Inverse Relationship Between Halophilic Growth and Cell Integrity Under Extremely Chaotropic Conditions.

Concentrated magnesium chloride brines are extreme environments that are inhospitable to life on Earth. The ionic strength of these brines significantly depresses water activity and concomitantly exerts significant chaotropic stress. Although these brines are largely considered sterile, the well-known preservative effects of magnesium chloride on certain biomolecules, such as DNA, confound life detection approaches and efforts to constrain precisely the habitable window of life on Earth.

Light cues drive community-wide transcriptional shifts in the hypersaline South Bay Salt Works.

The transition from day to night brings sweeping change to both environments and the organisms within them. Diel shifts in gene expression have been documented across all domains of life but remain understudied in microbial communities, particularly those in extreme environments where small changes may have rippling effects on resource availability. In hypersaline environments, many prominent taxa are photoheterotrophs that rely on organic carbon for growth but can also generate significant ATP via light-powered rhodopsins.

Biosignature Molecules Accumulate and Persist in Evaporitic Brines: Implications for Planetary Exploration.

The abundance of potentially habitable hypersaline environments in our solar system compels us to understand the impacts of high-salt matrices and brine dynamics on biosignature detection efforts. We identified and quantified organic compounds in brines from South Bay Salt Works (SBSW), where evapoconcentration of ocean water enables exploration of the impact of NaCl- and MgCl-dominated brines on the detection of potential biosignature molecules. In SBSW, organic biosignature abundance and distribution are likely influenced by evapoconcentration, osmolyte accumulation, and preservation effects.

Single-cell analysis in hypersaline brines predicts a water-activity limit of microbial anabolic activity.

Hypersaline brines provide excellent opportunities to study extreme microbial life. Here, we investigated anabolic activity in nearly 6000 individual cells from solar saltern sites with water activities () ranging from 0.982 to 0.

The Bioburden and Ionic Composition of Hypersaline Lake Ices: Novel Habitats on Earth and Their Astrobiological Implications.

We present thermophysical, biological, and chemical observations of ice and brine samples from five compositionally diverse hypersaline lakes in British Columbia's interior plateau. Possessing a spectrum of magnesium, sodium, sulfate, carbonate, and chloride salts, these low-temperature high-salinity lakes are analogs for planetary ice-brine environments, including the ice shells of Europa and Enceladus and ice-brine systems on Mars. As such, understanding the thermodynamics and biogeochemistry of these systems can provide insights into the evolution, habitability, and detectability of high-priority astrobiology targets.

Microbial diversity and activity in Southern California salterns and bitterns: analogues for remnant ocean worlds.

Concurrent osmotic and chaotropic stress make MgCl -rich brines extremely inhospitable environments. Understanding the limits of life in these brines is essential to the search for extraterrestrial life on contemporary and relict ocean worlds, like Mars, which could host similar environments. We sequenced environmental 16S rRNA genes and quantified microbial activity across a broad range of salinity and chaotropicity at a Mars-analogue salt harvesting facility in Southern California, where seawater is evaporated in a series of ponds ranging from kosmotropic NaCl brines to highly chaotropic MgCl brines.

Current state of athalassohaline deep-sea hypersaline anoxic basin research-recommendations for future work and relevance to astrobiology.

Deep-sea hypersaline anoxic basins (DHABs) are uniquely stratified polyextreme environments generally found in enclosed seas. These environments select for elusive and widely uncharacterized microbes that may be living below the currently recognized window of life on Earth. Still, there is strong evidence of highly specialized active microbial communities in the Kryos, Discovery, and Hephaestus basins located in the Eastern Mediterranean Sea; the only known athalassohaline DHABs.