scholarly journals Transition of Vibrio cholerae through a natural host induces resistance to environmental changes

2021 ◽  
Author(s):  
Jamie S Depelteau ◽  
Ronald Limpens ◽  
Dhrubajyoti Nag ◽  
Bjorn E.V. Koch ◽  
Jeffrey H Withey ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Structural Changes ◽  
Environmental Changes ◽  
Diarrheal Disease ◽  
Electron Tomography ◽  
Morphological Characteristics ◽  
Natural Host ◽  
Fluorescent Light ◽  
Uniform Distance ◽  
Environmental Transitions

The pandemic related strains of Vibrio cholerae are known to cause diarrheal disease in animal hosts. These bacteria must overcome rapid changes in their environment, such as the transition from fresh water to the gastrointestinal system of their host. To study the morphological adjustments during environmental transitions, we used zebrafish as a natural host. Using a combination of fluorescent light microscopy, cryogenic electron tomography and serial block face scanning electron microscopy, we studied the structural changes that occur during the infection cycle. We show that the transition from an artificial nutrient rich environment to a nutrient poor environment has a dramatic impact on the cell shape, most notably membrane dehiscence. In contrast, excreted bacteria from the host retain a uniform distance between the membranes as well as their vibrioid shape. Inside the intestine, V. cholerae cells predominantly colonized the anterior to midgut, forming microcolonies associated with the microvilli as well as within the lumen. The cells retained their vibrioid shape but changed their cell length depending on their localization. Our results demonstrate dynamic changes in morphological characteristics of V. cholerae during the transition between the different environments, and we propose that these structural changes are critical for the pathogens ability to colonize host tissues.

scholarly journals Characterization of the Immune Response to Vibrio cholerae Infection in a Natural Host Model

2021 ◽  
Vol 11 ◽  
Author(s):  
Dustin A. Farr ◽  
Dhrubajyoti Nag ◽  
Jeffrey H. Withey
Keyword(s):  
Immune Response ◽  
Vibrio Cholerae ◽  
Diarrheal Disease ◽  
Natural Host ◽  
Zebrafish Model ◽  
Mucin Production ◽  
Immunological Markers ◽  
Contaminated Food ◽  
Life Threatening ◽  
El Tor

The gram-negative bacterium Vibrio cholerae causes the life-threatening diarrheal disease cholera, which is spread through the ingestion of contaminated food or water. Cholera epidemics occur largely in developing countries that lack proper infrastructure to treat sewage and provide clean water. Numerous vertebrate fish species have been found to be natural V. cholerae hosts. Based on these findings, zebrafish (Danio rerio) have been developed as a natural host model for V. cholerae. Diarrheal symptoms similar to those seen in humans are seen in zebrafish as early as 6 hours after exposure. Our understanding of basic zebrafish immunology is currently rudimentary, and no research has been done to date exploring the immune response of zebrafish to V. cholerae infection. In the present study, zebrafish were infected with either pandemic El Tor or non-pandemic, environmental V. cholerae strains and select immunological markers were assessed to determine cellular immunity and humoral immunity. Significant increases in the gene expression of two transcription factors, T-bet and GATA3, were observed in response to infection with both V. cholerae strains, as were levels of mucosal related antibodies. Additionally, the cytokine IL-13 was shown to be significantly elevated and paralleled the mucin output in zebrafish excretions, strengthening our knowledge of IL-13 induced mucin production in cholera. The data presented here further solidify the relevancy of the zebrafish model in studying V. cholerae, as well as expanding its utility in the field of cholera immunology.

scholarly journals The VarA-CsrA regulatory pathway influences cell shape in Vibrio cholerae

