The green hydra symbiosis. VII. Conservation of the host cell habitat by the symbiotic algae

1982 ◽  
Vol 216 (1205) ◽  
pp. 415-426 ◽  
Keyword(s):  
Host Cell ◽  
Lysosomal Degradation ◽  
Normal Complement ◽  
Calcofluor White ◽  
Digestive Cells ◽  
Symbiotic Algae ◽  
Green Hydra ◽  
Fluorescent Agent ◽  
Almost All ◽  
Cell Base

Freshly isolated ‘European’ algae phagocytosed by digestive cells of ‘European’ green hydra were distinguished from the pre-existing popu­lation of algae by prestaining with the fluorescent agent Calcofluor White. Only a small number of phagocytosed ‘European’ algae or algae cultured from Paramecium bursaria avoided lysosomal degradation and were transported to the cell base in symbiotic digestive cells, although in aposymbionts up to 50% of phagocytosed algae were transported. Degradation of almost all phagocytosed algae also occurred in digestive cells of hydra containing only half the normal complement of algae, and in those of hydra symbiotic with algae cultured from Paramecium . The presence of algae at the bases of digestive cells appears to negate the mechanism by which potentially symbiotic algae normally avoid lysosomal attack. This protects the host cell and its symbionts from invasion by ‘foreign’ algae and suggests that once established the green hydra symbiosis is conservative in nature.

The green hydra symbiosis. V. Stages in the intracellular recognition of algal symbionts by digestive cells

1982 ◽  
Vol 216 (1202) ◽  
pp. 7-23 ◽  
Keyword(s):  
Host Cell ◽  
Transport Mechanism ◽  
Digestive Cell ◽  
Digestive Cells ◽  
Maltose Transport ◽  
Green Hydra ◽  
Algal Symbionts ◽  
Wide Range ◽  
Cell Base

Aposymbiotic (alga-free) green hydra may be reinfected by injecting a suspension of Chlorella symbionts into their coelenterons. Digestive cells could phagocytose a wide range of Chlorella types, but transport to the cell base, where the symbionts normally reside, was limited to algae that release detectable amounts of maltose. Transport of their own symbionts was inhibited when maltose release was curtailed by prolonged pretreatment with a photosynthetic inhibitor. After phagocytosis, only about half of their own symbionts were transported, the rest remaining at the digestive cell apex where they disintegrated. This phenomenon was termed sorting. It was not due to damage of algae during isolation, nor to saturation of the transport mechanism. A further stage of discrimination was observed to take place up to 5 days after injection; some symbionts that had been transported to the cell bases were removed to the apices and disintegrated or were ejected (re-sorting). It is concluded that recognition of suitable algae is unlikely to involve identification of a single algal character by the European digestive cells. The establishment of the symbiosis may depend upon a number of algal properties and interactions within the host cell.

scholarly journals Temporal relationships of host cell and algal mitosis in the green hydra symbiosis

1982 ◽  
Vol 58 (1) ◽  
pp. 423-431
Author(s):  
P.J. McAuley
Keyword(s):  
Cell Division ◽  
Host Cell ◽  
Digestive Cell ◽  
Digestive Cells ◽  
Symbiotic Algae ◽  
Green Hydra ◽  
Temporal Relationships ◽  
Dividing Cells ◽  
Cell Mitosis ◽  
Mitotic Cells

In fed hydra or excised regenerating peduncles there are increases in the mitotic indices of both digestive cells and the symbiotic algae that reside within them. Conversely, algal and digestive cell mitotic indices decrease in starved hydra. The temporal relationships of algal and host cell division differ in fed hydra and regenerating peduncles. After feeding, algal and digestive cell mitotic indices both reach a peak at about the same time; during regeneration, first the algae and then the digestive cells divide. Thus, mitotic digestive cells in regenerating peduncles contain more algae than those in gastric regions of fed hydra. However, in both cases mitotic digestive cells contain more algae than non-mitotic cells. The algae appear to be partitioned at random between daughter digestive cells at teleophase. It is suggested that the division of the symbiotic algae is closely related to that of the digestive cells in which they maintained. Mitosis of algae is stimulated by host cell mitosis, but in non-dividing cells algal mitosis is restricted. Possible mechanisms by which the host digestive cells could restrict algal division are discussed.

