Halotolerance Mechanisms in Debaryomyces Hansenii

Debaryomyces hansenii is renowned for its extraordinary capacity to thrive in environments containing up to 4 M sodium chloride, distinguishing it as one of the most halotolerant eukaryotic microorganisms. Core mechanisms underpinning this resilience include active extrusion of sodium via plasma‐membrane Na+/H+ antiporters and regulation of intracellular ion balance through specialised cation transporters. Concurrently, the high‐osmolarity glycerol (HOG) signalling cascade orchestrates rapid accumulation of glycerol and other compatible solutes to counterbalance external osmotic pressure. Adaptations of membrane lipid composition reduce permeability and maintain fluidity under saline stress, while transient membrane depolarisation further limits uncontrolled ion influx. At the mitochondrial level, engagement of an alternative oxidase pathway mitigates reactive oxygen species formation during abrupt transitions to hyper‐osmotic conditions. A suite of antioxidant proteins, including alkyl hydroperoxide reductases, provides additional defence against oxidative damage. Collectively, these interlinked systems enable D. hansenii to adjust its physiology dynamically, making it an attractive platform for industrial bioprocesses that exploit saline feedstocks or require robust stress tolerance.

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Halotolerance Mechanisms in Debaryomyces Hansenii publication trend

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Technical terms

Compatible solute: A small organic molecule (e.g. glycerol) accumulated intracellularly to balance external osmotic pressure without interfering with cellular processes.

High‐osmolarity glycerol (HOG) pathway: A conserved mitogen‐activated protein kinase cascade that senses osmotic stress and regulates osmolyte synthesis.

Na+/H+ antiporter: A membrane protein that exchanges intracellular sodium for extracellular protons to maintain ion homeostasis.

Alternative oxidase: A mitochondrial enzyme that bypasses the cytochrome pathway to reduce reactive oxygen species generation under stress.

Membrane depolarisation: A change in the electrical potential across the plasma membrane that can modulate ion flux and permeability.

References

1. Open (non-sterile) cultivations of Debaryomyces hansenii for recombinant protein production combining industrial side-streams with high salt content. New Biotechnology (2023).
2. Hyper-Osmotic Stress Elicits Membrane Depolarization and Decreased Permeability in Halotolerant Marine Debaryomyces hansenii Strains and in Saccharomyces cerevisiae. Frontiers in Microbiology (2019).
3. Debaryomyces hansenii: an old acquaintance for a fresh start in the era of the green biotechnology. World Journal of Microbiology and Biotechnology (2022).
4. High Osmolarity Environments Activate the Mitochondrial Alternative Oxidase in Debaryomyces Hansenii. PLOS ONE (2017).
5. Characterization of a salt-induced DhAHP, a gene coding for alkyl hydroperoxide reductase, from the extremely halophilic yeast Debaryomyces hansenii. BMC Microbiology (2009).
6. Efficient PCR‐based gene targeting in isolates of the nonconventional yeast Debaryomyces hansenii. Yeast (2023).