Pattern Formation in the Blue-Green Alga Anabaena

1973 ◽  
Vol 13 (3) ◽  
pp. 637-649
Author(s):  
MICHAEL WILCOX ◽  
G. J. MITCHISON ◽  
R. J. SMITH
Keyword(s):  
Pattern Formation ◽  
Green Alga ◽  
Developmental Stages ◽  
Blue Green Alga ◽  
Inhibitory Substance ◽  
Vegetative Cells ◽  
Stage Of Development ◽  
Competitive Mechanism

We present further evidence for an interactive mechanism in the formation of the spaced pattern of heterocysts in Anabaena. The evidence comes from experiments which are an extension of those described earlier, in which filaments of the alga are broken near to a proheterocyst. We argue that a proheterocyst depends upon neighbouring vegetative cells for the removal of an inhibitory substance: when the proheterocyst is deprived of these supporting vegetative cells it will be forced to regress. We showed earlier that such regressions do occur in early proheterocysts when a filament is broken on one side only. We now find that advanced pro-heterocysts can be made to regress when double breakages are performed to leave small fragments containing the proheterocysts. The probability of a proheterocyst regressing is correlated with its stage of development and with the size of the fragment: the smaller the fragment, the more advanced is the stage at which regression will occur. To formulate this we have defined developmental stages in terms of ultrastructure and compiled the results of a diversity of breakage operations with the cells at these specified stages. Certain compounds affect the spacing of the heterocyst pattern, causing it to become wider or narrower. These compounds have the predicted effect upon regression frequencies, up-holding our assumption that regressions express an underlying competitive mechanism.

Pattern formation in the Blue-Green Alga, Anabaena

1973 ◽  
Vol 12 (3) ◽  
pp. 707-723 ◽  
Author(s):  
MICHAEL WILCOX ◽  
G. J. MITCHISON ◽  
R. J. SMITH
Keyword(s):  
Pattern Formation ◽  
Green Alga ◽  
Normal Growth ◽  
Growth Conditions ◽  
Inhibitory Effect ◽  
Blue Green Alga ◽  
Interactive Model ◽  
Differentiated Cells ◽  
Sequence Of Events

Filaments of Anabaena have a spaced pattern of differentiated cells called heterocysts, which is maintained as a filament grows by the regular determination of new heterocysts. By following the growth of every cell in a filament, we have identified proheterocysts (prospective heterocysts) at their earliest appearance, and described the sequence of events in the formation of the pattern. The determination of proheterocysts obeys 2 rules: (1) that there are inhibitory zones around pre-existing heterocysts, and (2) that only the smaller daughter of a division can become a heterocyst (all divisions are asymmetrical). There are, however, certain conditions in which these rules are over-ridden, where a pattern consisting of groups of consecutive proheterocysts is seen which resolves into a normal discrete pattern. This process is highly suggestive of interaction between developing cells. We have tested this hypothesis in normal growth conditions by breaking filaments near to early proheterocysts, on the assumption that this will cause a build-up of inhibitory effect of the cell upon itself. It is found that these cells regress, losing their differentiated character and dividing. We therefore propose an interactive model for pattern formation in Anabaena.

Soluble Nitrogenase from Vegetative Cells of the Blue–Green Alga Anabaena cylindrica

Nature ◽  
1970 ◽  
Vol 225 (5239) ◽  
pp. 1253-1254 ◽  
Author(s):  
R. V. SMITH ◽  
M. C. W. EVANS
Keyword(s):  
Green Alga ◽  
Blue Green Alga ◽  
Anabaena Cylindrica ◽  
Vegetative Cells

Effect of Iron Limitation on the Ultrastructure of Agmenellum Quadruplicatum

1981 ◽  
Vol 39 ◽  
pp. 410-411
Author(s):  
L. P. Hardie ◽  
D. L. Balkwill ◽  
S. E. Stevens
Keyword(s):  
Growth Medium ◽  
Green Alga ◽  
Natural Habitat ◽  
Iron Limitation ◽  
Natural Environments ◽  
Blue Green Alga ◽  
Marine Cyanobacterium ◽  
Natural Systems ◽  
Thin Sectioning ◽  
Agmenellum Quadruplicatum

Agmenellum quadruplicatum is a unicellular, non-nitrogen-fixing, marine cyanobacterium (blue-green alga). The ultrastructure of this organism, when grown in the laboratory with all necessary nutrients, has been characterized thoroughly. In contrast, little is known of its ultrastructure in the specific nutrient-limiting conditions typical of its natural habitat. Iron is one of the nutrients likely to limit this organism in such natural environments. It is also of great importance metabolically, being required for both photosynthesis and assimilation of nitrate. The purpose of this study was to assess the effects (if any) of iron limitation on the ultrastructure of A. quadruplicatum. It was part of a broader endeavor to elucidate the ultrastructure of cyanobacteria in natural systemsActively growing cells were placed in a growth medium containing 1% of its usual iron. The cultures were then sampled periodically for 10 days and prepared for thin sectioning TEM to assess the effects of iron limitation.

Effects of amino acids on the blue-green alga (cyanobacteria) Tolypothrix scytonemoides (Gardner) Geitler

2006 ◽  
Vol 8 (3) ◽  
pp. 286-293
Author(s):  
Uma Maheshwari Rajendran ◽  
Elango Kathirvel ◽  
Anand Narayanaswamy
Keyword(s):  
Amino Acids ◽  
Green Alga ◽  
Blue Green Alga

scholarly journals Crayfish hemocytes develop along the granular cell lineage

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fang Li ◽  
Zaichao Zheng ◽  
Hongyu Li ◽  
Rongrong Fu ◽  
Limei Xu ◽  
...  
Keyword(s):  
Developmental Stages ◽  
Cell Lineage ◽  
Granular Cell ◽  
Marker Genes ◽  
Hematopoietic Tissue ◽  
Differentiated Cells ◽  
Stage Of Development ◽  
Almost All ◽  
Relationship Of

AbstractDespite the central role of hemocytes in crustacean immunity, the process of hemocyte differentiation and maturation remains unclear. In some decapods, it has been proposed that the two main types of hemocytes, granular cells (GCs) and semigranular cells (SGCs), differentiate along separate lineages. However, our current findings challenge this model. By tracking newly produced hemocytes and transplanted cells, we demonstrate that almost all the circulating hemocytes of crayfish belong to the GC lineage. SGCs and GCs may represent hemocytes of different developmental stages rather than two types of fully differentiated cells. Hemocyte precursors produced by progenitor cells differentiate in the hematopoietic tissue (HPT) for 3 ~ 4 days. Immature hemocytes are released from HPT in the form of SGCs and take 1 ~ 3 months to mature in the circulation. GCs represent the terminal stage of development. They can survive for as long as 2 months. The changes in the expression pattern of marker genes during GC differentiation support our conclusions. Further analysis of hemocyte phagocytosis indicates the existence of functionally different subpopulations. These findings may reshape our understanding of crustacean hematopoiesis and may lead to reconsideration of the roles and relationship of circulating hemocytes.

scholarly journals Uridine Diphosphate Galacturonate 4-Epimerase from the Blue-Green Alga Anabaena flos-aquae

1974 ◽  
Vol 249 (8) ◽  
pp. 2366-2372
Author(s):  
Mary A. Gaunt ◽  
Utpalendu S. Maitra ◽  
Helmut Ankel
Keyword(s):  
Green Alga ◽  
Uridine Diphosphate ◽  
Blue Green Alga
Sign in / Sign up

Export Citation Format

Share Document