scholarly journals Non-canonical localization of RubisCO under high light conditions in the toxic cyanobacteriumMicrocystis aeruginosaPCC7806

2019 ◽  
Author(s):  
Tino Barchewitz ◽  
Arthur Guljamow ◽  
Sven Meissner ◽  
Stefan Timm ◽  
Manja Henneberg ◽  
...  
Keyword(s):  
Subcellular Localization ◽  
Cytoplasmic Membrane ◽  
High Cell Density ◽  
High Light ◽  
Membrane Association ◽  
High Cell ◽  
Light Conditions ◽  
Wild Type ◽  
Electron Microscopic ◽  
Steady State Levels

AbstractThe frequent production of the hepatotoxin microcystin and its impact on the life-style of bloom-forming cyanobacteria are poorly understood. Here we report that microcystin interferes with the assembly and the subcellular localization of RubisCO, inMicrocystis aeruginosaPCC7806. Immunofluorescence, electron microscopic and cellular fractionation studies revealed a pronounced heterogeneity in the subcellular localization of RubisCO. At high cell density, RubisCO particles are largely separate from carboxysomes inM. aeruginosaand relocate to the cytoplasmic membrane under high-light conditions. We hypothesize that the binding of microcystin to RubisCO promotes its membrane association and enables an extreme versatility of the enzyme. Steady-state levels of the RubisCO CO2fixation product 3-phosphoglycerate are significantly higher in the microcystin-producing wild type. We also detected noticeable amounts of the RubisCO oxygenase reaction product secreted into the medium that may support the mutual interaction ofM. aeruginosawith its heterotrophic microbial community.

Stomatal aperture can compensate altered stomatal density in Arabidopsis thaliana at growth light conditions

2006 ◽  
Vol 33 (11) ◽  
pp. 1037 ◽  
Author(s):  
Dirk Büssis ◽  
Uritza von Groll ◽  
Joachim Fisahn ◽  
Thomas Altmann
Keyword(s):  
Arabidopsis Thaliana ◽  
Stomatal Conductance ◽  
Stomatal Density ◽  
Co2 Assimilation ◽  
High Light ◽  
Stomatal Aperture ◽  
Photochemical Quenching ◽  
Light Conditions ◽  
Wild Type ◽  
Light Intensities

Stomatal density of transgenic Arabidopsis thaliana plants over-expressing the SDD1 (stomatal density and distribution) gene was reduced to 40% and in the sdd1-1 mutant increased to 300% of the wild type. CO2 assimilation rate and stomatal conductance of over-expressers and the sdd1-1 mutant were unchanged compared with wild types when measured under the light conditions the plants were exposed to during growth. Lower stomatal density was compensated for by increased stomatal aperture and conversely, increased stomatal density was compensated for by reduced stomatal aperture. At high light intensities the assimilation rates and stomatal conductance of SDD1 over-expressers were reduced to 80% of those in wild type plants. Areas beneath stomata and patches lacking stomata were analysed separately. In areas without stomata, maximum fluorescence yield (Fv / Fm) and quantum yield of photosystem II (Φ PSII) were significantly lower than in areas beneath stomata. In areas beneath stomata, Fv / Fm and Φ PSII were identical to levels measured in wild type leaves. At high light intensities over-expressers showed decreased photochemical quenching (qP) compared with wild types. However, the decrease of qP was significantly stronger in areas without stomata than in mesophyll areas beneath stomata. At high CO2 partial pressures and high light intensities CO2 assimilation rates of SDD1 over-expressers did not reach wild type levels. These results indicate that photosynthesis in SDD1 over-expressers was reduced because of limiting CO2 in areas furthest from stomata at high light.

Murein components rescue developmental sporulation of Myxococcus xanthus

1982 ◽  
Vol 152 (1) ◽  
pp. 462-470 ◽  
Author(s):  
L J Shimkets ◽  
D Kaiser
Keyword(s):  
Fruiting Body ◽  
High Cell Density ◽  
Myxococcus Xanthus ◽  
Sodium Dodecyl ◽  
Protein Composition ◽  
Diaminopimelic Acid ◽  
Nutrient Level ◽  
High Cell ◽  
Wild Type ◽  
Nutrient Rich Medium

