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Characterization of the decline and recovery of heat-treated Scenedesmus vacuolatus

View Article: PubMed Central

ABSTRACT

Background: To find out how algal cells cope with and recover from heat stress, the small vegetative cells of the synchronous Scenedesmus vacuolatus culture were subjected to a heat pretreatment (46.5°C for 1 h) followed by dark recultivation. The changes in physiological activities and morphology of Scenedesmus cells were continuously monitored throughout the course of decline and recovery.

Results: It was found that the heat treatment, though completely inhibited photosynthesis, did not kill Scenedesmus cells. These cells, during dark recultivation, could make a fast repair and regained the ability of proliferation. We suggest that they entered a ‘stand-by’ state, which was characterized by condensed chromatin, partially functional but morphologically altered chloroplasts, disappeared vacuoles, slightly shrunk protoplast and intact plasma membranes. These stressed cells, on the surface, seemingly were undergoing some kind of disintegration, could readily and quickly return to normal cells upon illumination. Cell death occurred only after a long period of darkness (>48 h).

Conclusions: Our results suggest that the recovery of algal cells from stress damage may actually proceed in two steps. The middle “stand-by’ stage normally is gone through too rapidly to be detected unless cells are kept in the dark.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-3) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus

The variation of the ability of cell proliferation. The relative numbers of green colonies formed from seeded cells that had either been heat-treated (○) or not been treated (●) are plotted as functions of the time of dark cultivation. All the data are normalized with respect to the value of untreated cells at the beginning of dark cultivation. Each data point represents the mean ±SD of three independent measurements with two replicates each.
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Fig1: The variation of the ability of cell proliferation. The relative numbers of green colonies formed from seeded cells that had either been heat-treated (○) or not been treated (●) are plotted as functions of the time of dark cultivation. All the data are normalized with respect to the value of untreated cells at the beginning of dark cultivation. Each data point represents the mean ±SD of three independent measurements with two replicates each.

Mentions: The numbers of green colonies formed 14 days later on agar plates were used as a measure of cell proliferation ability. Figure 1 shows the relative numbers of green colonies of heat-treated and untreated cells as functions of the time of dark cultivation. All the data have been normalized with respect to the value of untreated cells at the beginning of dark cultivation (3,467±42). Untreated cells remained viable after 84 h of dark cultivation, indicating normal Scenedesmus cells could survive darkness for a considerable period of time. On the other hand, all of the cells lost the ability to form green colonies right after heat treatment. A small number of green colonies appeared on the plates containing the heat-stressed cells that had been recultured for 6 h. The number of colonies then increased rapidly with culture time. After 12 h, the number of green colonies formed out of seeded cells became comparable with that of untreated cells, indicating that the heat pretreatment did not kill the algae, but a period of time was needed to do the repairing. However, after 48 h, viability started to decline rapidly, and no colony could be found longer than 72 h, suggesting that no cell could survive long term darkness.Figure 1


Characterization of the decline and recovery of heat-treated Scenedesmus vacuolatus
The variation of the ability of cell proliferation. The relative numbers of green colonies formed from seeded cells that had either been heat-treated (○) or not been treated (●) are plotted as functions of the time of dark cultivation. All the data are normalized with respect to the value of untreated cells at the beginning of dark cultivation. Each data point represents the mean ±SD of three independent measurements with two replicates each.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5383920&req=5

Fig1: The variation of the ability of cell proliferation. The relative numbers of green colonies formed from seeded cells that had either been heat-treated (○) or not been treated (●) are plotted as functions of the time of dark cultivation. All the data are normalized with respect to the value of untreated cells at the beginning of dark cultivation. Each data point represents the mean ±SD of three independent measurements with two replicates each.
Mentions: The numbers of green colonies formed 14 days later on agar plates were used as a measure of cell proliferation ability. Figure 1 shows the relative numbers of green colonies of heat-treated and untreated cells as functions of the time of dark cultivation. All the data have been normalized with respect to the value of untreated cells at the beginning of dark cultivation (3,467±42). Untreated cells remained viable after 84 h of dark cultivation, indicating normal Scenedesmus cells could survive darkness for a considerable period of time. On the other hand, all of the cells lost the ability to form green colonies right after heat treatment. A small number of green colonies appeared on the plates containing the heat-stressed cells that had been recultured for 6 h. The number of colonies then increased rapidly with culture time. After 12 h, the number of green colonies formed out of seeded cells became comparable with that of untreated cells, indicating that the heat pretreatment did not kill the algae, but a period of time was needed to do the repairing. However, after 48 h, viability started to decline rapidly, and no colony could be found longer than 72 h, suggesting that no cell could survive long term darkness.Figure 1

View Article: PubMed Central

ABSTRACT

Background: To find out how algal cells cope with and recover from heat stress, the small vegetative cells of the synchronous Scenedesmus vacuolatus culture were subjected to a heat pretreatment (46.5°C for 1 h) followed by dark recultivation. The changes in physiological activities and morphology of Scenedesmus cells were continuously monitored throughout the course of decline and recovery.

Results: It was found that the heat treatment, though completely inhibited photosynthesis, did not kill Scenedesmus cells. These cells, during dark recultivation, could make a fast repair and regained the ability of proliferation. We suggest that they entered a ‘stand-by’ state, which was characterized by condensed chromatin, partially functional but morphologically altered chloroplasts, disappeared vacuoles, slightly shrunk protoplast and intact plasma membranes. These stressed cells, on the surface, seemingly were undergoing some kind of disintegration, could readily and quickly return to normal cells upon illumination. Cell death occurred only after a long period of darkness (>48 h).

Conclusions: Our results suggest that the recovery of algal cells from stress damage may actually proceed in two steps. The middle “stand-by’ stage normally is gone through too rapidly to be detected unless cells are kept in the dark.

Electronic supplementary material: The online version of this article (doi:10.1186/1999-3110-54-3) contains supplementary material, which is available to authorized users.

No MeSH data available.


Related in: MedlinePlus