Partitioning of symbiotic Chlorella at host cell telophase in the green hydra symbiosis

1990 ◽  
Vol 329 (1252) ◽  
pp. 47-53 ◽  
Keyword(s):  
Cell Division ◽  
Host Cell ◽  
Daughter Cell ◽  
Control Cell ◽  
Culture Conditions ◽  
Digestive Cells ◽  
Density Dependent ◽  
Green Hydra ◽  
The Mean ◽  
Control Cell Division

Although there is much evidence that green hydra digestive cells control cell division of their Chlorella symbionts, so that the symbionts divide only at host cell division, it is not clear how the population size of symbionts (numbers per cell) is regulated. In constant culture conditions the mean number of symbionts per cell also remains constant, but with a very large variance about the mean. The way in which symbionts are partitioned at host cell division appears to account for that variation. By counting numbers of Chlorella in daughter cells at late telophase it was found that partitioning of Chlorella symbionts was not symmetrical, but at random, closely following that predicted by the binomial distribution if it is assumed that each symbiont had an equal probability of entering either host daughter cell. A better fit to the predicted distribution was obtained from observations of partition in digestive cells from excised regenerating peduncles than in those from recently fed gastric regions, possibly because in the former, algae have completed their division before the host cell divides, while in the latter algal and host cell division takes place at the same time. There was only a small effect of differences in daughter cell volume on numbers of symbionts received, but comparison of variance and coefficient of variation of numbers of algae in mother (post-algal division, pre-partition) and daughter telophase digestive cells (pre-division, post-partition) suggested that algal division at host mitosis was density dependent. Random partitioning of algae at host cell telophase would account for the wide variation in numbers of algae per cell, and compensatory density-dependent algal division at the next host cell mitosis would ensure stability of the mean algal population.

The green hydra symbiosis. IV. Entry of symbionts into digestive cells

1982 ◽  
Vol 216 (1202) ◽  
pp. 1-6 ◽  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Plasma Membrane ◽  
Digestive Cell ◽  
Particle Type ◽  
Digestive Cells ◽  
Symbiotic Algae ◽  
Green Hydra ◽  
Different Types ◽  
Scanning Electron

Scanning electron microscopy showed that particles, including symbiotic algae, non-symbiotic algae and latex spheres, entered digestive cells of European green hydra by two different types of phagocytosis: (i) they sank into crater-like formations of the digestive-cell surface; or (ii) they were enveloped by raised, funnel-like extensions of plasma membrane. The morphology selected did not depend on particle type: there was no evidence for specific recognition of symbiotic algae during phagocytosis.

The cell cycle of symbiotic Chlorella. III. Numbers of algae in green hydra digestive cells are regulated at digestive cell division

1986 ◽  
Vol 85 (1) ◽  
pp. 63-71
Author(s):  
P.J. McAuley
Keyword(s):  
Cell Division ◽  
Host Cell ◽  
Algal Cell ◽  
Host Cells ◽  
Digestive Cell ◽  
Digestive Cells ◽  
Daughter Cells ◽  
Green Hydra ◽  
Mother And Daughter ◽  
Chlorella Algae

Regression analysis of the relationship between the size of interphase and mitotic digestive cells of green hydra, and the numbers and total volume of the symbiotic Chlorella algae they contain showed a partial correlation only, suggesting that numbers of algae per cell are not regulated by limiting them to a specific proportion of the host cell, and that the variation observed in numbers of algae per cell is not due to variation in host cell size. After hydra were fed, which stimulates algae and digestive cells to divide at the same time, numbers of algae per cell were higher in prophase than in interphase cells, and numbers increased as mitosis proceeded. In excised regenerating peduncles algae divide before digestive cells, and at the onset of digestive cell division mitotic cells were found to contain almost twice the number of algae as before excision. Thus, almost all of the algal cell division necessary to maintain a constant population size was associated with digestive cell division. Analysis of variance in numbers of algae in telophase mother and daughter cells suggested that the proportion of algae dividing as a result of host cell mitosis was greater in digestive cells with few algae than in those with many algae. The fact that the mechanism controlling the proportion of algae dividing in host cells is expressed at host cell division and is manifested in the daughter cells may contribute to wide variation in numbers of algae per cell.

Stress tolerance alteration in the freshwater cnidarian green hydra (Hydra viridissima) via symbiotic algae mutagenesis

Symbiosis ◽  
2020 ◽  
Vol 82 (3) ◽  
pp. 189-199
Author(s):  
Siao Ye ◽  
Meenakshi Bhattacharjee ◽  
Evan Siemann
Keyword(s):  
Stress Tolerance ◽  
Symbiotic Algae ◽  
Green Hydra

The cell cycle of symbiotic Chlorella. I. The relationship between host feeding and algal cell growth and division

1985 ◽  
Vol 77 (1) ◽  
pp. 225-239
Author(s):  
P.J. McAuley
Keyword(s):  
Cell Division ◽  
Cell Growth ◽  
Host Cell ◽  
Algal Cell ◽  
Host Cells ◽  
Digestive Cell ◽  
Host Feeding ◽  
Digestive Cells ◽  
Division Factor ◽  
Cell Mitosis

