scholarly journals Multicellular behavior enables cooperation in microbial cell aggregates

2019 ◽  
Author(s):  
Ali Ebrahimi ◽  
Julia Schwartzman ◽  
Otto X. Cordero
Keyword(s):  
Extracellular Enzymes ◽  
Hollow Structure ◽  
Cell Aggregation ◽  
Large Cell ◽  
Cell Aggregates ◽  
Diffusion Limitation ◽  
Internal Structures ◽  
High Enzyme ◽  
Dependent Growth ◽  
Secretion Rates

SummaryDuring the degradation of biological materials such as biopolymers, extracellular enzymes liberate oligosaccharides that act as common goods and become available for all cells in the local neighborhood. This phenomenon can lead to cooperative growth, whereby cell-cell aggregation increases both the per-capita availability of resources and the per cell growth rate. However, aggregation can also have detrimental consequences for growth, as gradients form within aggregates limiting the resource accessibility. We used a computational model to show that high bacterial densities and high enzyme secretion rates restrict cooperation in aggregates larger than 10μm, due to the emergence of polymer and oligomer counter-gradients. We compared these predictions against experiments performed with two well-studied alginate degrading Vibrios, one of which displayed a strong density dependent growth. We observed that both strains can form large aggregates (<50μm), overcoming diffusion limitation by rearranging their internal structure. The non-cooperative, strong enzyme producer formed aggregates with internal channels that allowed exchange between the bulk environment and the aggregate core, whereas the cooperative, weak enzyme producer formed dense aggregates that developed a hollow structure as they grew. These internal structures allowed cells to avoid overcrowded areas near the core, enabling the development of large cell aggregates. Our study shows that bacterial behavior can help overcome competition imposed by resource gradients within cell aggregates.

scholarly journals Multicellular behaviour enables cooperation in microbial cell aggregates

2019 ◽  
Vol 374 (1786) ◽  
pp. 20190077 ◽  
Author(s):  
Ali Ebrahimi ◽  
Julia Schwartzman ◽  
Otto X. Cordero
Keyword(s):  
Alginate Lyase ◽  
Cell Aggregation ◽  
Microbial Populations ◽  
Cell Aggregates ◽  
Vibrio Splendidus ◽  
Diffusion Limitation ◽  
Dense Cell ◽  
Per Capita ◽  
Active Swimming ◽  
Hydrolysis Of

Oligosaccharides produced from the extracellular hydrolysis of biological materials can act as common goods that promote cooperative growth in microbial populations, whereby cell–cell aggregation increases both the per capita availability of resources and the per-cell growth rate. However, aggregation can also have detrimental consequences for growth, as gradients form within aggregates limiting the resource accessibility. We built a computational model, which predicts cooperation is restricted in dense cell aggregates larger than 10 µm because of the emergence of polymer and oligomer counter gradients. We compared these predictions to experiments performed with two well-studied alginate-degrading strains of Vibrio splendidus , which varied in their ability to secrete alginate lyase. We observed that both strains can form large aggregates (less than 50 µm), overcoming diffusion limitation by rearranging their internal structure. The stronger enzyme producer grew non-cooperatively and formed aggregates with internal channels that allowed exchange between the bulk environment and the aggregate, whereas the weak enzyme producer showed strongly cooperative growth and formed dense aggregates in which cells near the core mixed by active swimming. Our simulations suggest that the mixing and channelling reduce diffusion limitation and allow cells to uniformly grow in aggregates. Together, these data demonstrate that bacterial behaviour can help overcome competition imposed by resource gradients within cell aggregates. This article is part of a discussion meeting issue ‘Single cell ecology’.

