scholarly journals Ras Proteins Have Multiple Functions in Vegetative Cells of Dictyostelium

2010 ◽  
Vol 9 (11) ◽  
pp. 1728-1733 ◽  
Author(s):  
Parvin Bolourani ◽  
George Spiegelman ◽  
Gerald Weeks
Keyword(s):  
Cyclic Amp ◽  
Vegetative Cell ◽  
Ras Proteins ◽  
Random Motility ◽  
Vegetative Cells ◽  
Content Type ◽  
Multiple Functions ◽  
Mutant Cells

ABSTRACT During the aggregation of Dictyostelium cells, signaling through RasG is more important in regulating cyclic AMP (cAMP) chemotaxis, whereas signaling through RasC is more important in regulating the cAMP relay. However, RasC is capable of substituting for RasG for chemotaxis, since rasG − cells are only partially deficient in chemotaxis, whereas rasC −/rasG − cells are totally incapable of chemotaxis. In this study we have examined the possible functional overlap between RasG and RasC in vegetative cells by comparing the vegetative cell properties of rasG −, rasC −, and rasC −/rasG − cells. In addition, since RasD, a protein not normally found in vegetative cells, is expressed in vegetative rasG − and rasC −/rasG − cells and appears to partially compensate for the absence of RasG, we have also examined the possible functional overlap between RasG and RasD by comparing the properties of rasG − and rasC −/rasG − cells with those of the mutant cells expressing higher levels of RasD. The results of these two lines of investigation show that RasD is capable of totally substituting for RasG for cytokinesis and growth in suspension, whereas RasC is without effect. In contrast, for chemotaxis to folate, RasC is capable of partially substituting for RasG, but RasD is totally without effect. Finally, neither RasC nor RasD is able to substitute for the role that RasG plays in regulating actin distribution and random motility. These specificity studies therefore delineate three distinct and none-overlapping functions for RasG in vegetative cells.

scholarly journals An Adenylyl Cyclase, CyaB, Acts as an Osmosensor in Myxococcus xanthus

2005 ◽  
Vol 187 (10) ◽  
pp. 3593-3598 ◽  
Author(s):  
Yoshio Kimura ◽  
Mika Ohtani ◽  
Kaoru Takegawa
Keyword(s):  
Cyclic Amp ◽  
Adenylyl Cyclase ◽  
Growth Retardation ◽  
Spore Germination ◽  
Germination Rate ◽  
Myxococcus Xanthus ◽  
Receptor Type ◽  
Wild Type ◽  
Vegetative Cells ◽  
Mutant Cells

ABSTRACT We have previously reported that a receptor-type adenylyl cyclase (CyaA) of Myxococcus xanthus undergoes an osmosensor mainly during spore germination (Y. Kimura et al., J. Bacteriol. 184:3578-3585, 2002). In the present study, we cloned another receptor-type adenylyl cyclase gene (cyaB) and characterized the function of the cyaB-encoded protein. Disruption of cyaB generates a mutant that showed growth retardation at high ionic (NaCl) or high nonionic (sucrose) osmolarity. When vegetative cells were stimulated with 0.15 M NaCl, the increases in intracellular cyclic AMP levels of cyaB mutant cells were lower than those of wild-type cells. Under nonionic osmostress, the cyaB mutant exhibited reduced spore germination; however, the germination rate of the cyaB mutant was significantly higher than that of the cyaA mutant.

scholarly journals Differentiation of Vegetative Cells into Spores: a Kinetic Model Applied toBacillus subtilis

2019 ◽  
Vol 85 (10) ◽  
Author(s):  
Emilie Gauvry ◽  
Anne-Gabrielle Mathot ◽  
Olivier Couvert ◽  
Ivan Leguérinel ◽  
Matthieu Jules ◽  
...  
Keyword(s):  
Bacillus Subtilis ◽  
Vegetative Cell ◽  
Goodness Of Fit ◽  
Fluorescent Protein ◽  
Raw Materials ◽  
Spore Formation ◽  
Vegetative Cells ◽  
Content Type ◽  
Kinetics Of ◽  
Over Time