When green hydra were starved, cell division of the symbiotic algae within their digestive cells was inhibited, but algal cell growth, measured as increase in either mean volume or protein content per cell, was not. Therefore, control of algal division by the host digestive cells must be effected by direct inhibition of algal mitosis rather than by controlling algal cell growth. The number of algae per digestive cell increased slightly during starvation, eventually reaching a new stable level. A number of experiments demonstrated that although there was a relationship between host cell and algal mitosis, this was not causal: the apparent entrainment of algal mitosis to that of the host cells could be disrupted. Thus, there was a delay in algal but not host cell mitosis when hydra were fed after prolonged starvation, and algae repopulated starved hydra with lower than normal numbers of algae (reinfected aposymbionts or hydra transferred to light after growth in continuous darkness). Two experiments demonstrated a direct stimulation of algal cell division by host feeding. Relationships of algal and host cell mitosis to numbers of Artemia digested per hydra were different, and in hydra fed extracted Artemia algal, but not host cell, mitosis was reduced in comparison to that in control hydra fed live shrimp. It is proposed that algal division may be dependent on a division factor, derived from host digestion of prey, whose supply is controlled by the host cells. Numbers of algae per cell would be regulated by competition for division factor, except at host cell mitosis, when the algae may have temporarily uncontrolled access to host pools of division factor. The identity of the division factor is not known, but presumably is a metabolite needed by both host cells and algae.

Regulation of intracellular algae by various strains of the symbiotic Hydra viridissima

1986 ◽  
Vol 85 (1) ◽  
pp. 187-195
Author(s):  
P. Bossert ◽  
K.W. Dunn
Keyword(s):  
Host Cell ◽  
Mitotic Index ◽  
Large Strain ◽  
Green Hydra

In observations on three strains of green hydra, the host and the algal mitotic index is closely coordinated only for the smallest. As the hydra strain size increases the coordination of host and algal mitosis progressively breaks down, first in timing for a medium-sized strain and then in rate for a large strain. Despite disparities between host and algal mitotic index, the number of algae per host cell remains constant in all strains during the interval measured. To account for this constancy we suggest that the hydra may either prolong the duration of the algal tetraspore stage or cull excess algae.

scholarly journals Infection with Toxoplasma gondii Bradyzoites Has a Diminished Impact on Host Transcript Levels Relative to Tachyzoite Infection

2006 ◽  
Vol 75 (2) ◽  
pp. 634-642 ◽  
Author(s):  
A. E. Fouts ◽  
J. C. Boothroyd
Keyword(s):  
Toxoplasma Gondii ◽  
Host Cell ◽  
Transcript Level ◽  
Infected Host ◽  
Host Immune System ◽  
Cell Microarrays ◽  
Macrophage Colony ◽  
Lower Magnitude ◽  
Almost All

ABSTRACT Toxoplasma gondii, an intracellular pathogen, has the potential to infect nearly every warm-blooded animal but rarely causes morbidity. The ability for the parasite to convert to the bradyzoite stage and live inside slow-growing cysts that can go unnoticed by the host immune system allows for parasite persistence for the life of the infected host. This intracellular survival likely necessitates host cell modulation, and tachyzoites are known to modify a number of signaling cascades within the host to promote parasite survival. Little is known, however, about how bradyzoites manipulate their host cell. Microarrays were used to profile the host transcriptional changes caused by bradyzoite infection and compared to those of tachyzoite-infected and uninfected hosts cells 2 days postinfection in vitro. Infection resulted in chemokine, cytokine, extracellular matrix, and growth factor transcript level changes. A small group of genes were specifically induced by tachyzoite infection, including granulocyte-macrophage colony-stimulating factor, BCL2-related protein A1, and interleukin-24. Bradyzoite infection yielded only about half the changes seen with tachyzoite infection, and those changes that did occur were almost all of lower magnitude than those induced by tachyzoites. These results suggest that bradyzoites lead a more stealthy existence within the infected host cell.

The role of algal antigenic determinants in the recognition of potential algal symbionts by cells of Chlorohydra

1979 ◽  
Vol 35 (1) ◽  
pp. 367-379
Author(s):  
R.R. Pool
Keyword(s):  
Cell Surface ◽  
Algal Cell ◽  
Antigenic Determinants ◽  
Digestive Cells ◽  
Green Hydra ◽  
Algal Symbionts ◽  
Two Systems

Algal cells grown in the green hydra Chlorohydra viridissima were shown to possess characteristic antigenic determinants not found in algae cultured in vitro. These antigenic determinants, including those localized on the algal cell surface, were shown to be responsible for the phagocytic recognition of potential algal symbionts by digestive cells of Chlorohydra. The results of this study indicate the existence of two systems governing phagocytosis in Chlorohydra, one specific for algal cells grown in hydra, another governing the uptake of other particles by the hydra digestive cells.

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