scholarly journals Decreasing Global Transcript Levels over Time Suggest that Phytoplasma Cells Enter Stationary Phase during Plant and Insect Colonization

2015 ◽  
Vol 81 (7) ◽  
pp. 2591-2602 ◽  
Author(s):  
D. Pacifico ◽  
L. Galetto ◽  
M. Rashidi ◽  
S. Abbà ◽  
S. Palmano ◽  
...  
Keyword(s):  
Stationary Phase ◽  
Target Genes ◽  
Secreted Proteins ◽  
Healthy Plant ◽  
Insect Vector ◽  
Plant Host ◽  
Term Survival ◽  
Transcript Levels ◽  
Content Type ◽  
Macrosteles Quadripunctulatus

ABSTRACTTo highlight different transcriptional behaviors of the phytoplasma in the plant and animal host, expression of 14 genes of “CandidatusPhytoplasma asteris,” chrysanthemum yellows strain, was investigated at different times following the infection of a plant host (Arabidopsis thaliana) and two insect vector species (Macrosteles quadripunctulatusandEuscelidius variegatus). Target genes were selected among those encoding antigenic membrane proteins, membrane transporters, secreted proteins, and general enzymes. Transcripts were detected for all analyzed genes in the three hosts; in particular, those encoding the antigenic membrane protein Amp, elements of the mechanosensitive channel, and two of the four secreted proteins (SAP54 and TENGU) were highly accumulated, suggesting that they play important roles in phytoplasma physiology during the infection cycle. Most transcripts were present at higher abundance in the plant host than in the insect hosts. Generally, transcript levels of the selected genes decreased significantly during infection ofA. thalianaandM. quadripunctulatusbut were more constant inE. variegatus. Such decreases may be explained by the fact that only a fraction of the phytoplasma population was transcribing, while the remaining part was aging to a stationary phase. This strategy might improve long-term survival, thereby increasing the likelihood that the pathogen may be acquired by a vector and/or inoculated to a healthy plant.

scholarly journals The Bacterium Pantoea stewartii Uses Two Different Type III Secretion Systems To Colonize Its Plant Host and Insect Vector

2012 ◽  
Vol 78 (17) ◽  
pp. 6327-6336 ◽  
Author(s):  
Valdir R. Correa ◽  
Doris R. Majerczak ◽  
El-Desouky Ammar ◽  
Massimo Merighi ◽  
Richard C. Pratt ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Flea Beetle ◽  
Insect Vector ◽  
Secretion Systems ◽  
Plant Host ◽  
Content Type ◽  
Type Iii ◽  
Pantoea Stewartii ◽  
Type Iii Secretion Systems ◽  
Animal Pathogens

ABSTRACTPlant- and animal-pathogenic bacteria utilize phylogenetically distinct type III secretion systems (T3SS) that produce needle-like injectisomes or pili for the delivery of effector proteins into host cells.Pantoea stewartiisubsp.stewartii(herein referred to asP. stewartii), the causative agent of Stewart's bacterial wilt and leaf blight of maize, carries phylogenetically distinct T3SSs. In addition to an Hrc-Hrp T3SS, known to be essential for maize pathogenesis,P. stewartiihas a second T3SS (Pantoeasecretion island 2 [PSI-2]) that is required for persistence in its flea beetle vector,Chaetocnema pulicaria(Melsh). PSI-2 belongs to the Inv-Mxi-Spa T3SS family, typically found in animal pathogens. Mutagenesis of the PSI-2psaNgene, which encodes an ATPase essential for secretion of T3SS effectors by the injectisome, greatly reduces both the persistence ofP. stewartiiin flea beetle guts and the beetle's ability to transmitP. stewartiito maize. Ectopic expression of thepsaNgene complements these phenotypes. In addition, the PSI-2psaNgene is not required forP. stewartiipathogenesis of maize and is transcriptionally upregulated in insects compared to maize tissues. Thus, the Hrp and PSI-2 T3SSs play different roles in the life cycle ofP. stewartiias it alternates between its insect vector and plant host.