ABSTRACTSpore-forming bacteria are natural contaminants of food raw materials, and sporulation can occur in many environments from farm to fork. In order to characterize and to predict spore formation over time, we developed a model that describes both the kinetics of growth and the differentiation of vegetative cells into spores. The model is based on a classical growth model and enables description of the kinetics of sporulation with the addition of three parameters specific to sporulation. Two parameters are related to the probability of each vegetative cell to commit to sporulation and to form a spore, and the last one is related to the time needed to form a spore once the cell is committed to sporulation. The goodness of fit of this growth-sporulation model was assessed using growth-sporulation kinetics at various temperatures in laboratory medium or in whey forBacillus subtilis,Bacillus cereus, andBacillus licheniformis. The model accurately describes the kinetics in these different conditions, with a mean error lower than 0.78 log10CFU/ml for the growth and 1.08 log10CFU/ml for the sporulation. The biological meaning of the parameters was validated with a derivative strain ofBacillus subtilis168 which produces green fluorescent protein at the initiation of sporulation. This model provides physiological information on the spore formation and on the temporal abilities of vegetative cells to differentiate into spores and reveals the heterogeneity of spore formation during and after growth.IMPORTANCEThe growth-sporulation model describes the progressive transition from vegetative cells to spores with sporulation parameters describing the sporulation potential of each vegetative cell. Consequently, the model constitutes an interesting tool to assess the sporulation potential of a bacterial population over time with accurate parameters such as the time needed to obtain one resistant spore and the probability of sporulation. Further, this model can be used to assess these data under various environmental conditions in order to better identify the conditions favorable for sporulation regarding the time to obtain the first spore and/or the concentrations of spores which could be reached during a food process.

scholarly journals Activity of Hospital Disinfectants against Vegetative Cells and Spores of Clostridioides difficile Embedded in Biofilms

2019 ◽  
Vol 64 (1) ◽  
Author(s):  
Tasnuva Rashid ◽  
Farnoosh Haghighi ◽  
Irtiza Hasan ◽  
Eugénie Bassères ◽  
M. Jahangir Alam ◽  
...  
Keyword(s):  
Cell Growth ◽  
Vegetative Cell ◽  
Growth Time ◽  
Future Research ◽  
Primary Analysis ◽  
Vegetative Cells ◽  
Biofilm Growth ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile spores can survive in the environment in either mono- or mixed-species biofilms. However, no previous studies have investigated chemical disinfection of C. difficile spores embedded in biofilms. Thus, the purpose of this study was to assess the in vitro effectiveness of hospital disinfectants against C. difficile spores embedded within biofilms. Five unique C. difficile strains embedded in three different biofilm types grown for 72 or 120 h were exposed to seven different hospital disinfectants. C. difficile abundance [as log(number of CFU/milliliter)] was calculated after manufacturer-determined contact times along with biofilm biomass and microscopy. The primary analysis compared differences between C. difficile vegetative cell and spore counts as well as amounts of biomass after exposure to disinfectants. C. difficile vegetative cells and spores were recovered from biofilms regardless of the type of biofilm growth or biofilm growth time. No disinfectant was able to completely eliminate C. difficile from the biofilms. Overall, Clorox, ortho-phthalaldehyde (OPA), and Virex were most effective at killing C. difficile spores regardless of biofilm age, ribotype, or wash conditions (whether biofilms are washed or unwashed) (P = 0.001, each). Clorox and OPA were also effective at killing total vegetative cell growth (P = 0.001, each), but Virex was found to be ineffective against vegetative cell growth in biofilms (P = 0.77). Clorox and Virex were most effective in reducing biomass, followed by Nixall, OPA, and Vital Oxide. No disinfectant was able to completely eliminate C. difficile embedded within biofilms although differences among disinfectants were noted. Future research will be required to determine methods to eradicate this persister reservoir.

scholarly journals The Putative Eukaryote-LikeO-GlcNAc Transferase of the Cyanobacterium Synechococcus elongatus PCC 7942 Hydrolyzes UDP-GlcNAc and Is Involved in Multiple Cellular Processes