2021 ◽  
Author(s):  
Leonardo F. Lemos Rocha ◽  
Katharina Peters ◽  
Jamie S. Depelteau ◽  
Ariane Briegel ◽  
Waldemar Vollmer ◽  
...  
Keyword(s):  
Cell Wall ◽  
Vibrio Cholerae ◽  
Environmental Changes ◽  
Diarrheal Disease ◽  
Spherical Shape ◽  
Building Blocks ◽  
Diaminopimelic Acid ◽  
Two Component Signal Transduction ◽  
External Stimuli ◽  
Mutant Cells

AbstractDespite extensive studies on the curve-shaped bacterium Vibrio cholerae, the causative agent of the diarrheal disease cholera, its virulence-associated regulatory two-component signal transduction system VarS/VarA is not well understood. This pathway, which mainly signals through the downstream protein CsrA, is highly conserved among gamma-proteobacteria, indicating there is likely a broader function of this system beyond virulence regulation. In this study, we investigated the VarA-CsrA signaling pathway and discovered a previously unrecognized link to the shape of the bacterium. We observed that varA-deficient V. cholerae cells showed an abnormal spherical morphology during late-stage growth. Through peptidoglycan (PG) composition analyses, we discovered that these mutant bacteria contained an increased content of disaccharide dipeptides and reduced peptide crosslinks, consistent with the atypical cellular shape. The spherical shape correlated with the CsrA-dependent overproduction of aspartate ammonia lyase (AspA) in varA mutant cells, which likely depleted the cellular aspartate pool; therefore, the synthesis of the PG precursor amino acid meso-diaminopimelic acid was impaired. Importantly, this phenotype, and the overall cell rounding, could be prevented by means of cell wall recycling. Collectively, our data provide new insights into how V. cholerae use the VarA-CsrA signaling system to adjust its morphology upon unidentified external cues in its environment.Significance StatementResponsible for the diarrheal disease cholera, the bacterium Vibrio cholerae tightly regulates its virulence program according to external stimuli. Here, we discovered that a sensing-response mechanism involved in the regulation of virulence also controls bacterial shape. We show that V. cholerae lacking this system lose their normal comma shape and become spherical due to an abnormal cell wall composition caused by metabolic changes that reduce available cell wall building blocks. Our study therefore sheds new light on how V. cholerae modulates its morphology based on environmental changes.

scholarly journals Zebrafish as a Natural Host Model for Vibrio cholerae Colonization and Transmission

2013 ◽  
Vol 80 (5) ◽  
pp. 1710-1717 ◽  
Author(s):  
Donna L. Runft ◽  
Kristie C. Mitchell ◽  
Basel H. Abuaita ◽  
Jonathan P. Allen ◽  
Sarah Bajer ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Intestinal Tract ◽  
Diarrheal Disease ◽  
Close Contact ◽  
Natural Habitat ◽  
Natural Host ◽  
Aquatic Life ◽  
Content Type ◽  
Environmental Survival ◽  
El Tor

ABSTRACTThe human diarrheal disease cholera is caused by the aquatic bacteriumVibrio cholerae.V. choleraein the environment is associated with several varieties of aquatic life, including insect egg masses, shellfish, and vertebrate fish. Here we describe a novel animal model forV. cholerae, the zebrafish. PandemicV. choleraestrains specifically colonize the zebrafish intestinal tract after exposure in water with no manipulation of the animal required. Colonization occurs in close contact with the intestinal epithelium and mimics colonization observed in mammals. Zebrafish that are colonized byV. choleraetransmit the bacteria to naive fish, which then become colonized. Striking differences in colonization betweenV. choleraeclassical and El Tor biotypes were apparent. The zebrafish natural habitat in Asia heavily overlaps areas where cholera is endemic, suggesting that zebrafish andV. choleraeevolved in close contact with each other. Thus, the zebrafish provides a natural host model for the study ofV. choleraecolonization, transmission, and environmental survival.

scholarly journals Pathological transitions in myelin membranes driven by environmental and multiple sclerosis conditions

