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Limits of Life in Hostile Environments: No Barriers to Biosphere Function?

Summary

This research challenges our understanding of how microorganisms survive in extremely dry environments. The scientists discovered that certain fungi can grow in conditions previously thought impossible, not because of water availability itself, but due to the chemical nature of their environment. This has important real-world implications: • Could help develop better strategies for preventing food spoilage • May lead to new approaches for farming in drought-prone regions • Could improve our understanding of how life might survive on other planets • May help in developing new industrial processes that work in extreme conditions • Could assist in developing solutions for ecosystem restoration in desertified areas

Background

Environments hostile to life are characterized by reduced microbial activity resulting in poor soil and plant health, low biomass and biodiversity, and weak ecosystem development. While water activity (aw) is thought to primarily constrain the functional biosphere, the mechanisms behind this are not fully understood.

Objective

To investigate whether water activity per se limits cellular function in xerophilic fungi at extremely low water activities (≤0.72 aw), and to examine the role of chaotropic activity in determining their biotic window.

Results

The study found that for xerophilic fungi at aw values ≤0.72, water activity itself did not limit cellular function. Rather, chaotropic activity determined their biotic window. By adding compounds that reduced net chaotropicity, mycelial growth was achieved at water activities as low as 0.647, below previously recorded limits. Some fungi grew optimally under chaotropic conditions, providing evidence for a new class of extremophilic microbes termed ‘chaophiles’.

Conclusion

The research demonstrates that water activity is not always the defining parameter limiting microbial activity in high-solute environments. Rather, the net effect of chaotropic and kosmotropic activities can determine cellular function limits. This finding has implications for understanding microbial survival in hostile environments and could lead to enhanced biotechnological processes and increased productivity of agricultural systems in arid regions.
  • Published in:Environmental Microbiology,
  • Study Type:Laboratory Research,
  • Source: 10.1111/j.1462-2920.2009.02079.x
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