2014 ◽  
Vol 197 (2) ◽  
pp. 354-361 ◽  
Author(s):  
Kerry A. Sokol ◽  
Neil E. Olszewski
Keyword(s):  
Deletion Mutant ◽  
Bacterial Species ◽  
Synechococcus Elongatus ◽  
Single Amino Acid ◽  
Content Type ◽  
Cellular Processes ◽  
Mutant Phenotypes ◽  
Glcnac Transferase ◽  
Pcc 7942 ◽  
Mutant Cells

The posttranslational addition of a single O-linked β-N-acetylglucosamine (O-GlcNAc) to serine or threonine residues regulates numerous metazoan cellular processes. The enzyme responsible for this modification,O-GlcNAc transferase (OGT), is conserved among a wide variety of organisms and is critical for the viability of many eukaryotes. Although OGTs with domain structures similar to those of eukaryotic OGTs are predicted for many bacterial species, the cellular roles of these OGTs are unknown. We have identified a putative OGT in the cyanobacteriumSynechococcus elongatusPCC 7942 that shows active-site homology and similar domain structure to eukaryotic OGTs. An OGT deletion mutant was created and found to exhibit several phenotypes. Without agitation, mutant cells aggregate and settle out of the medium. The mutant cells have higher free inorganic phosphate levels, wider thylakoid lumen, and differential accumulation of electron-dense inclusion bodies. These phenotypes are rescued by reintroduction of the wild-type OGT but are not fully rescued by OGTs with single amino acid substitutions corresponding to mutations that reduce eukaryotic OGT activity.S. elongatusOGT purified fromEscherichia colihydrolyzed the sugar donor, UDP-GlcNAc, while the mutant OGTs that did not fully rescue the deletion mutant phenotypes had reduced or no activity. These results suggest that bacterial eukaryote-like OGTs, like their eukaryotic counterparts, influence multiple processes.

scholarly journals Coxiella burnetii Alters Cyclic AMP-Dependent Protein Kinase Signaling during Growth in Macrophages

2012 ◽  
Vol 80 (6) ◽  
pp. 1980-1986 ◽  
Author(s):  
Laura J. MacDonald ◽  
Richard C. Kurten ◽  
Daniel E. Voth
Keyword(s):  
Protein Kinase ◽  
Cyclic Amp ◽  
Coxiella Burnetii ◽  
Alveolar Macrophages ◽  
Q Fever ◽  
Parasitophorous Vacuole ◽  
Dependent Protein Kinase ◽  
Content Type ◽  
Bacterial Agent ◽  
Dependent Protein

ABSTRACTCoxiella burnetiiis the bacterial agent of human Q fever, an acute, flu-like illness that can present as chronic endocarditis in immunocompromised individuals. Following aerosol-mediated transmission,C. burnetiireplicates in alveolar macrophages in a unique phagolysosome-like parasitophorous vacuole (PV) required for survival. The mechanisms ofC. burnetiiintracellular survival are poorly defined and a recent Q fever outbreak in the Netherlands emphasizes the need for better understanding this unique host-pathogen interaction. We recently demonstrated that inhibition of host cyclic AMP-dependent protein kinase (PKA) activity negatively impacts PV formation. In the current study, we confirmed PKA involvement in PV biogenesis and probed the role of PKA signaling duringC. burnetiiinfection of macrophages. Using PKA-specific inhibitors, we found the kinase was needed for biogenesis of prototypical PV andC. burnetiireplication. PKA and downstream targets were differentially phosphorylated throughout infection, suggesting prolonged regulation of the pathway. Importantly, the pathogen actively triggered PKA activation, which was also required for PV formation by virulentC. burnetiiisolates during infection of primary human alveolar macrophages. A subset of PKA-specific substrates were differentially phosphorylated duringC. burnetiiinfection, suggesting the pathogen uses PKA signaling to control distinct host cell responses. Collectively, the current results suggest a versatile role for PKA inC. burnetiiinfection and indicate virulent organisms usurp host kinase cascades for efficient intracellular growth.