Effects on Erythrocyte Aggregation and Blood Coagulation from Iohexol Solutions with and without Sodium Chloride

1995 ◽  
Vol 36 (2) ◽  
pp. 204-209
Author(s):  
C.-M. Chai ◽  
T. Almén ◽  
P. Aspelin ◽  
L. Bååth
Keyword(s):  
Sodium Chloride ◽  
Blood Coagulation ◽  
Glucose Solution ◽  
Cell Aggregation ◽  
Test Solution ◽  
Erythrocyte Aggregation ◽  
Cell Aggregates ◽  
Red Cell ◽  
Red Blood Cell Aggregation ◽  
Osmotic Effects

Solutions of the nonionic monomeric contrast medium iohexol (300 mg I/ml) with and without added NaCl were investigated for effects on red blood cell aggregation and blood coagulation. Three volumes of a test solution were mixed in test tubes with one volume of human blood. During 30 min samples of the mixture were taken for investigation. Six test solutions were used: 1) iohexol, 2) iohexol+glucose 280 mM, 3) iohexol+NaCl 150 mM, 4) glucose 280 mM, 5) glucose 140 mM+NaCl 75 mM, 6) NaCl 150 mM. Test solutions with NaCl caused no aggregation. Test solutions without NaCl always caused macroscopic red cell aggregates. These aggregates always disappeared when saline was added to the sample. The macroscopic red cell aggregates could be dispersed to microscopic aggregates by shaking the test tubes. During the next 30 min macroscopic aggregates returned in the glucose solution but not in the iohexol solutions. In 30 min, blood mixed with iohexol solutions never coagulated while blood layered on top of the same iohexol solutions always coagulated. Blood mixed with solutions 5 and 6, both without iohexol, always coagulated. It is concluded that adding 150 mM NaCl to iohexol did not eliminate its ability to antico-agulate whole blood, but inhibited its ability to aggregate red cells. This inhibition was not caused by the osmotic effects of the added NaCl.

Modulation by Heparin of the Interaction of the A1 Domain of von Willebrand Factor With Glycoprotein Ib

Blood ◽  
1999 ◽  
Vol 94 (12) ◽  
pp. 4186-4194 ◽  
Author(s):  
Christelle Perrault ◽  
Nadine Ajzenberg ◽  
Paulette Legendre ◽  
Ghassem Rastegar-Lari ◽  
Dominique Meyer ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Cell Aggregation ◽  
Cell Aggregates ◽  
Critical Determinant ◽  
Amino Terminal ◽  
A Cell ◽  
A1 Domain ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Amino Terminal Fragment

Abstract The conformation of the A1 domain of von Willebrand factor (vWF) is a critical determinant of its interaction with the glycoprotein (GP) Ib/V/IX complex. To better define the regulatory mechanisms of vWF A1 domain binding to the GPIb/V/IX complex, we studied vWF-dependent aggregation properties of a cell line overexpressing the GPIb, GPIbβ, and GPIX subunits (CHO-GPIbβ/IX cells). We found that CHO-GPIbβ/IX cell aggregation required the presence of both soluble vWF and ristocetin. Ristocetin-induced CHO-GPIbβ/IX cell aggregation was completely inhibited by the recombinant VCL fragment of vWF that contains the A1 domain. Surprisingly, the substitution of heparin for ristocetin resulted in the formation of CHO-GPIbβ/IX cell aggregates. Using monoclonal antibodies blocking vWF interaction with GPIb/V/IX or mocarhagin, a venom metalloproteinase that removes the amino-terminal fragment of GPIb extending from aa 1 to 282, we demonstrated that both ristocetin- and heparin-induced aggregations involved an interaction between the A1 domain of vWF and the GPIb subunit of the GPIb/V/IX complex. The involvement of heparin in cell aggregation was also demonstrated after treatment of heparin with heparinase that abolished CHO-GPIbβ/IX cell aggregation. These results indicated that heparin was able to induce vWF-dependent CHO-GPIbβ/IX cell aggregation. In conclusion, we demonstrated that heparin is capable of positively modulating the vWF interaction with the GPIb/V/IX complex.

Intercellular adhesion and formation of aggregates in normal and Talpid-3 mutant chick limb mesenchyme

1975 ◽  
Vol 18 (1) ◽  
pp. 97-111
Author(s):  
D.A. Ede ◽  
O.P. Flint
Keyword(s):  
Electron Micrographs ◽  
Large Cell ◽  
Cell Aggregates ◽  
Normal Cells ◽  
Cell Contacts ◽  
Cell Numbers ◽  
Limb Mesenchyme ◽  
Couette Viscometer ◽  
Mesenchyme Cells ◽  
Internal Architecture

It is demonstrated, using the Couette viscometer method, that talpid-3 mutant chick wing mesenchyme cells are more adhesive to one another than are normal cells. The relation of this to differences in the size and shape, and the internal architecture, of aggregates produced in rotation cultures of these cells was investigated. Sequences of sections through aggregates in all stages of formation, from 2-cell aggregates up to those with large cell numbers, were prepared. These confirm the theoretically predicted relationships among adhering cells which would produce the observed small, spherical talpid-3 aggregates and the larger, unevenly shaped normal aggregates. The cell contacts are further analysed with electron micrographs.

