UC San Diego

Known for its ecological importance as the most halophilic eukaryotic phototroph, Dunaliella is utilized for its salt tolerance in a variety of industrial applications. With rising temperatures and elevated salinity levels, Dunaliella has witnessed increased rates of mortality in the process of cultivation. To improve upon current growth conditions, this paper along with recent research has turned toward investigating algal-bacterial relationships. Through co-culture experiments in varying salinities and FT-ICR MS analysis, this paper aimed to understand the ecological associations between Dunaliella sp. 15-1 and eight different heterotrophic prokaryotes. The findings indicated significant enhancement in growth rates, especially at higher salinities for both the Halolamina (isolate 025) and Halorubrum (isolate 027) species co-cultured with Dunaliella. Further investigation of these two co-cultures through metabolomic analysis revealed an upregulation of biological pathways involved in membrane fluidity, osmoregulation through increased compatible solute concentrations and improved ion transport. These pathways are likely upregulated by the presence of heterotrophic prokaryotes and contribute to the improved growth and salinity tolerance of the microalgae, suggesting a mutualistic or commensalistic symbiotic relationship.