scholarly journals DksA and ppGpp Regulate the σS Stress Response by Activating Promoters for the Small RNA DsrA and the Anti-Adapter Protein IraP

2017 ◽  
Vol 200 (2) ◽  
Author(s):  
Mary E. Girard ◽  
Saumya Gopalkrishnan ◽  
Elicia D. Grace ◽  
Jennifer A. Halliday ◽  
Richard L. Gourse ◽  
...  
Keyword(s):  
Stress Response ◽  
Rna Polymerase ◽  
Stationary Phase ◽  
Sigma Factor ◽  
Bacterial Species ◽  
Adaptor Protein ◽  
Large Family ◽  
Alternative Sigma Factor ◽  
Term Survival ◽  
Content Type

ABSTRACT σS is an alternative sigma factor, encoded by the rpoS gene, that redirects cellular transcription to a large family of genes in response to stressful environmental signals. This so-called σS general stress response is necessary for survival in many bacterial species and is controlled by a complex, multifactorial pathway that regulates σS levels transcriptionally, translationally, and posttranslationally in Escherichia coli. It was shown previously that the transcription factor DksA and its cofactor, ppGpp, are among the many factors governing σS synthesis, thus playing an important role in activation of the σS stress response. However, the mechanisms responsible for the effects of DksA and ppGpp have not been elucidated fully. We describe here how DksA and ppGpp directly activate the promoters for the anti-adaptor protein IraP and the small regulatory RNA DsrA, thereby indirectly influencing σS levels. In addition, based on effects of DksAN88I, a previously identified DksA variant with increased affinity for RNA polymerase (RNAP), we show that DksA can increase σS activity by another indirect mechanism. We propose that by reducing rRNA transcription, DksA and ppGpp increase the availability of core RNAP for binding to σS and also increase transcription from other promoters, including PdsrA and PiraP. By improving the translation and stabilization of σS, as well as the ability of other promoters to compete for RNAP, DksA and ppGpp contribute to the switch in the transcription program needed for stress adaptation. IMPORTANCE Bacteria spend relatively little time in log phase outside the optimized environment found in a laboratory. They have evolved to make the most of alternating feast and famine conditions by seamlessly transitioning between rapid growth and stationary phase, a lower metabolic mode that is crucial for long-term survival. One of the key regulators of the switch in gene expression that characterizes stationary phase is the alternative sigma factor σS. Understanding the factors governing σS activity is central to unraveling the complexities of growth, adaptation to stress, and pathogenesis. Here, we describe three mechanisms by which the RNA polymerase binding factor DksA and the second messenger ppGpp regulate σS levels.

scholarly journals Culture Volume and Vessel Affect Long-Term Survival, Mutation Frequency, and Oxidative Stress of Escherichia coli

2013 ◽  
Vol 80 (5) ◽  
pp. 1732-1738 ◽  
Author(s):  
Karin E. Kram ◽  
Steven E. Finkel
Keyword(s):  
Oxidative Stress ◽  
Escherichia Coli ◽  
Stationary Phase ◽  
Mutation Frequency ◽  
Physiological Responses ◽  
Culture Vessel ◽  
Term Survival ◽  
Long Term Survival ◽  
Content Type

ABSTRACTBacteria such asEscherichia coliare frequently studied during exponential- and stationary-phase growth. However, many strains can survive in long-term stationary phase (LTSP), without the addition of nutrients, from days to several years. During LTSP, cells experience a variety of stressors, including reactive oxidative species, nutrient depletion, and metabolic toxin buildup, that lead to physiological responses and changes in genetic stability. In this study, we monitored survival during LTSP, as well as reporters of genetic and physiological change, to determine how the physical environment affectsE. coliduring long-term batch culture. We demonstrate differences in yield during LTSP in cells incubated in LB medium in test tubes versus Erlenmeyer flasks, as well as growth in different volumes of medium. We determined that these differences are only partially due to differences in oxygen levels by incubating the cells in different volumes of media under anaerobic conditions. Since we hypothesized that differences in long-term survival are the result of changes in physiological outputs during the late log and early stationary phases, we monitored alkalization, mutation frequency, oxidative stress response, and glycation. Although initial cell yields are essentially equivalent under each condition tested, physiological responses vary greatly in response to culture environment. Incubation in lower-volume cultures leads to higheroxyRexpression but lower mutation frequency and glycation levels, whereas incubation in high-volume cultures has the opposite effect. We show here that even under commonly used experimental conditions that are frequently treated as equivalent, the stresses experienced by cells can differ greatly, suggesting that culture vessel and incubation conditions should be carefully considered in the planning or analysis of experiments.

