in the wild-type strain. These data might account for the reduced capacity of this mutant to grow/survive in differentiated THP-1 cells and explain the rarity of H553Y mutants among clinical isolates.

scholarly journals Mutations in the lspA1 and lspA2 Genes of Haemophilus ducreyi Affect the Virulence of This Pathogen in an Animal Model System

2003 ◽  
Vol 71 (5) ◽  
pp. 2478-2486 ◽  
Author(s):  
Christine K. Ward ◽  
Jo L. Latimer ◽  
Joseph Nika ◽  
Merja Vakevainen ◽  
Jason R. Mock ◽  
...  
Keyword(s):  
Animal Model ◽  
Parent Strain ◽  
Type Strain ◽  
Double Mutant ◽  
Wild Type Strain ◽  
Culture Supernatant ◽  
Haemophilus Ducreyi ◽  
Supernatant Fluid ◽  
Wild Type ◽  
Wild Type Parent

ABSTRACT Haemophilus ducreyi 35000HP contains two genes, lspA1 and lspA2, whose predicted protein products have molecular weights of 456,000 and 543,000, respectively (C. K. Ward, S. R. Lumbley, J. L. Latimer, L. D. Cope, and E. J. Hansen, J. Bacteriol. 180:6013-6022, 1998). We have constructed three H. ducreyi 35000HP mutants containing antibiotic resistance cartridges in one or both of the lspA1 and lspA2 open reading frames. Western blot analysis using LspA1- and LspA2-specific monoclonal antibodies indicated that the wild-type parent strain 35000HP expressed LspA1 protein that was readily detectable in culture supernatant fluid together with a barely detectable amount of LspA2 protein. The lspA2 mutant 35000HP.2 expressed LspA1 protein that was detectable in culture supernatant fluid and no LspA2 protein. In contrast, the H. ducreyi lspA1 mutant 35000HP.1, which did not express the LspA1 protein, expressed a greater quantity of the LspA2 protein than did the wild-type parent strain. The lspA1 lspA2 double mutant 35000HP.12 expressed neither LspA1 nor LspA2. The three mutant strains adhered to human foreskin fibroblasts and to a human keratinocyte cell line in vitro at a level that was not significantly different from that of the wild-type strain 35000HP. Lack of expression of the LspA1 protein by both the lspA1 mutant and the lspA1 lspA2 double mutant was associated with an increased tendency to autoagglutinate. When evaluated in the temperature-dependent rabbit model for chancroid, the lspA1 lspA2 double mutant was substantially less virulent than the wild-type strain 35000HP. The results of these studies indicated that H. ducreyi requires both the LspA1 and LspA2 proteins to be fully virulent in this animal model for experimental chancroid.

scholarly journals The Role of Ethylene Production in Virulence of Pseudomonas syringae pvs. glycinea and phaseolicola

2001 ◽  
Vol 91 (5) ◽  
pp. 511-518 ◽  
Author(s):  
Helge Weingart ◽  
Henriette Ullrich ◽  
Klaus Geider ◽  
Beate Völksch
Keyword(s):  
Pseudomonas Syringae ◽  
Ethylene Production ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
In Planta ◽  
Population Sizes ◽  
Soybean Plants ◽  
Type Strains

The importance of ethylene production for virulence of Pseudomonas syringae pvs. glycinea and phaseolicola was assayed by comparing bacterial multiplication and symptom development in bean and soybean plants inoculated with ethylene-negative (efe) mutants and wild-type strains. The efe mutants of Pseudomonas syringae pv. glycinea were significantly reduced in their ability to grow in planta. However, the degree of reduction was strain-dependent. Population sizes of efe mutant 16/83-E1 that did not produce the phototoxin coronatine were 10- and 15-fold lower than those of the wild-type strain on soybean and on bean, and 16/83-E1 produced very weak symptoms compared with the wild-type strain. The coronatine-producing efe mutant 7a/90-E1 reached fourfold and twofold lower population sizes compared with the wild-type strain on soybean and bean, respectively, and caused disease symptoms typical of the wild-type strain. Experiments with ethylene-insensitive soybeans confirmed these results. The virulence of the wild-type strains was reduced to the same extent in ethylene-insensitive soybean plants as the virulence of the efe mutants in ethylene-susceptible soybeans. In contrast, the virulence of Pseudomonas syringae pv. phaseolicola was not affected by disruption of the efe gene.