Murein (peptidoglycan) components are able to rescue sporulation in certain sporulation-defective mutants of Myxococcus xanthus. N-Acetylglucosamine, N-acetylmuramic acid, diaminopimelic acid, and D-alanine each increase the number of spores produced by SpoC mutants. When all four components are included they have a synergistic effect, raising the number of spores produced by SpoC mutants to the wild-type level. Murein-rescued spores are resistant to heat and sonic oscillation and germinate when plated on a nutrient-rich medium. They appear to be identical to fruiting body spores in their ultrastructure, in their protein composition, and in their resistance to boiling sodium dodecyl sulfate. Murein rescue of sporulation, like fruiting body sporulation, requires high cell density, a low nutrient level, and a solid surface.

scholarly journals Single Cells Exhibit Differing Behavioral Phases during Early Stages of Pseudomonas aeruginosa Swarming

2019 ◽  
Vol 201 (19) ◽  
Author(s):  
Chinedu S. Madukoma ◽  
Peixian Liang ◽  
Aleksandar Dimkovikj ◽  
Jianxu Chen ◽  
Shaun W. Lee ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Cell Motility ◽  
Single Cell ◽  
High Cell Density ◽  
Single Cells ◽  
High Cell ◽  
Wild Type ◽  
Content Type ◽  
Type Iv ◽  
The Many

ABSTRACT Pseudomonas aeruginosa is among the many bacteria that swarm, where groups of cells coordinate to move over surfaces. It has been challenging to determine the behavior of single cells within these high-cell-density swarms. To track individual cells within P. aeruginosa swarms, we imaged a fluorescently labeled subset of the larger population. Single cells at the advancing swarm edge varied in their motility dynamics as a function of time. From these data, we delineated four phases of early swarming prior to the formation of the tendril fractals characteristic of P. aeruginosa swarming by collectively considering both micro- and macroscale data. We determined that the period of greatest single-cell motility does not coincide with the period of greatest collective swarm expansion. We also noted that flagellar, rhamnolipid, and type IV pilus motility mutants exhibit substantially less single-cell motility than the wild type. IMPORTANCE Numerous bacteria exhibit coordinated swarming motion over surfaces. It is often challenging to assess the behavior of single cells within swarming communities due to the limitations of identifying, tracking, and analyzing the traits of swarming cells over time. Here, we show that the behavior of Pseudomonas aeruginosa swarming cells can vary substantially in the earliest phases of swarming. This is important to establish that dynamic behaviors should not be assumed to be constant over long periods when predicting and simulating the actions of swarming bacteria.

scholarly journals Activation of the Proprotein Transcription Factor Pro-ςE Is Associated with Its Progression through Three Patterns of Subcellular Localization during Sporulation in Bacillus subtilis

1998 ◽  
Vol 180 (9) ◽  
pp. 2426-2433 ◽  
Author(s):  
Antje Hofmeister
Keyword(s):  
Transcription Factor ◽  
Bacillus Subtilis ◽  
Subcellular Localization ◽  
Cytoplasmic Membrane ◽  
Immunofluorescence Microscopy ◽  
Active Form ◽  
Signal Transduction Pathway ◽  
Subcellular Fractionation ◽  
Membrane Association ◽  
Chemical Cross Linking

ABSTRACT The activity of the sporulation transcription factor ςE in Bacillus subtilis is governed by an intercellular signal transduction pathway that controls the conversion of the inactive proprotein pro-ςE to the mature and active form of the factor. Here I use immunofluorescence microscopy to show that the activation of the proprotein is associated with its progression through three patterns of subcellular localization. In the predivisional sporangium, pro-ςE was found to be associated with the cytoplasmic membrane. Next, at the stage of asymmetric division, pro-ςE accumulated at the sporulation septum. Finally, after processing, mature ςEwas found to be distributed throughout the mother cell cytoplasm. The results of subcellular fractionation and sedimentation in density gradients of extracts prepared from postdivisional sporangia confirmed that pro-ςE was chiefly present in the membrane fraction and that ςE was predominantly cytoplasmic, findings that suggest that the pro-amino acid sequence is responsible for the sequestration of pro-ςE to the membrane. The results of chemical cross-linking experiments showed that pro-ςE was present in a complex with its putative processing protein, SpoIIGA, or with a protein that depended on SpoIIGA. The membrane association of pro-ςE was, however, independent of SpoIIGA and other proteins specific to B. subtilis. Likewise, accumulation of pro-ςE at the septum did not depend on its interaction with SpoIIGA. Sequestration of pro-ςE to the membrane might serve to facilitate its interaction with SpoIIGA and may be important for preventing its premature association with core RNA polymerase. The implications of these findings for the compartmentalization of ςE are discussed.

scholarly journals Physiological and anatomical differentiation of two sympatric weed populations