scholarly journals Variable Membrane Protein A of Flavescence Dorée Phytoplasma Binds the Midgut Perimicrovillar Membrane ofEuscelidius variegatusand Promotes Adhesion to Its Epithelial Cells

2018 ◽  
Vol 84 (8) ◽  
pp. e02487-17 ◽  
Author(s):  
Nathalie Arricau-Bouvery ◽  
Sybille Duret ◽  
Marie-Pierre Dubrana ◽  
Brigitte Batailler ◽  
Delphine Desqué ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Salivary Glands ◽  
Plant Pathogens ◽  
Insect Cells ◽  
Wild Plants ◽  
Insect Vector ◽  
Plant Host ◽  
Content Type ◽  
Flavescence Dorée ◽  
Fluorescent Beads

ABSTRACTPhytoplasmas are uncultivated plant pathogens and cell wall-less bacteria and are transmitted from plant to plant by hemipteran insects. The phytoplasma's circulative propagative cycle in insects requires the crossing of the midgut and salivary glands, and primary adhesion to cells is an initial step toward the invasion process. The flavescence dorée (FD) phytoplasma possesses a set of variable membrane proteins (Vmps) exposed on its surface, and this pathogen is suspected to interact with insect cells. The results showed that VmpA is expressed by the flavescence dorée phytoplasma present in the midgut and salivary glands. Phytoplasmas cannot be cultivated at present, and no mutant can be produced to investigate the putative role of Vmps in the adhesion of phytoplasma to insect cells. To overcome this difficulty, we engineered theSpiroplasma citrimutant G/6, which lacks the ScARP adhesins, for VmpA expression and used VmpA-coated fluorescent beads to determine if VmpA acts as an adhesin inex vivoadhesion assays andin vivoingestion assays. VmpA specifically interacted withEuscelidiusvariegatusinsect cells in culture and promoted the retention of VmpA-coated beads to the midgut ofE. variegatus. In this latest case, VmpA-coated fluorescent beads were localized and embedded in the perimicrovillar membrane of the insect midgut. Thus, VmpA functions as an adhesin that could be essential in the colonization of the insect by the FD phytoplasmas.IMPORTANCEPhytoplasmas infect a wide variety of plants, ranging from wild plants to cultivated species, and are transmitted by different leafhoppers, planthoppers, and psyllids. The specificity of the phytoplasma-insect vector interaction has a major impact on the phytoplasma plant host range. As entry into insect cells is an obligate process for phytoplasma transmission, the bacterial adhesion to insect cells is a key step. Thus, studying surface-exposed proteins of phytoplasma will help to identify the adhesins implicated in the specific recognition of insect vectors. In this study, it is shown that the membrane protein VmpA of the flavescence dorée (FD) phytoplasma acts as an adhesin that is able to interact with cells ofEuscelidiusvariegatus, the experimental vector of the FD phytoplasma.

scholarly journals Long-Term Survival of Borrelia burgdorferi Lacking the Hibernation Promotion Factor Homolog in the Unfed Tick Vector

2015 ◽  
Vol 83 (12) ◽  
pp. 4800-4810 ◽  
Author(s):  
Lisa Fazzino ◽  
Kit Tilly ◽  
Daniel P. Dulebohn ◽  
Patricia A. Rosa
Keyword(s):  
Borrelia Burgdorferi ◽  
Stationary Phase ◽  
Bacterial Species ◽  
Protein Secondary Structure ◽  
Mammalian Host ◽  
Term Survival ◽  
Content Type ◽  
Protein Levels ◽  
And Function