2018 ◽  
Vol 115 (44) ◽  
pp. 11156-11161 ◽  
Author(s):  
Rona Shaharabani ◽  
Maor Ram-On ◽  
Yeshayahu Talmon ◽  
Roy Beck
Keyword(s):  
Multiple Sclerosis ◽  
Phase Transition ◽  
Lipid Composition ◽  
Environmental Conditions ◽  
Structural Changes ◽  
Environmental Changes ◽  
Hexagonal Phase ◽  
Structural Phase ◽  
Structural Modifications ◽  
Transition Points

Multiple sclerosis (MS) is an autoimmune disease, leading to the destruction of the myelin sheaths, the protective layers surrounding the axons. The etiology of the disease is unknown, although there are several postulated environmental factors that may contribute to it. Recently, myelin damage was correlated to structural phase transition from a healthy stack of lamellas to a diseased inverted hexagonal phase as a result of the altered lipid stoichiometry and low myelin basic protein (MBP) content. In this work, we show that environmental conditions, such as buffer salinity and temperature, induce the same pathological phase transition as in the case of the lipid composition in the absence of MBP. These phase transitions have different transition points, which depend on the lipid’s compositions, and are ion specific. In extreme environmental conditions, we find an additional dense lamellar phase and that the native lipid composition results in similar pathology as the diseased composition. These findings demonstrate that several local environmental changes can trigger pathological structural changes. We postulate that these structural modifications result in myelin membrane vulnerability to the immune system attacks and thus can help explain MS etiology.

scholarly journals First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Mediterranean Fan Palm in Italy

Plant Disease ◽  
2010 ◽  
Vol 94 (1) ◽  
pp. 125-125 ◽  
Author(s):  
G. Polizzi ◽  
D. Aiello ◽  
I. Castello ◽  
V. Guarnaccia ◽  
A. Vitale
Keyword(s):  
Rhizoctonia Solani ◽  
Disease Incidence ◽  
Morphological Characteristics ◽  
Mediterranean Area ◽  
Western Mediterranean ◽  
Fluorescent Light ◽  
Damping Off ◽  
Centraalbureau Voor ◽  
First Report ◽  
Stem Lesions

Mediterranean fan palm (Chamaerops humilis L.), one of just two autochthonous European palms, is native to the western Mediterranean Region in southwestern Europe and northwestern Africa. It can be found growing wild in the Mediterranean area. In Europe, this species is very popular as an ornamental plant. In March 2009, a widespread damping-off was observed in a stock of approximately 30,000 potted 1-month-old plants of C. humilis cv. Vulcano in a nursery in eastern Sicily. Disease incidence was approximately 20%. Disease symptoms consisted of lesions at the seedling shoot (plumule). Stem lesions were initially orange, turned brown, and followed by death of the entire plumule or eophyll. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently isolated from lesions when plated on potato dextrose agar (PDA) amended with streptomycin sulfate at 100 μg/ml. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells removed from cultures grown at 25°C on 2% water agar were determined to be multinucleate when stained with 1% safranin O and 3% KOH solution (1) and examined at ×400. Anastomosis groups were determined by pairing isolates with tester strains AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, and AG-11 on 2% water agar in petri plates (3). Anastomosis was observed only with tester isolates of AG-4, giving both C2 and C3 reactions (2). One representative isolate obtained from symptomatic tissues was deposited at the Fungal Biodiversity Centre, Centraalbureau voor Schimmelcultures (CBS No. 125095). Pathogenicity tests were performed on container-grown, healthy, 1-month-old seedlings. Twenty plants of C. humilis cv. Vulcano were inoculated near the base of the stem with two 1-cm2 PDA plugs from 5-day-old mycelial cultures. The same number of plants served as uninoculated controls. Plants were incubated in a growth chamber and maintained at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Symptoms identical to those observed in the nursery appeared 5 days after inoculation and all plants died within 20 days. No disease was observed on control plants. A fungus identical in culture morphology to R. solani AG-4 was consistently reisolated from symptomatic tissues, confirming its pathogenicity. To our knowledge, this is the first report in the world of R. solani causing damping-off on Mediterranean fan palm. References: (1) R. J. Bandoni. Mycologia 71:873, 1979. (2) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals Magnitude of thoracic spine deformity affecting morphologial characteristics of paraspinal muscles in patients with severe idiopathic scoliosis

