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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 before desiccation. (A–C) Culture grown under optimal conditions, viewed by light microscopy (A), stained with SYTOX Green (B), and CTC (C) fluorescent dyes; injured cells are marked with arrows. (D–F) Culture, kept at low temperature, viewed by light microscopy (D), stained with SYTOX Green (E), and CTC (F); necridic (dead) cells are SYTOX Green-positive and CTC-negative (asterisks); the injured cells are both SYTOX Green and CTC-positive (arrows). (G–I) Nitrogen-starved culture viewed by light microscopy (G), stained with SYTOX Green (H), and CTC (I); dead (in this case, decayed) cells are marked with asterisks. Scale bars are 20 μm.
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Figure 2: Microcoleus vaginatus 858 CCALA before desiccation. (A–C) Culture grown under optimal conditions, viewed by light microscopy (A), stained with SYTOX Green (B), and CTC (C) fluorescent dyes; injured cells are marked with arrows. (D–F) Culture, kept at low temperature, viewed by light microscopy (D), stained with SYTOX Green (E), and CTC (F); necridic (dead) cells are SYTOX Green-positive and CTC-negative (asterisks); the injured cells are both SYTOX Green and CTC-positive (arrows). (G–I) Nitrogen-starved culture viewed by light microscopy (G), stained with SYTOX Green (H), and CTC (I); dead (in this case, decayed) cells are marked with asterisks. Scale bars are 20 μm.

Mentions: Under optimal conditions, the cells were uniform in size and morphology, had an intense blue–green color and fluorescence of phycobiliproteins, well-pronounced thylakoids, lacked cell inclusions, and were arranged in long filaments (Figure 2A). The viability of these cells was confirmed by the lack of SYTOX Green staining (Figure 2B) and the accumulation of numerous small CTC-formazan deposits within each cell (Figure 2C). The cultures had a low percentage of dead (0.9–4.6%) and injured cells (0–2%) in different replicates/strains (Figure 3A). Most of the injured and dead cells occurred at the polar ends of filaments, possibly because of mechanical disruption of filaments during the staining procedure (Figure 2B).


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

Tashyreva D, Elster J - Front Microbiol (2015)

Microcoleus vaginatus 858 CCALA before desiccation. (A–C) Culture grown under optimal conditions, viewed by light microscopy (A), stained with SYTOX Green (B), and CTC (C) fluorescent dyes; injured cells are marked with arrows. (D–F) Culture, kept at low temperature, viewed by light microscopy (D), stained with SYTOX Green (E), and CTC (F); necridic (dead) cells are SYTOX Green-positive and CTC-negative (asterisks); the injured cells are both SYTOX Green and CTC-positive (arrows). (G–I) Nitrogen-starved culture viewed by light microscopy (G), stained with SYTOX Green (H), and CTC (I); dead (in this case, decayed) cells are marked with asterisks. Scale bars are 20 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Microcoleus vaginatus 858 CCALA before desiccation. (A–C) Culture grown under optimal conditions, viewed by light microscopy (A), stained with SYTOX Green (B), and CTC (C) fluorescent dyes; injured cells are marked with arrows. (D–F) Culture, kept at low temperature, viewed by light microscopy (D), stained with SYTOX Green (E), and CTC (F); necridic (dead) cells are SYTOX Green-positive and CTC-negative (asterisks); the injured cells are both SYTOX Green and CTC-positive (arrows). (G–I) Nitrogen-starved culture viewed by light microscopy (G), stained with SYTOX Green (H), and CTC (I); dead (in this case, decayed) cells are marked with asterisks. Scale bars are 20 μm.
Mentions: Under optimal conditions, the cells were uniform in size and morphology, had an intense blue–green color and fluorescence of phycobiliproteins, well-pronounced thylakoids, lacked cell inclusions, and were arranged in long filaments (Figure 2A). The viability of these cells was confirmed by the lack of SYTOX Green staining (Figure 2B) and the accumulation of numerous small CTC-formazan deposits within each cell (Figure 2C). The cultures had a low percentage of dead (0.9–4.6%) and injured cells (0–2%) in different replicates/strains (Figure 3A). Most of the injured and dead cells occurred at the polar ends of filaments, possibly because of mechanical disruption of filaments during the staining procedure (Figure 2B).

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