Borrelia burgdorferi, a causative agent of Lyme borreliosis, is a zoonotic pathogen that survives in nutrient-limited environments within a tick, prior to transmission to its mammalian host. Survival under these prolonged nutrient-limited conditions is thought to be similar to survival during stationary phase, which is characterized by growth cessation and decreased protein production. Multiple ribosome-associated proteins are implicated in stationary-phase survival ofEscherichia coli. These proteins include hibernation-promoting factor (HPF), which dimerizes ribosomes and prevents translation of mRNA. Bioinformatic analyses indicate thatB. burgdorferiharbors anhpfhomolog, thebb0449gene. BB0449 protein secondary structure modeling also predicted HPF-like structure and function. However, BB0449 protein was not localized in the ribosome-associated protein fraction ofin vitro-grownB. burgdorferi. In wild-typeB. burgdorferi,bb0449transcript and BB0449 protein levels are low during various growth phases. These results are inconsistent with patterns of synthesis of HPF-like proteins in other bacterial species. In addition, two independently derivedbb0449mutants successfully completed the mouse-tick infectious cycle, indicating thatbb0449is not required for prolonged survival in the nutrient-limited environment in the unfed tick or any other stage of infection byB. burgdorferi. We suggest either that BB0449 is associated with ribosomes under specific conditions not yet identified or that BB0449 ofB. burgdorferihas a function other than ribosome conformation modulation.

scholarly journals Dynamics of Metabolic Activities and Gene Expression in the Roseobacter Clade Bacterium Phaeobacter sp. Strain MED193 during Growth with Thiosulfate

2014 ◽  
Vol 80 (22) ◽  
pp. 6933-6942 ◽  
Author(s):  
Saraladevi Muthusamy ◽  
Federico Baltar ◽  
José M. González ◽  
Jarone Pinhassi
Keyword(s):  
Gene Expression ◽  
Stationary Phase ◽  
Sulfur Oxidation ◽  
Active Growth ◽  
Additional Energy ◽  
Term Survival ◽  
Content Type ◽  
Important Pathway ◽  
Metabolic Activities

ABSTRACTMetagenomic analyses of surface seawater reveal that genes for sulfur oxidation are widespread in bacterioplankton communities. However, little is known about the metabolic processes used to exploit the energy potentially gained from inorganic sulfur oxidation in oxic seawater. We therefore studied thesoxgene system containingRoseobacterclade isolatePhaeobactersp. strain MED193 in acetate minimal medium with and without thiosulfate. The addition of thiosulfate enhanced the bacterial growth yields up to 40% in this strain. Concomitantly,soxBandsoxYgene expression increased about 8-fold with thiosulfate and remained 11-fold higher than that in controls through stationary phase. At stationary phase, thiosulfate stimulated protein synthesis and anaplerotic CO2fixation rates up to 5- and 35-fold, respectively. Several genes involved in anaplerotic CO2fixation (i.e., pyruvate carboxylase, propionyl coenzyme A [CoA], and crotonyl-CoA carboxylase) were highly expressed during active growth, coinciding with high CO2fixation rates. The high expression of key genes in the ethylmalonyl-CoA pathway suggests that this is an important pathway for the utilization of two-carbon compounds inPhaeobactersp. MED193. Overall, our findings imply thatRoseobacterclade bacteria carryingsoxgenes can use their lithotrophic potential to gain additional energy from sulfur oxidation for both increasing their growth capacity and improving their long-term survival.

Dual-isotope single-photon emission computerized tomography scanning in patients with glioblastoma multiforme: association with patient survival and histopathological characteristics of tumor after high-dose radiotherapy

1998 ◽  
Vol 89 (1) ◽  
pp. 60-68 ◽  
Author(s):  
Richard B. Schwartz ◽  
B. Leonard Holman ◽  
Joseph F. Polak ◽  
Basem M. Garada ◽  
Marc S. Schwartz ◽  
...  
Keyword(s):  
Survival Rate ◽  
Glioblastoma Multiforme ◽  
Single Photon ◽  
Photon Emission ◽  
High Dose ◽  
Term Survival ◽  
Content Type ◽  
Dual Isotope ◽  
Fine Print