Modulating action of cyclic AMP on the expression of two SOS genes in Escherichia coli K-12

1987 ◽  
Vol 33 (8) ◽  
pp. 704-708 ◽  
Author(s):  
Jordi Barbé ◽  
Isidre Gibert ◽  
Ricardo Guerrero
Keyword(s):  
Escherichia Coli ◽  
Cyclic Amp ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
Cultural Conditions ◽  
Gene Coding ◽  
K 12 ◽  
Type Strains ◽  
Lambda Prophage

Ultraviolet irradiation and cyclic AMP treatment produce a synergistic effect on the induction of the clel gene (coding for bacteriocin ColE1) in wild-type strains of Escherichia coli. On the other hand, cyclic AMP does not affect the uv-mediated induction of the recA, sfiA, and umuDC genes. Growth in the presence of glucose or glycerol does not affect the factor of amplification of the expression of the clel gene in uv-irradiated cells of the wild-type strain. Although, in cultures not treated with uv, the basal level of clel induction is about twice as high in cells grown with glycerol as in those using glucose as carbon source. In recA mutants neither simultaneous nor separate treatments with either cyclic AMP or uv irradiation induced transcription of the clel gene. Moreover, cyclic AMP induced a slight increase in clel gene expression in uv-irradiated cya strains, but not in the crp mutants. Nevertheless, the pattern of the uv-mediated induction of other SOS genes, such as umuDC, was the same in the cya and crp mutants, as in their parental wild-type strains. Furthermore, the uv-mediated induction of lambda prophage was decreased after either addition of cyclic AMP or growth in cultural conditions where the level of this nucleotide was low.

scholarly journals Trehalose Synthesis Contributes to Osmotic Stress Tolerance and Virulence of the Bacterial Wilt Pathogen Ralstonia solanacearum

2020 ◽  
Vol 33 (3) ◽  
pp. 462-473 ◽  
Author(s):  
April M. MacIntyre ◽  
John X. Barth ◽  
Molly C. Pellitteri Hahn ◽  
Cameron O. Scarlett ◽  
Stéphane Genin ◽  
...  
Keyword(s):  
Osmotic Stress ◽  
Bacterial Wilt ◽  
Ralstonia Solanacearum ◽  
Type Strain ◽  
Wild Type Strain ◽  
Xylem Sap ◽  
Wilt Disease ◽  
Wild Type ◽  
Tomato Plants ◽  
Trehalose Synthesis

The xylem-dwelling plant pathogen Ralstonia solanacearum changes the chemical composition of host xylem sap during bacterial wilt disease. The disaccharide trehalose, implicated in stress tolerance across all kingdoms of life, is enriched in sap from R. solanacearum–infected tomato plants. Trehalose in xylem sap could be synthesized by the bacterium, the plant, or both. To investigate the source and role of trehalose metabolism during wilt disease, we evaluated the effects of deleting the three trehalose synthesis pathways in the pathogen: TreYZ, TreS, and OtsAB, as well as its sole trehalase, TreA. A quadruple treY/treS/otsA/treA mutant produced 30-fold less intracellular trehalose than the wild-type strain missing the trehalase enzyme. This trehalose-nonproducing mutant had reduced tolerance to osmotic stress, which the bacterium likely experiences in plant xylem vessels. Following naturalistic soil-soak inoculation of tomato plants, this triple mutant did not cause disease as well as wild-type R. solanacearum. Further, the wild-type strain out-competed the trehalose-nonproducing mutant by over 600-fold when tomato plants were coinoculated with both strains, showing that trehalose biosynthesis helps R. solanacearum overcome environmental stresses during infection. An otsA (trehalose-6-phosphate synthase) single mutant behaved similarly to ΔtreY/treS/otsA in all experimental settings, suggesting that the OtsAB pathway is the dominant trehalose synthesis pathway in R. solanacearum.

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