Surviving salt fluctuations: stress and recovery in Halobacterium salinarum , an extreme halophilic Archaeon

Halophilic proteins subjected to below about 15% salt in vitro denature through misfolding, aggregation and/or precipitation. Halobacteria, however, have been detected in environments of fluctuating salinity such as coastal salterns and even around fresh water springs in the depths of the Dead Sea. In order to identify the underlying mechanisms of low salt survival, we explored the reactivation capacity of Halobacterium (Hbt) salinarum sub-populations after incubation in low salt media and recovery in physiological salt. Respiratory oxygen consumption was assessed in stressed cells and cell viability was estimated by Live/Dead staining and flow cytometry. In vivo neutron scattering experiments showed that the recovery of Hbt salinarum sub-populations exposed to severe low salt conditions is related to a rapid retrieval of functional molecular dynamics in the proteome. In the hypothesis that the observations on Hbt salinarum have wider relevance, they could be of key ecological significance for the dispersion of extremophiles when environmental fluctuations become severe.