scholarly journals The Cyclic AMP Receptor Protein Regulates Quorum Sensing and Global Gene Expression in Yersinia pestis during Planktonic Growth and Growth in Biofilms

mBio ◽  
2019 ◽  
Vol 10 (6) ◽  
Author(s):  
Jeremy T. Ritzert ◽  
George Minasov ◽  
Ryan Embry ◽  
Matthew J. Schipma ◽  
Karla J. F. Satchell
Keyword(s):  
Gene Expression ◽  
Quorum Sensing ◽  
Carbon Source ◽  
Cyclic Amp ◽  
Yersinia Pestis ◽  
Carbon Sources ◽  
Transcriptional Regulator ◽  
Receptor Protein ◽  
Content Type ◽  
Bacterial Physiology

ABSTRACT Cyclic AMP (cAMP) receptor protein (Crp) is an important transcriptional regulator of Yersinia pestis. Expression of crp increases during pneumonic plague as the pathogen depletes glucose and forms large biofilms within lungs. To better understand control of Y. pestis Crp, we determined a 1.8-Å crystal structure of the protein-cAMP complex. We found that compared to Escherichia coli Crp, C helix amino acid substitutions in Y. pestis Crp did not impact the cAMP dependency of Crp to bind DNA promoters. To investigate Y. pestis Crp-regulated genes during plague pneumonia, we performed RNA sequencing on both wild-type and Δcrp mutant bacteria growing in planktonic and biofilm states in minimal media with glucose or glycerol. Y. pestis Crp was found to dramatically alter expression of hundreds of genes in a manner dependent upon carbon source and growth state. Gel shift assays confirmed direct regulation of the malT and ptsG promoters, and Crp was then linked to Y. pestis growth on maltose as a sole carbon source. Iron regulation genes ybtA and fyuA were found to be indirectly regulated by Crp. A new connection between carbon source and quorum sensing was revealed as Crp was found to regulate production of acyl-homoserine lactones (AHLs) through direct and indirect regulation of genes for AHL synthetases and receptors. AHLs were subsequently identified in the lungs of Y. pestis-infected mice when crp expression was highest in Y. pestis biofilms. Thus, in addition to the well-studied pla gene, other Crp-regulated genes likely have important functions during plague infection. IMPORTANCE Bacterial pathogens have evolved extensive signaling pathways to translate environmental signals into changes in gene expression. While Crp has long been appreciated for its role in regulating metabolism of carbon sources in many bacterial species, transcriptional profiling has revealed that this protein regulates many other aspects of bacterial physiology. The plague pathogen Y. pestis requires this global regulator to survive in blood, skin, and lungs. During disease progression, this organism adapts to changes within these niches. In addition to regulating genes for metabolism of nonglucose sugars, we found that Crp regulates genes for virulence, metal acquisition, and quorum sensing by direct or indirect mechanisms. Thus, this single transcriptional regulator, which responds to changes in available carbon sources, can regulate multiple critical behaviors for causing disease.

scholarly journals Activation of an Essential Calcium Signaling Pathway in Saccharomyces cerevisiae by Kch1 and Kch2, Putative Low-Affinity Potassium Transporters

2012 ◽  
Vol 12 (2) ◽  
pp. 204-214 ◽  
Author(s):  
Christopher P. Stefan ◽  
Nannan Zhang ◽  
Takaaki Sokabe ◽  
Alberto Rivetta ◽  
Clifford L. Slayman ◽  
...  
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Animal Cell ◽  
Cell Types ◽  
Activation Mechanism ◽  
Homologous Pair ◽  
Content Type ◽  
Mating Pheromones ◽  
Inwardly Rectifying ◽  
Low K ◽  
Mutant Cells