Object. The study was conducted to determine the association between dual-isotope single-photon emission computerized tomography (SPECT) scanning and histopathological findings of tumor recurrence and survival in patients treated with high-dose radiotherapy for glioblastoma multiforme. Methods. Studies in which SPECT with 201Tl and 99mTc-hexamethypropyleneamine oxime (HMPAO) were used were performed 1 day before reoperation in 47 patients with glioblastoma multiforme who had previously been treated by surgery and high-dose radiotherapy. Maximum uptake of 201Tl in the lesion was expressed as a ratio to that in the contralateral scalp, and uptake of 99mTc-HMPAO was expressed as a ratio to that in the cerebellar cortex. Patients were stratified into groups based on the maximum radioisotope uptake values in their tumor beds. The significance of differences in patient gender, histological characteristics of tissue at reoperation, and SPECT uptake group with respect to 1-year survival was elucidated by using the chi-square statistic. Comparisons of patient ages and time to tumor recurrence as functions of 1-year survival were made using the t-test. Survival data at 1 year were presented according to the Kaplan—Meier method, and the significance of potential differences was evaluated using the log-rank method. The effects of different variables (tumor type, time to recurrence, and SPECT grouping) on long-term survival were evaluated using Cox proportional models that controlled for age and gender. All patients in Group I (201Tl ratio < 2 and 99mTc-HMPAO ratio < 0.5) showed radiation changes in their biopsy specimens: they had an 83.3% 1-year survival rate. Group II patients (201T1 ratio < 2 and 99mTc-HMPAO ratio of ≥ 0.5 or 201Tl ratio between 2 and 3.5 regardless of 99mTc-HMPAO ratio) had predominantly infiltrating tumor (66.6%); they had a 29.2% 1-year survival rate. Almost all of the patients in Group III (201Tl ratio > 3.5 and 99mTc-HMPAO ratio ≥ 0.5) had solid tumor (88.2%) and they had a 6.7% 1-year survival rate. Histological data were associated with 1-year survival (p < 0.01); however, SPECT grouping was more closely associated with 1-year survival (p < 0.001) and was the only variable significantly associated with long-term survival (p < 0.005). Conclusions. Dual-isotope SPECT data correlate with histopathological findings made at reoperation and with survival in patients with malignant gliomas after surgical and high-dose radiation therapy.

Tumor recurrence and survival following gamma knife surgery for brain metastases

2005 ◽  
Vol 102 (Special_Supplement) ◽  
pp. 287-288 ◽  
Author(s):  
Thomas Mindermann
Keyword(s):  
Brain Metastasis ◽  
Brain Metastases ◽  
Gamma Knife ◽  
Tumor Recurrence ◽  
Patient Survival ◽  
Gamma Knife Surgery ◽  
Recurrence Rates ◽  
Term Survival ◽  
Content Type ◽  
Fine Print

Object. The authors evaluated prognostic factors for tumor recurrence and patient survival following gamma knife surgery (GKS) for brain metastasis. Methods. A retrospective review of 101 patient charts was undertaken for those patients treated with GKS for brain metastases from 1994 to 2001. Recurrence rates of brain metastasis following GKS depended on the duration of patient survival. Long-term survival was associated with a higher risk of tumor recurrence and shorter-term survival was associated with a lower risk. The duration of survival following GKS for brain metastases seems to be characteristic of the primary disease rather than the cerebral disease. Conclusions. Recurrence rates of brain metastasis following GKS are related to duration of survival, which is in turn mostly dependent on the nature and course of the primary tumor.

scholarly journals Function of the Pyruvate Oxidase-Lactate Oxidase Cascade in Interspecies Competition between Streptococcus oligofermentans and Streptococcus mutans

2012 ◽  
Vol 78 (7) ◽  
pp. 2120-2127 ◽  
Author(s):  
Lei Liu ◽  
Huichun Tong ◽  
Xiuzhu Dong
Keyword(s):  
Stationary Phase ◽  
Streptococcus Mutans ◽  
Growth Phase ◽  
Large Degree ◽  
Interspecies Interactions ◽  
Lactate Oxidase ◽  
Interspecies Competition ◽  
Pyruvate Oxidase ◽  
Content Type