2021 ◽  
Vol 27 (1) ◽  
pp. 68-73
Author(s):  
E.N. Shchurova ◽  
◽  
G.N. Filimonova ◽  
S.O. Ryabykh ◽  
◽  
...  
Keyword(s):  
Idiopathic Scoliosis ◽  
Thoracic Spine ◽  
Light Microscope ◽  
Structural Changes ◽  
Morphological Characteristics ◽  
Surgical Correction ◽  
Control Group ◽  
Special Focus ◽  
Spine Deformity ◽  
Paraspinal Muscles

Introduction Morphological, biochemical and histopathological characteristics of paraspinal muscles have been well described in patients with idiopathic scoliosis. However, there is a paucity of literature on morphological picture of paraspinal muscles in patients with severe idiopathic scoliosis. Objective To explore how the magnitude of thoracic spine deformity affects morphological characteristics of paraspinal muscles in patients with severe idiopathic scoliosis. Material and methods A total 21 patients with idiopathic scoliosis were reviewed. The patients were assigned to two groups depending on magnitude of preoperative thoracic spine deformity. A major group consisted of patients with scoliosis of ≥ 60º (n = 11) and control group included patients with a curve < 60º (n=10). Biopsy samples were taken from muscle fragments (multifidus muscle) at the apex of the curve (major arc) at the Th6-Th10 level on the convex side while approaching to the posterior spinal structures during surgical correction of kyphoscoliosis using light microscope. The specimens were examined histologically with light microscope. Results Patients with severe idiopathic scoliosis (≥ 60º) showed evident muscle fiber atrophy and dystrophy of different extent. There were nucleus free areas and homogenized muscle fragments observed with connective tissue layers being swollen and frayed with multiple fibroblasts seen in nearly all the samples. Arterial walls were normally fibrotized. Structural changes ranged from minimal with a curve of 60º to degrading muscles with the fibers replaced by fat and connective tissues with a curve angle of 145º. Conclusion Morphological characteristics of paraspinal muscles have been shown to be severely affected by the magnitude of thoracic spine deformity in patients with severe idiopathic scoliosis. The findings should be considered in surgical correction of kyphoscoliosis with special focus on postoperative vascular and neurotropic therapy to allow wound healing and lower complication rate.

scholarly journals First Report of Damping-Off Caused by Rhizoctonia solani AG-4 on Lagunaria patersonii in Italy

Plant Disease ◽  
2008 ◽  
Vol 92 (5) ◽  
pp. 836-836 ◽  
Author(s):  
D. Aiello ◽  
G. Parlavecchio ◽  
A. Vitale ◽  
E. Lahoz ◽  
R. Nicoletti ◽  
...  
Keyword(s):  
Rhizoctonia Solani ◽  
Morphological Characteristics ◽  
Ruthenium Red ◽  
Fluorescent Light ◽  
Damping Off ◽  
First Report ◽  
Pectic Enzymes ◽  
Electrophoretic Patterns ◽  
Blue Solution ◽  
Hyphal Diameter