ABSTRACT In the budding yeast Saccharomyces cerevisiae , mating pheromones activate a high-affinity Ca 2+ influx system (HACS) that activates calcineurin and is essential for cell survival. Here we identify extracellular K + and a homologous pair of transmembrane proteins, Kch1 and Kch2 (Prm6), as necessary components of the HACS activation mechanism. Expression of Kch1 and especially Kch2 was strongly induced during the response to mating pheromones. When forcibly overexpressed, Kch1 and Kch2 localized to the plasma membrane and activated HACS in a fashion that depended on extracellular K + but not pheromones. They also promoted growth of trk1 trk2 mutant cells in low K + environments, suggesting they promote K + uptake. Voltage-clamp recordings of protoplasts revealed diminished inward K + currents in kch1 kch2 double-mutant cells relative to the wild type. Conversely, heterologous expression of Kch1 in HEK293T cells caused the appearance of inwardly rectifying K + currents. Collectively, these findings suggest that Kch1 and Kch2 directly promote K + influx and that HACS may electrochemically respond to K + influx in much the same way as the homologous voltage-gated Ca 2+ channels in most animal cell types.

Basal Body and Flagellar Development During the Vegetative Cell Cycle and the Sexual Cycle of Chlamydomonas Reinhardii

1974 ◽  
Vol 16 (3) ◽  
pp. 529-556 ◽  
Author(s):  
T. CAVALIER-SMITH
Keyword(s):  
Basal Body ◽  
Vegetative Cell ◽  
Amorphous Material ◽  
Sexual Cycle ◽  
Transitional Region ◽  
Basal Bodies ◽  
Vegetative Cells ◽  
Chlamydomonas Reinhardii ◽  
Body Development ◽  
Microtubular Roots

Basal body development and flagellar regression and growth in the unicellular green alga Chlamydomonas reinhardii were studied by light and electron microscopy during the vegetative cell cycle in synchronous cultures and during the sexual life cycle. Flagella regress by gradual shortening prior to vegetative cell division and also a few hours after cell fusion in the sexual cycle. In vegetative cells basal bodies remain attached to the plasma membrane by their transitional fibres and do not act as centrioles at the spindle poles during division. In zygotes the basal bodies and associated microtubular roots and cross-striated connexions all dissolve, and by 6.5 h after mating all traces of flagellar apparatus and associated structures have disappeared. They remain absent for 6 days throughout zygospore maturation and then are reassembled during zygospore germination, after meiosis has begun. Basal body assembly in developing zygospores occurs close to the plasma membrane (in the absence of pre-existing basal bodies) via an intermediate stage consisting of nine single A-tubules surrounding a central ‘cartwheel’. Assembly is similar in vegetative cells (and occurs prior to cell division), except that new basal bodies are physically attached to old ones by amorphous material. In vegetative cells, amorphous disks, which may possibly be still earlier stages in basal-body development occur in the same location as 9-singlet developing basal bodies. After the 9-singlet structure is formed, B and C fibres are added and the basal body elongates to its mature length. Microtubular roots, striated connexions and flagella are then assembled. Both flagellar regression and growth are gradual and sequential, the transitional region at the base of the flagellum being formed first and broken down last. The presence of amorphous material at the tip of the axoneme of growing and regressing flagella suggests that the axoneme grows or shortens by the sequential assembly or disassembly at its tip. In homogenized cells basal bodies remain firmly attached to each other by their striated connexions. The flagellar transitional region, and parts of the membrane and of the 4 microtubular roots, also remain attached; so also do new developing basal bodies, if present. These structures are well preserved in homogenates and new fine-structural details can be seen. These results are discussed, and lend no support to the idea that basal bodies have genetic continuity. It is suggested that basal body development can be best understood if a distinction is made between the information needed to specify the structure of a basal body and that needed to specify its location and orientation.

Actin During Pollen Germination

1986 ◽  
Vol 86 (1) ◽  
pp. 1-8
Author(s):  
J. HESLOP-HARRISON ◽  
Y. HESLOP-HARRISON ◽  
M. CRESTI ◽  
A. TIEZZI ◽  
F. CIAMPOLINI
Keyword(s):  
Medium Release ◽  
Pollen Tube ◽  
Vegetative Cell ◽  
Pollen Germination ◽  
Pollen Grain ◽  
Actin Microfilaments ◽  
Vegetative Cells ◽  
Stage Of Development ◽  
Angiosperm Species