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9226
Author(s):  
Barbara Neuffer ◽  
Michael Schorsch ◽  
Steffen Hameister ◽  
Johannes Knuesting ◽  
Jennifer Selinski ◽  
...  
Keyword(s):  
Photosynthetic Capacity ◽  
Common Type ◽  
High Light ◽  
Light Conditions ◽  
Wild Type ◽  
Low Light ◽  
Abaxial Epidermis ◽  
Different Types ◽  
The Common ◽  
Physiological Characters

In the vineyards of Rhineland-Palatinate (Germany), two different types of Shepherd’s Purse (Capsella bursa-pastoris) coexist: (1) the common type called ‘wild type’, and (2) the decandric type called Capsella apetala or ‘Spe’ with four stamens in place of the four petals. In this study, we compare the anatomical and physiological characters of rosette leaves of the respective types. Progeny of individual plants was cultivated in growth chambers under low- and high-light conditions. Under low-light conditions, the stomata densities of the adaxial and abaxial epidermis did not differ between the two types. When grown under high-light conditions, wild type and Spe, both exhibited increased stomata densities compared to low-light conditions, but Spe to a lesser extent than the wild type. The maximal photosynthetic capacity of Spe was lower in both, low-light and high-light conditions compared to wild-type plants. Under all CO2 concentrations, Spe seemed to be less productive. The less effective CO2 assimilation of the Spe mutant C. apetala was accompanied by later flowering. This fact prolonged the vegetative phase of Spe by about two weeks and was sufficient for the maintenance of both populations stably over years.

scholarly journals Structure-Function Study of MalF Protein by Random Mutagenesis

1999 ◽  
Vol 181 (7) ◽  
pp. 2267-2272 ◽  
Author(s):  
María Isabel Tapia ◽  
Michaël Mourez ◽  
Maurice Hofnung ◽  
Elie Dassa
Keyword(s):  
Steady State ◽  
Subcellular Localization ◽  
Cytoplasmic Membrane ◽  
Random Mutagenesis ◽  
State Level ◽  
Mutant Proteins ◽  
Transmembrane Segments ◽  
Functional Regions ◽  
Large N ◽  
Steady State Levels

ABSTRACT MalF is one of the two integral inner membrane proteins of the maltose-maltodextrin transport system. To identify functional regions in this protein, we characterized a collection of malFmutants obtained by random mutagenesis. We analyzed their growth on maltose and maltodextrins, the steady-state levels and subcellular localization of the mutant proteins, and the subcellular localization of MalK. Only 2 of the 21 MalF mutant proteins allowed growth on maltose and maltodextrins. Most mutations resulting in immunodetectable proteins mapped to hydrophilic domains, indicating that insertions affecting transmembrane segments gave rise to unstable or lethal proteins. All MalF mutant proteins, even those C-terminally truncated or with large N-terminal deletions, were inserted into the cytoplasmic membrane. Having identified mutations leading to reduced steady-state level, to partial mislocation, and/or to misfolding, we were able to assign to some regions of MalF a role in the assembly of the MalFGK2 complex and/or in the transport mechanism.

scholarly journals Reduced Levels of ATF-2 Predispose Mice to Mammary Tumors

2006 ◽  
Vol 27 (5) ◽  
pp. 1730-1744 ◽  
Author(s):  
Toshio Maekawa ◽  
Toshie Shinagawa ◽  
Yuji Sano ◽  
Takahiko Sakuma ◽  
Shintaro Nomura ◽  
...  
Keyword(s):  
Cell Density ◽  
Target Genes ◽  
High Cell Density ◽  
Critical Role ◽  
Susceptibility Gene ◽  
Mammary Tumors ◽  
Mrna Levels ◽  
High Cell ◽  
Wild Type ◽  
Induced Apoptosis

ABSTRACT Transcription factor ATF-2 is a nuclear target of stress-activated protein kinases, such as p38, which are activated by various extracellular stresses, including UV light. Here, we show that ATF-2 plays a critical role in hypoxia- and high-cell-density-induced apoptosis and the development of mammary tumors. Compared to wild-type cells, Atf-2 −/− mouse embryonic fibroblasts (MEFs) were more resistant to hypoxia- and anisomycin-induced apoptosis but remained equally susceptible to other stresses, including UV. Atf-2 −/− and Atf-2 +/− MEFs could not express a group of genes, such as Gadd45α, whose overexpression can induce apoptosis, in response to hypoxia. Atf-2 −/− MEFs also had a higher saturation density than wild-type cells and expressed lower levels of Maspin, the breast cancer tumor suppressor, which is also known to enhance cellular sensitivity to apoptotic stimuli. Atf-2 −/− MEFs underwent a lower degree of apoptosis at high cell density than wild-type cells. Atf-2 +/− mice were highly prone to mammary tumors that expressed reduced levels of Gadd45α and Maspin. The ATF-2 mRNA levels in human breast cancers were lower than those in normal breast tissue. Thus, ATF-2 acts as a tumor susceptibility gene of mammary tumors, at least partly, by activating a group of target genes, including Maspin and Gadd45α.