Lagunaria patersonii (Adr.) G. Don (cow itch tree) is native to Australia and tolerates salted winds. During July 2007, damping-off of cow itch tree was observed on 4-month-old seedlings growing in a commercial nursery in eastern Sicily, Italy. More than 20% of the seedlings showed disease symptoms. First symptoms consisting of water-soaked lesions at the seedling base that expand rapidly girdle the stem and collapse the seedling in a few days. Diseased tissues were disinfested for 1 min in 1% NaOCl, rinsed in sterile water, plated on potato dextrose agar (PDA) amended with streptomycin sulphate at 100 mg/l, and then incubated at 25°C. A fungus with mycelial and morphological characteristics of Rhizoctonia solani Kühn was consistently yielded. Fungal colonies were initially white, turned brown with age, and produced irregularly shaped, brown sclerotia. Microscopic examination revealed that hyphae had a right-angle branching pattern, were constricted at the base of the branch near the union with main hyphae, and septate near the constriction. Basidia were not observed in the greenhouses or on the plates. Hyphal cells were determined to be multinucleate when stained with 0.5% aniline blue solution and examined at ×400 magnification with a microscope. Anastomosis groups were determined by pairing isolates on 2% water agar in petri plates (3). Pairings were made with tester strains of AG-1 IA, AG-2-2-1, AG-2-2IIIB, AG-2-2IV, AG-3, AG-4, AG-5, AG-6, AG-11. Anastomosis was observed only with tester isolates of AG-4 producing both C2 and C3 reactions. The hyphal diameter at the point of anastomosis was reduced, the anastomosis point was obvious, and cell death of adjacent cells was observed. These results were consistent with other reports on anastomosis reactions (1). The identification of group AG-4 within R. solani has been confirmed by electrophoretic patterns of pectic enzymes (polygalacturonases) in vertical pectin-acrylamide gel stained with ruthenium red (2). Pathogenicity tests were conducted on potted, healthy, 3-month-old seedlings of cow itch tree. Twenty plants were inoculated by placing plugs of PDA from 5-day-old mycelial cultures near the base of the stem. The same number of plants was treated with 1 cm2 PDA plugs as control. Plants were kept at 25°C and 95% relative humidity on a 12-h fluorescent light/dark regimen. Wilt symptoms due to basal stem rot, identical to ones observed in the nursery, appeared 10 days after inoculation and all inoculated plants showed symptoms within 1 month. Control plants remained healthy. The pathogen was reisolated from symptomatic tissues, completing Koch's postulates. To our knowledge, this is the first report in the world of R. solani causing disease on L. patersonii. References: (1) D. E. Carling. Page 37 in: Grouping in Rhizoctonia solani by Hyphal Anastomosis Reactions. Kluwer Academic Publishers, the Netherlands, 1996. (2) R. H. Cruickshank and G. C. Wade. Anal. Biochem. 107:177, 1980. (3) C. C. Tu and J. W. Kimbrough. Mycologia 65:941, 1973.

scholarly journals Zika virus replication in glioblastoma cells: electron microscopic tomography shows 3D arrangement of endoplasmic reticulum, replication organelles, and viral ribonucleoproteins

2021 ◽  
Author(s):  
Johannes Wieland ◽  
Stefan Frey ◽  
Ulrich Rupp ◽  
Sandra Essbauer ◽  
Rüdiger Groß ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Cell Line ◽  
Zika Virus ◽  
Structural Changes ◽  
Electron Tomography ◽  
Glioblastoma Cells ◽  
Electron Microscopic ◽  
N Protein ◽  
Ribonucleoprotein Complexes ◽  
Infected Cells

AbstractStructural changes of two patient-derived glioblastoma cell lines after Zika virus infection were investigated using scanning transmission electron tomography on high-pressure-frozen, freeze-substituted samples. In Zika-virus-infected cells, Golgi structures were barely visible under an electron microscope, and viral factories appeared. The cytosol outside of the viral factories resembled the cytosol of uninfected cells. The viral factories contained largely deranged endoplasmic reticulum (ER), filled with many so-called replication organelles consisting of a luminal vesicle surrounded by the ER membrane. Viral capsids were observed in the vicinity of the replication organelles (cell line #12537 GB) or in ER cisternae at large distance from the replication organelles (cell line #15747 GB). Near the replication organelles, we observed many about 100-nm-long filaments that may represent viral ribonucleoprotein complexes (RNPs), which consist of the RNA genome and N protein oligomers. In addition, we compared Zika-virus-infected cells with cells infected with a phlebovirus (sandfly fever Turkey virus). Zika virions are formed in the ER, whereas phlebovirus virions are assembled in the Golgi apparatus. Our findings will help to understand the replication cycle in the virus factories and the building of the replication organelles in glioblastoma cells.