The cytoplasm of the vegetative cell of the ungerminated pollen grain of Endymton non-scriplus and other angiosperm species contains numerous fusiform bodies sometimes exceeding 15μm in length and 2.5 μm in width, which bind fluorescent-labelled phalloidin and are likely therefore to constitute a storage form of actin. The bodies are dispersed during the activation of the pollen, being replaced by aggregates of slender phalloidin-binding fibrils, which converge towards the germination apertures and are present in the emerging pollen tube. The storage bodies appear to be homologous with crystalline-fibrillar structures, shown in an earlier paper to be abundantly present in the vegetative cells of Nicotiana pollen. These are composed of massive aggregates of linearly disposed units with individual widths of 4–7 nm, probably to be interpreted as actin microfilaments. Vegetative-cell protoplasts from mature but ungerminated pollen disrupted in osmotically balancing medium release extended phalloidin-binding fibrils of a kind not observed in the intact grain. It is suggested that these are derived by the rapid dissociation of the compact actin storage bodies present in the vegetative cell at this stage of development.

scholarly journals How the Anaerobic Enteropathogen Clostridioides difficile Tolerates Low O2 Tensions

mBio ◽  
2020 ◽  
Vol 11 (5) ◽  
Author(s):  
Nicolas Kint ◽  
Carolina Alves Feliciano ◽  
Maria C. Martins ◽  
Claire Morvan ◽  
Susana F. Fernandes ◽  
...  
Keyword(s):  
Gastrointestinal Tract ◽  
Anaerobic Bacteria ◽  
Growth Defect ◽  
Strictly Anaerobic ◽  
Low Oxygen ◽  
Air Exposure ◽  
Vegetative Cells ◽  
Content Type ◽  
Clostridioides Difficile

ABSTRACT Clostridioides difficile is a major cause of diarrhea associated with antibiotherapy. After germination of C. difficile spores in the small intestine, vegetative cells are exposed to low oxygen (O2) tensions. While considered strictly anaerobic, C. difficile is able to grow in nonstrict anaerobic conditions (1 to 3% O2) and tolerates brief air exposure indicating that this bacterium harbors an arsenal of proteins involved in O2 detoxification and/or protection. Tolerance of C. difficile to low O2 tensions requires the presence of the alternative sigma factor, σB, involved in the general stress response. Among the genes positively controlled by σB, four encode proteins likely involved in O2 detoxification: two flavodiiron proteins (FdpA and FdpF) and two reverse rubrerythrins (revRbr1 and revRbr2). As previously observed for FdpF, we showed that both purified revRbr1 and revRbr2 harbor NADH-linked O2- and H2O2-reductase activities in vitro, while purified FdpA mainly acts as an O2-reductase. The growth of a fdpA mutant is affected at 0.4% O2, while inactivation of both revRbrs leads to a growth defect above 0.1% O2. O2-reductase activities of these different proteins are additive since the quadruple mutant displays a stronger phenotype when exposed to low O2 tensions compared to the triple mutants. Our results demonstrate a key role for revRbrs, FdpF, and FdpA proteins in the ability of C. difficile to grow in the presence of physiological O2 tensions such as those encountered in the colon. IMPORTANCE Although the gastrointestinal tract is regarded as mainly anoxic, low O2 tension is present in the gut and tends to increase following antibiotic-induced disruption of the host microbiota. Two decreasing O2 gradients are observed, a longitudinal one from the small to the large intestine and a second one from the intestinal epithelium toward the colon lumen. Thus, O2 concentration fluctuations within the gastrointestinal tract are a challenge for anaerobic bacteria such as C. difficile. This enteropathogen has developed efficient strategies to detoxify O2. In this work, we identified reverse rubrerythrins and flavodiiron proteins as key actors for O2 tolerance in C. difficile. These enzymes are responsible for the reduction of O2 protecting C. difficile vegetative cells from associated damages. Original and complex detoxification pathways involving O2-reductases are crucial in the ability of C. difficile to tolerate O2 and survive to O2 concentrations encountered in the gastrointestinal tract.

Sign in / Sign up

Export Citation Format

Share Document