ABSTRACTComplex interspecies interactions occur constantly between oral commensals and the opportunistic pathogenStreptococcus mutansin dental plaque. Previously, we showed that oral commensalStreptococcus oligofermentanspossesses multiple enzymes for H2O2production, especially lactate oxidase (Lox), allowing it to out-competeS. mutans. In this study, through extensive biochemical and genetic studies, we identified a pyruvate oxidase (pox) gene inS. oligofermentans. Apoxdeletion mutant completely lost Pox activity, while ectopically expressedpoxrestored activity. Pox was determined to produce most of the H2O2in the earlier growth phase and log phase, while Lox mainly contributed to H2O2production in stationary phase. Bothpoxandloxwere expressed throughout the growth phase, while expression of theloxgene increased by about 2.5-fold when cells entered stationary phase. Since lactate accumulation occurred to a large degree in stationary phase, the differential Pox- and Lox-generated H2O2can be attributed to differential gene expression and substrate availability. Interestingly, inactivation ofpoxcauses a dramatic reduction in H2O2production from lactate, suggesting a synergistic action of the two oxidases in converting lactate into H2O2. In anin vitrotwo-species biofilm experiment, thepoxmutant ofS. oligofermentansfailed to inhibitS. mutanseven thoughloxwas active. In summary,S. oligofermentansdevelops a Pox-Lox synergy strategy to maximize its H2O2formation so as to win the interspecies competition.

scholarly journals Basal Body Structures Differentially Affect Transcription of RpoN- and FliA-Dependent Flagellar Genes in Helicobacter pylori

2015 ◽  
Vol 197 (11) ◽  
pp. 1921-1930 ◽  
Author(s):  
Jennifer Tsang ◽  
Timothy R. Hoover
Keyword(s):  
Helicobacter Pylori ◽  
Basal Body ◽  
Protein Interactions ◽  
Transcript Levels ◽  
Content Type ◽  
Genes Encoding ◽  
H Pylori ◽  
Flagellar Biogenesis ◽  
Flagellar Genes

ABSTRACTFlagellar biogenesis inHelicobacter pyloriis regulated by a transcriptional hierarchy governed by three sigma factors, RpoD (σ80), RpoN (σ54), and FliA (σ28), that temporally coordinates gene expression with the assembly of the flagellum. Previous studies showed that loss of flagellar protein export apparatus components inhibits transcription of flagellar genes. The FlgS/FlgR two-component system activates transcription of RpoN-dependent genes though an unknown mechanism. To understand better the extent to which flagellar gene regulation is coupled to flagellar assembly, we disrupted flagellar biogenesis at various points and determined how these mutations affected transcription of RpoN-dependent (flaBandflgE) and FliA-dependent (flaA) genes. The MS ring (encoded byfliF) is one of the earliest flagellar structures assembled. Deletion offliFresulted in the elimination of RpoN-dependent transcripts and an ∼4-fold decrease inflaAtranscript levels. FliH is a cytoplasmic protein that functions with the C ring protein FliN to shuttle substrates to the export apparatus. Deletions offliHand genes encoding C ring components (fliMandfliY) decreased transcript levels offlaBandflgEbut had little or no effect on transcript levels offlaA. Transcript levels offlaBandflgEwere elevated in mutants where genes encoding rod proteins (fliEandflgBC) were deleted, while transcript levels offlaAwas reduced ∼2-fold in both mutants. We propose that FlgS responds to an assembly checkpoint associated with the export apparatus and that FliH and one or more C ring component assist FlgS in engaging this flagellar structure.IMPORTANCEThe mechanisms used by bacteria to couple transcription of flagellar genes with assembly of the flagellum are poorly understood. The results from this study identified components of theH. pyloriflagellar basal body that either positively or negatively affect expression of RpoN-dependent flagellar genes. Some of these basal body proteins may interact directly with regulatory proteins that control transcription of theH. pyloriRpoN regulon, a hypothesis that can be tested by examining protein-protein interactionsin vitro.

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