NEW BACTERIAL AGGREGATE-FORMING PRODUCER OF POLY-3-HYDROXYBUTYRATE

2020 ◽  
pp. 422-423
Author(s):  
A. Pshenichnikova
Keyword(s):  
Suspension Culture ◽  
Cell Aggregation ◽  
Methylotrophic Bacterium ◽  
Carotenoid Pigment ◽  
Cell Aggregates ◽  
Bacterial Aggregate

The growth and accumulation of carotenoid pigment and poly-3-hydroxybutyrate by a new strain of pink-colored facultative methylotrophic bacterium Methylorubrum extorquens LP in suspension culture and in cell aggregates were studied. The parameters that promote cell aggregation and the formation of poly-3-hydroxybutyrate have been determined.

Influence of fibrinogen on flow properties of erythrocyte suspensions

1964 ◽  
Vol 207 (5) ◽  
pp. 1035-1040 ◽  
Author(s):  
Roe E. Wells ◽  
Thomas H. Gawronski ◽  
Paul J. Cox ◽  
Richard D. Perera
Keyword(s):  
Shear Stress ◽  
Shear Rate ◽  
Cell Aggregation ◽  
Cell Suspensions ◽  
Fibrinogen Concentration ◽  
Sedimentation Rates ◽  
Cell Aggregates ◽  
Red Cell ◽  
Flow Properties ◽  
Yield Value

The influence of fibrinogen on the flow properties of red cell suspensions (hematocrit 41) was studied by viscometry at low rates of shear (0.1–20 sec–1). These findings were correlated with sedimentation rates and photomicrographical studies of cell aggregation. Fibrinogen concentration was varied from 0.3 to 2.0 g/100 ml. The viscosity of the pure solutions of fibrinogen was independent of shear rate, ranging from 0.87 to 1.7 centipoise (cp) at 37 C. The viscosity of the cell suspensions at 10 sec–1 varied from 4.3 cp in 0.3 g/100 ml fibrinogen to 14 cp in 2 g/100 ml fibrinogen. All suspensions were markedly dependent on shear rate, viscosity increasing in exponential-like fashion as shear rate decreased. Extrapolation of plots of shear stress1/2 versus shear rate1/2 revealed the suspensions to sustain a finite stress without deformation or flow, the "yield value" increasing as fibrinogen concentration increased. Photomicrographs of dilute cell suspensions revealed the formation of cell aggregates and rouleaux, increasing in size and descent velocity as fibrinogen concentration increased.

CD43 Interacts With Moesin and Ezrin and Regulates Its Redistribution to the Uropods of T Lymphocytes at the Cell-Cell Contacts

Blood ◽  
1998 ◽  
Vol 91 (12) ◽  
pp. 4632-4644 ◽  
Author(s):  
Juan M. Serrador ◽  
Marta Nieto ◽  
José L. Alonso-Lebrero ◽  
Miguel A. del Pozo ◽  
Javier Calvo ◽  
...  
Keyword(s):  
T Cell ◽  
T Lymphocytes ◽  
Binding Proteins ◽  
Cell Aggregation ◽  
Actin Binding ◽  
Cell Aggregates ◽  
Actin Binding Proteins ◽  
Cell Contacts ◽  
T Lymphoblasts ◽  
Cell Cell

