Glycerin is produced by a number of organisms, from yeast to vertebrates, some of which use it as an osmoprotectant, a molecule that prevents dangerous water loss in salty environments, while others use it as an antifreeze. Scientists have found that two species of unicellular green algae Chlamydomonas from Antarctica, called UWO241 and ICE-MDV, produce high levels of glycerol to protect them from osmotic water loss and possibly frostbite as well. Both algae synthesize glycerol using enzymes encoded by multiple copies of a recently discovered family of ancient genes. The results of the study, published in the journal Frontiers in Plant Science, illustrate the importance of adaptation, which allows organisms to not only survive but also thrive in extreme habitats.
The researchers collected both Chlamydomonas species at depths of 13 to 17 m, in an area with a steep salinity gradient, Lake Bonnie, a permanently ice-covered lake in the McMurdo Dry Valleys in Victoria Land, Antarctica. They have previously shown that both species are remarkably adapted to their extreme habitats, with photosynthetic machinery adapted to cold, saline and poor light, new proteins, thinner cell membranes that function at low temperatures, and ice-binding proteins that protect them from damage during freezing and thawing.
Our common goal is to understand how microorganisms survive in extreme environmental conditions. The Chlamydomonas species from Lake Bonnie are well-suited for such exploration because they are prone to many extreme conditions, including low light, low temperature, oxidative stress, and high salinity. The results presented are the first to show that microbial production of glycerol, which is well known in warm and salty environments, is also important in polar regions.
Dr. James Raymond, Associate Professor of Research at the University of Nevada School of Life Sciences
UWO241 and ICE-MDV carry three and five copies of a family of genes that synthesize glycerol in remote temperate algae. In the laboratory, UWO241 steadily increases the intracellular concentration of glycerol more than fourfold as the salt concentration in the medium increases from 400 to 1300 mM NaCl, which is approximately 0.8-2.5 times the salinity of seawater. They also demonstrate a parallel increase in DNA transcription into RNA of one of the gene copies, which strongly suggests that this gene family is also necessary and sufficient for glycerol synthesis in Chlamydomonas from Lake Bonnie.
A phylogenetic “family tree” based on protein sequence similarity shows that this gene family is ancient, possibly dating back to the origin of eukaryotic organisms more than a billion years ago, while multiple copies within each species are the result of recent gene duplications. discrepancy over time. These proteins contain three regions: a label that directs it to the chloroplast (the site of photosynthesis), a domain that converts the dihydroxyacetone phosphate molecule to glycerol-3-phosphate, and another domain that converts this intermediate to glycerol.
Scientists emphasize that glycerin is the main, but probably not the only osmoprotector in Chlamydomonas from Lake Bonnie: an increase in intracellular sugar and amino acids can also help maintain osmotic balance. Chlamydomonas can also produce glycerol in additional pathways, for example, by breaking down triglycerides.
Recent discoveries of the ability of microorganisms to survive in extreme environmental conditions are already having a big impact on current ideas about the possibility of life on other bodies in the solar system, where cold, salty bodies of water and even oceans seem to be in abundance, scientists conclude.