Limits...
Effect of nitrogen starvation on desiccation tolerance of Arctic Microcoleus strains (cyanobacteria).

Tashyreva D, Elster J - Front Microbiol (2015)

Bottom Line: Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying.However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0-15% of cells to survive, while 39.8-65.9% of cells remained alive and intact after nitrogen starvation.Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation).

View Article: PubMed Central - PubMed

Affiliation: Centre for Polar Ecology, Faculty of Science, University of South Bohemia České Budějovice, Czech Republic ; Department of Botany, Faculty of Science, University of South Bohemia České Budějovice, Czech Republic.

ABSTRACT
Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying. We have discovered that three Microcoleus strains, isolated from terrestrial habitats of the High Arctic, survived extensive dehydration (to 0.23 g water g(-1) dry mass), but did not tolerate complete desiccation (to 0.03 g water g(-1) dry mass) regardless of pre-desiccation treatments. However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0-15% of cells to survive, while 39.8-65.9% of cells remained alive and intact after nitrogen starvation. Unlike Nostoc, which co-exists with Microcoleus in Arctic terrestrial habitats, Microcoleus strains are not truly anhydrobiotic and do not possess constitutive desiccation tolerance. Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation).

No MeSH data available.


Related in: MedlinePlus

Microcoleus vaginatus 858 CCALA after rehydration from complete desiccation, viewed by light microscopy. Cultures grown under optimal conditions (A), and kept at low temperatures (B), both containing filaments disintegrated into single cells; nitrogen-starved culture (C) with filaments enclosed in sheaths. Scale bars are 20 μm.
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Figure 4: Microcoleus vaginatus 858 CCALA after rehydration from complete desiccation, viewed by light microscopy. Cultures grown under optimal conditions (A), and kept at low temperatures (B), both containing filaments disintegrated into single cells; nitrogen-starved culture (C) with filaments enclosed in sheaths. Scale bars are 20 μm.

Mentions: Samples that underwent a complete drying regime appeared dry after a few minutes under the stream of air. The samples contained 0.03 ± 0.001 g water g-1 dry mass (mean ± SD) after drying over silica gel for 2 weeks. No live or viable but injured cells were detected upon rehydration in any of the replicates grown under optimal (control) conditions (Figure 3B). In samples treated with low temperature and nitrogen depletion prior to drying, no viable cells were observed either (Figure 3B), despite the presence of sheaths in the nitrogen starved cultures (Figure 4C). In all treatments/replicates, the filaments started to disintegrate into single cells a short time after rehydration (usually within 1 h) followed by their quick decay (Figures 4A,B). Fluorescence staining (data not shown) revealed that all the cells were CTC-negative and SYTOX Green-positive, indicating the absence of respiration and damage to their plasma membranes. A small number of cells were both SYTOX Green and DAPI-negative, which indicated deterioration of intracellular components, including nucleoids. This staining pattern corresponded to the category of injured and inactive, or dead cells. The growth test showed consistent results – no growth was detected after 5 weeks of cultivation, and the biomass used as inoculum underwent lysis. No statistical analysis was applied to this group.


Effect of nitrogen starvation on desiccation tolerance of Arctic Microcoleus strains (cyanobacteria).

Tashyreva D, Elster J - Front Microbiol (2015)

Microcoleus vaginatus 858 CCALA after rehydration from complete desiccation, viewed by light microscopy. Cultures grown under optimal conditions (A), and kept at low temperatures (B), both containing filaments disintegrated into single cells; nitrogen-starved culture (C) with filaments enclosed in sheaths. Scale bars are 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4389727&req=5

Figure 4: Microcoleus vaginatus 858 CCALA after rehydration from complete desiccation, viewed by light microscopy. Cultures grown under optimal conditions (A), and kept at low temperatures (B), both containing filaments disintegrated into single cells; nitrogen-starved culture (C) with filaments enclosed in sheaths. Scale bars are 20 μm.
Mentions: Samples that underwent a complete drying regime appeared dry after a few minutes under the stream of air. The samples contained 0.03 ± 0.001 g water g-1 dry mass (mean ± SD) after drying over silica gel for 2 weeks. No live or viable but injured cells were detected upon rehydration in any of the replicates grown under optimal (control) conditions (Figure 3B). In samples treated with low temperature and nitrogen depletion prior to drying, no viable cells were observed either (Figure 3B), despite the presence of sheaths in the nitrogen starved cultures (Figure 4C). In all treatments/replicates, the filaments started to disintegrate into single cells a short time after rehydration (usually within 1 h) followed by their quick decay (Figures 4A,B). Fluorescence staining (data not shown) revealed that all the cells were CTC-negative and SYTOX Green-positive, indicating the absence of respiration and damage to their plasma membranes. A small number of cells were both SYTOX Green and DAPI-negative, which indicated deterioration of intracellular components, including nucleoids. This staining pattern corresponded to the category of injured and inactive, or dead cells. The growth test showed consistent results – no growth was detected after 5 weeks of cultivation, and the biomass used as inoculum underwent lysis. No statistical analysis was applied to this group.

Bottom Line: Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying.However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0-15% of cells to survive, while 39.8-65.9% of cells remained alive and intact after nitrogen starvation.Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation).

View Article: PubMed Central - PubMed

Affiliation: Centre for Polar Ecology, Faculty of Science, University of South Bohemia České Budějovice, Czech Republic ; Department of Botany, Faculty of Science, University of South Bohemia České Budějovice, Czech Republic.

ABSTRACT
Although desiccation tolerance of Microcoleus species is a well-known phenomenon, there is very little information about their limits of desiccation tolerance in terms of cellular water content, the survival rate of their cells, and the environmental factors inducing their resistance to drying. We have discovered that three Microcoleus strains, isolated from terrestrial habitats of the High Arctic, survived extensive dehydration (to 0.23 g water g(-1) dry mass), but did not tolerate complete desiccation (to 0.03 g water g(-1) dry mass) regardless of pre-desiccation treatments. However, these treatments were critical for the survival of incomplete desiccation: cultures grown under optimal conditions failed to survive even incomplete desiccation; a low temperature enabled only 0-15% of cells to survive, while 39.8-65.9% of cells remained alive and intact after nitrogen starvation. Unlike Nostoc, which co-exists with Microcoleus in Arctic terrestrial habitats, Microcoleus strains are not truly anhydrobiotic and do not possess constitutive desiccation tolerance. Instead, it seems that the survival strategy of Microcoleus in periodically dry habitats involves avoidance of complete desiccation, but tolerance to milder desiccation stress, which is induced by suboptimal conditions (e.g., nitrogen starvation).

No MeSH data available.


Related in: MedlinePlus