scholarly journals Quorum Sensing-Mediated and Growth Phase-Dependent Regulation of Metabolic Pathways in Hafnia alvei H4

2021 ◽  
Vol 12 ◽  
Author(s):  
Congyang Yan ◽  
Xue Li ◽  
Gongliang Zhang ◽  
Yaolei Zhu ◽  
Jingran Bi ◽  
...  
Keyword(s):  
Quorum Sensing ◽  
Cell Density ◽  
Growth Phase ◽  
Metabolic Pathways ◽  
High Cell Density ◽  
Dependent Manner ◽  
High Cell ◽  
Wild Type ◽  
Hafnia Alvei ◽  
Density Dependent

Quorum sensing (QS) is a widespread regulatory mechanism in bacteria used to coordinate target gene expression with cell density. Thus far, little is known about the regulatory relationship between QS and cell density in terms of metabolic pathways in Hafnia alvei H4. In this study, transcriptomics analysis was performed under two conditions to address this question. The comparative transcriptome of H. alvei H4 wild-type at high cell density (OD600 = 1.7) relative to low cell density (OD600 = 0.3) was considered as growth phase-dependent manner (GPDM), and the transcriptome profile of luxI/R deletion mutant (ΔluxIR) compared to the wild-type was considered as QS-mediated regulation. In all, we identified 206 differentially expressed genes (DEGs) mainly presented in chemotaxis, TCA cycle, two-component system, ABC transporters and pyruvate metabolism, co-regulated by the both density-dependent regulation, and the results were validated by qPCR and swimming phenotypic assays. Aside from the co-regulated DEGs, we also found that 59 DEGs, mediated by density-independent QS, function in pentose phosphate and histidine metabolism and that 2084 cell-density-dependent DEGs involved in glycolysis/gluconeogenesis and phenylalanine metabolism were influenced only by GPDM from significantly enriched analysis of transcriptome data. The findings provided new information about the interplay between two density-dependent metabolic regulation, which could assist with the formulation of control strategies for this opportunistic pathogen, especially at high cell density.

scholarly journals Assembly of XcpR in the Cytoplasmic Membrane Is Required for Extracellular Protein Secretion in Pseudomonas aeruginosa

1999 ◽  
Vol 181 (2) ◽  
pp. 382-388 ◽  
Author(s):  
Geneviève Ball ◽  
Virginie Chapon-Hervé ◽  
Sophie Bleves ◽  
Gérard Michel ◽  
Marc Bally
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Secretory Pathway ◽  
Cytoplasmic Membrane ◽  
Extracellular Proteins ◽  
Membrane Association ◽  
Stoichiometric Ratio ◽  
Gene Products ◽  
Type Ii ◽  
Wild Type ◽  
The Relationship

ABSTRACT A broad range of extracellular proteins secreted byPseudomonas aeruginosa use the type II or general secretory pathway (GSP) to reach the medium. This pathway requires the expression of at least 12 xcp gene products. XcpR, a putative nucleotide-binding protein, is essential for the secretion process across the outer membrane even though the protein contains no hydrophobic sequence that could target or anchor it to the bacterial envelope. For a better understanding of the relationship between XcpR and the other Xcp proteins which are located in the envelope, we have studied its subcellular localization. In a wild-type P. aeruginosa strain, XcpR was found associated with the cytoplasmic membrane. This association depends on the presence of the XcpY protein, which also appears to be necessary for XcpR stability. Functional complementation of an xcpY mutant required the XcpY protein to be expressed at a low level. Higher expression precluded the complementing activity of XcpY, although membrane association of XcpR was restored. This behavior suggested that an excess of free XcpY might interfere with the secretion by formation of inactive XcpR-XcpY complexes which cannot properly interact with their natural partners in the secretion machinery. These data show that a precise stoichiometric ratio between several components may be crucial for the functioning of the GSP.

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