Starvation-Survival in Haloarchaea.

Area of Science:

• Microbiology
• Geobiology
• Extremophile Research

Background:

• Long-term microbial persistence in ancient halite fluid inclusions is under investigation.
• Survival strategies of halophilic archaea under nutrient deprivation are poorly understood.
• Previous studies suggest ancient microorganisms can be revived from halite.

Purpose of the Study:

• To investigate the long-term survival strategies of halophilic archaea in fluid inclusions within ancient evaporites.
• To determine if glycerol from single-celled algae supports haloarchaeal survival in halite.
• To characterize morphological and population changes in haloarchaea under nutrient-limited conditions.

Main Methods:

• Laboratory experiments simulating nutrient-rich, nutrient-deprived, and glycerol-rich conditions for haloarchaea (Hbt. salinarum and Haloterrigena isolate DV582A-1).
• Monitoring of morphological changes (rod to cocci) and population dynamics over 56 days.
• Assessment of haloarchaeal growth and morphology when exposed to lysed and intact Dunaliella algae.

Main Results:

• Haloarchaea Hbt. salinarum and DV582A-1 exhibited significant morphological changes, converting from rods to small cocci within 56 days of nutrient deprivation.
• The timing and nature of starvation adaptations varied between species and populations.
• Exposure to Dunaliella algae resulted in size reduction and shape transition to cocci, mimicking starvation responses rather than nutrient-rich growth, indicating glycerol is not the primary survival nutrient.

Conclusions:

• Nutrient deprivation induces significant morphological changes in haloarchaea, potentially differentiating cells trapped with or without nutrients in ancient halite.
• Glycerol from Dunaliella is not the limiting factor for the extended survival of haloarchaea in halite fluid inclusions.
• The study provides the first reported timing of starvation strategies for Hbt. salinarum and DV582A-1.