Abstract Chemokines as well as the signaling through the adhesion molecules intercellular adhesion molecule (ICAM)-3 and CD43 are able to induce in T lymphocytes their switching from a spherical to a polarized motile morphology, with the formation of a uropod at the rear of the cell. We investigated here the role of CD43 in the regulation of T-cell polarity, CD43-cytoskeletal interactions, and lymphocyte aggregation. Pro-activatory anti-CD43 monoclonal antibody (MoAb) induced polarization of T lymphocytes with redistribution of CD43 to the uropod and the CCR2 chemokine receptor to the leading edge of the cell. Immunofluorescence analysis showed that all three ezrin-radixin-moesin (ERM) actin-binding proteins localized in the uropod of both human T lymphoblasts stimulated with anti-CD43 MoAb and tumor-infiltrating T lymphocytes. Radixin localized at the uropod neck, whereas ezrin and moesin colocalized with CD43 in the uropod. Biochemical analyses showed that ezrin and moesin coimmunoprecipitated with CD43 in T lymphoblasts. Furthermore, in these cells, the CD43-associated moesin increased after stimulation through CD43. The interaction of moesin and ezrin with CD43 was specifically mediated by the cytoplasmic domain of CD43, as shown by precipitation of both ERM proteins with a GST-fusion protein containing the CD43 cytoplasmic tail. Videomicroscopy analysis of homotypic cell aggregation induced through CD43 showed that cellular uropods mediate cell-cell contacts and lymphocyte recruitment. Immunofluorescence microscopy performed in parallel showed that uropods enriched in CD43 and moesin localized at the cell-cell contact areas of cell aggregates. The polarization and homotypic cell aggregation induced through CD43 was prevented by butanedione monoxime, indicating the involvement of myosin cytoskeleton in these phenomena. Altogether, these data indicate that CD43 plays an important regulatory role in remodeling T-cell morphology, likely through its interaction with actin-binding proteins ezrin and moesin. In addition, the redistribution of CD43 to the uropod region of migrating lymphocytes and during the formation of cell aggregates together with the enhancing effect of anti-CD43 antibodies on lymphocyte cell recruitment suggest that CD43 plays a key role in the regulation of cell-cell interactions during lymphocyte traffic.

Modulation by Heparin of the Interaction of the A1 Domain of von Willebrand Factor With Glycoprotein Ib

Blood ◽  
1999 ◽  
Vol 94 (12) ◽  
pp. 4186-4194
Author(s):  
Christelle Perrault ◽  
Nadine Ajzenberg ◽  
Paulette Legendre ◽  
Ghassem Rastegar-Lari ◽  
Dominique Meyer ◽  
...  
Keyword(s):  
Von Willebrand Factor ◽  
Cell Aggregation ◽  
Cell Aggregates ◽  
Critical Determinant ◽  
Amino Terminal ◽  
A Cell ◽  
A1 Domain ◽  
Von Willebrand ◽  
Willebrand Factor ◽  
Amino Terminal Fragment

The conformation of the A1 domain of von Willebrand factor (vWF) is a critical determinant of its interaction with the glycoprotein (GP) Ib/V/IX complex. To better define the regulatory mechanisms of vWF A1 domain binding to the GPIb/V/IX complex, we studied vWF-dependent aggregation properties of a cell line overexpressing the GPIb, GPIbβ, and GPIX subunits (CHO-GPIbβ/IX cells). We found that CHO-GPIbβ/IX cell aggregation required the presence of both soluble vWF and ristocetin. Ristocetin-induced CHO-GPIbβ/IX cell aggregation was completely inhibited by the recombinant VCL fragment of vWF that contains the A1 domain. Surprisingly, the substitution of heparin for ristocetin resulted in the formation of CHO-GPIbβ/IX cell aggregates. Using monoclonal antibodies blocking vWF interaction with GPIb/V/IX or mocarhagin, a venom metalloproteinase that removes the amino-terminal fragment of GPIb extending from aa 1 to 282, we demonstrated that both ristocetin- and heparin-induced aggregations involved an interaction between the A1 domain of vWF and the GPIb subunit of the GPIb/V/IX complex. The involvement of heparin in cell aggregation was also demonstrated after treatment of heparin with heparinase that abolished CHO-GPIbβ/IX cell aggregation. These results indicated that heparin was able to induce vWF-dependent CHO-GPIbβ/IX cell aggregation. In conclusion, we demonstrated that heparin is capable of positively modulating the vWF interaction with the GPIb/V/IX complex.

