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).
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机译：尽管Microcoleus种的脱水耐受性是众所周知的现象，但关于它们的脱水耐受性极限的信息很少，包括细胞含水量，其细胞的存活率以及诱导其抗干燥性的环境因素。我们发现，从北极高地陆地生境中分离出的三株Microcoleus菌株在大量脱水中存活下来（至0.23 g水g -1 干重），但不耐受完全干燥（至0.03 g水） g -1 干燥质量），无论是否进行干燥前处理。然而，这些处理对于不完全干燥的生存至关重要：在最佳条件下生长的培养物即使不完全干燥也无法生存。低温使仅0–15％的细胞得以存活，而39.8–65.9％的细胞在氮饥饿后仍存活并完好无损。与Nostoc在北极陆地栖息地中与Microcoleus共存的情况不同，Microcoleus菌株并不是真正的亲水生物，并且不具有组成型干燥耐受性。取而代之的是，Microcoleus在周期性干燥的栖息地中的生存策略似乎涉及避免完全干燥，但对次优条件（例如氮饥饿）诱导的更温和的干燥压力具有耐受性。
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