scholarly journals Growth Phase Regulation of Vibrio cholerae RTX Toxin Export

2006 ◽  
Vol 189 (5) ◽  
pp. 1827-1835 ◽  
Author(s):  
Bethany Kay Boardman ◽  
Brian M. Meehan ◽  
Karla J. Fullner Satchell
Keyword(s):  
Stationary Phase ◽  
Vibrio Cholerae ◽  
Growth Phase ◽  
Diarrheal Disease ◽  
Outer Membrane Vesicles ◽  
Transcriptional Level ◽  
Type I ◽  
Bacterial Membranes ◽  
Rtx Toxin ◽  
Phase Regulation

ABSTRACT Vibrio cholerae, the causative agent of the severe diarrheal disease cholera, secretes several “accessory” toxins, including RTX toxin, which causes the cross-linking of the actin cytoskeleton. RTX toxin is exported to the extracellular milieu by an atypical type I secretion system (T1SS), and we previously noted that RTX-associated activity is detectable only in supernatant fluids from log phase cultures. Here, we investigate the mechanisms for regulating RTX toxin activity in supernatant fluids. We find that exported proteases are capable of destroying RTX activity and may therefore play a role in the growth phase regulation of toxin activity. We determined that the absence of RTX toxin in stationary-phase culture supernatant fluids is also due to a lack of toxin secretion and not attributable to solely proteolytic degradation. We ascertained that the T1SS apparatus is regulated at the transcriptional level by growth phase control that is independent of quorum sensing, unlike other virulence factors of V. cholerae. Additionally, in stationary-phase cultures, all RTX toxin activity is associated with bacterial membranes or outer membrane vesicles.

scholarly journals The Transcriptional Regulator VqmA Increases Expression of the Quorum-Sensing Activator HapR in Vibrio cholerae

2006 ◽  
Vol 188 (7) ◽  
pp. 2446-2453 ◽  
Author(s):  
Zhi Liu ◽  
Ansel Hsiao ◽  
Adam Joelsson ◽  
Jun Zhu
Keyword(s):  
Quorum Sensing ◽  
Vibrio Cholerae ◽  
Diarrheal Disease ◽  
Constitutive Expression ◽  
Physiological Role ◽  
Transcriptional Regulator ◽  
Protease Production ◽  
Dependent Manner ◽  
Cell Densities

ABSTRACT Vibrio cholerae is the causative agent of the severe diarrheal disease cholera. A number of environmental stimuli regulate virulence gene expression in V. cholerae, including quorum-sensing signals. At high cell densities, quorum sensing in V. cholerae invokes a series of signal transduction pathways in order to activate the expression of the master regulator HapR, which then represses the virulence regulon and biofilm-related genes and activates protease production. In this study, we identified a transcriptional regulator, VqmA (VCA1078), that activates hapR expression at low cell densities. Under in vitro inducing conditions, constitutive expression of VqmA represses the virulence regulon in a HapR-dependent manner. VqmA increases hapR transcription as measured by the activity of the hapR-lacZ reporter, and it increases HapR production as measured by Western blotting. Using a heterogenous luxCDABE cosmid, we found that VqmA stimulates quorum-sensing regulation at lower cell densities and that this stimulation bypasses the known LuxO-small-RNA regulatory circuits. Furthermore, we showed that VqmA regulates hapR transcription directly by binding to its promoter region and that expression of vqmA is cell density dependent and autoregulated. The physiological role of VqmA is also discussed.

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