scholarly journals The Grb2/Mek Pathway Represses Nanog in Murine Embryonic Stem Cells

2006 ◽  
Vol 26 (20) ◽  
pp. 7539-7549 ◽  
Author(s):  
Takashi Hamazaki ◽  
Sarah M. Kehoe ◽  
Toru Nakano ◽  
Naohiro Terada
Keyword(s):  
Es Cells ◽  
Tyrosine Phosphatase ◽  
Embryonic Stem ◽  
Homeobox Gene ◽  
Cell Aggregation ◽  
Cell Aggregates ◽  
Es Cell ◽  
Sodium Vanadate ◽  
Primitive Endoderm ◽  
Endoderm Differentiation

ABSTRACT The homeobox gene Nanog is a key intrinsic determinant of self renewal in embryonic stem (ES) cells, and its repression leads ES cells to selectively differentiate into primitive endoderm. Although Nanog repression occurs at the outermost layer of ES cell aggregates independent of the leukemia inhibitory factor (LIF)/STAT3 pathway, it is largely undetermined what external cues and intracellular signals cause the event. Of interest, addition of the tyrosine phosphatase inhibitor, sodium vanadate, selectively repressed Nanog transcription without any detectable changes in upstream transcriptional regulators Oct3/4 and Sox2. Furthermore, sodium vanadate induced primitive endoderm differentiation, even in the inner cells of ES cell aggregates. Expression of Gata6 and Zfp42, two putative downstream Nanog effectors, was also increased and decreased by the addition of sodium vanadate, respectively, but these changes were eliminated by exogenous Nanog expression. The effects of sodium vanadate were abrogated by Grb2 deficiency or by the addition of the Mek inhibitor, PD98059. Indeed, PD98059 prevented Nanog repression induced by ES cell aggregation as well. Furthermore, transfection of a constitutive active Mek mutant into ES cells induced Nanog repression and primitive endoderm differentiation. These data indicate that the Grb2/Mek pathway primarily mediates Nanog gene repression upon ES cell differentiation into primitive endoderm.

scholarly journals Mutation of the gene encoding a major outer-membrane protein in Xanthomonas campestris pv. campestris causes pleiotropic effects, including loss of pathogenicity

Microbiology ◽  
2010 ◽  
Vol 156 (9) ◽  
pp. 2842-2854 ◽  
Author(s):  
Yih-Yuan Chen ◽  
Chieh-Hao Wu ◽  
Juey-Wen Lin ◽  
Shu-Fen Weng ◽  
Yi-Hsiung Tseng
Keyword(s):  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Xanthomonas Campestris ◽  
Extracellular Enzymes ◽  
Surface Deformation ◽  
Cell Signalling ◽  
Cell Aggregation ◽  
Major Outer Membrane Protein ◽  
Gene Encoding

Xanthomonas campestris pv. campestris (Xcc) is the phytopathogen that causes black rot in crucifers. The xanthan polysaccharide and extracellular enzymes produced by this organism are virulence factors, the expression of which is upregulated by Clp (CRP-like protein) and DSF (diffusible signal factor), which is synthesized by RpfF. It is also known that biofilm formation/dispersal, regulated by the effect of controlled synthesis of DSF on cell–cell signalling, is required for virulence. Furthermore, a deficiency in DSF causes cell aggregation with concomitant production of a gum-like substance that can be dispersed by addition of DSF or digested by exogenous endo-β-1,4-mannanase expressed by Xcc. In this study, Western blotting of proteins from a mopB mutant (XcMopB) showed Xcc MopB to be the major outer-membrane protein (OMP); Xcc MopB shared over 97 % identity with homologues from other members of Xanthomonas. Similarly to the rpfF mutant, XcMopB formed aggregates with simultaneous production of a gummy substance, but these aggregates could not be dispersed by DSF or endo-β-1,4-mannanase, indicating that different mechanisms were involved in aggregation. In addition, XcMopB showed surface deformation, altered OMP composition, impaired xanthan production, increased sensitivity to stressful conditions including SDS, elevated temperature and changes in pH, reduced adhesion and motility and defects in pathogenesis. The finding that the major OMP is required for pathogenicity is unprecedented in phytopathogenic bacteria.

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