A recent study reveals that Phaeocystis antarctica, an algae native to the Southern Ocean, can thrive without vitamin B12, challenging previous assumptions. This discovery, indicating the algae’s adaptability to B12 scarcity through a unique gene, has implications for Antarctic ecosystems, climate change models, and future research on algae’s survival strategies in changing environments.
Vitamin B12 deficiency can lead to serious and potentially deadly health issues in humans. Until now, the same deficiencies were thought to impact certain types of algae, as well. However, a recent study into the algae Phaeocystis antarctica (P. antarctica), exposed to various conditions of iron and vitamin B12, reveals that these organisms can survive without B12. This finding contradicts earlier predictions made through computerized genome sequence analysis, demonstrating the algae’s unexpected resilience to B12 deficiency.
The alga, native to the Southern Ocean, starts as a single-cell that can transform into millimeter-scale colonies. The research was published in PNAS and conducted by MITMIT is an acronym for the Massachusetts Institute of Technology. It is a prestigious private research university in Cambridge, Massachusetts that was founded in 1861. It is organized into five Schools: architecture and planning; engineering; humanities, arts, and social sciences; management; and science. MIT's impact includes many scientific breakthroughs and technological advances. Their stated goal is to make a better world through education, research, and innovation.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>MIT, WHOI, J.C. Venter Institute, and Scripps Institution of Oceanography (UCSD). It found that unlike other keystone polar phytoplankton, P. antarctica can survive with or without vitamin B12.
“Vitamin B12 is really important to the algae’s metabolism because it allows them to make a key amino acidAny substance that when dissolved in water, gives a pH less than 7.0, or donates a hydrogen ion.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>acid more efficiently,” said Makoto Saito, one of the study’s co-authors and senior scientist at the Woods Hole Oceanographic Institution (WHOI). “When you can’t get vitamin B12, life has ways to make those amino acids<div class="cell text-container large-6 small-order-0 large-order-1">
<div class="text-wrapper"><br />Amino acids are a set of organic compounds used to build proteins. There are about 500 naturally occurring known amino acids, though only 20 appear in the genetic code. Proteins consist of one or more chains of amino acids called polypeptides. The sequence of the amino acid chain causes the polypeptide to fold into a shape that is biologically active. The amino acid sequences of proteins are encoded in the genes. Nine proteinogenic amino acids are called "essential" for humans because they cannot be produced from other compounds by the human body and so must be taken in as food.<br /></div>
</div>” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>amino acids more slowly, causing them to grow slower as well. In this case, there’s two forms of the enzyme that makes the amino acid methionine, one needing B12, and one that is much slower, but doesn’t need B12. This means P. antarctica has the ability to adapt and survive with low B12 availability.”
Researchers conducting a study of P. Antarctica aboard the R/V Palmer in the Ross Sea. Credit: Makoto Saito
The MetE Gene Discovery
Researchers came to their conclusion by studying P. antarctica’s proteins in a lab culture, and also searching for key proteins in field samples. During their observation, they found the algae to have a B12-independent methionine synthase fusion protein (MetE). The MetE gene isn’t new, but was previously believed not to have been possessed by P. antarctica. MetE gives the algae the flexibility to adapt to low vitamin B12 availability.
“This study suggests that the reality is more complex. For most algae, maintaining a flexible metabolism for B12 is beneficial, given how scarce the vitamin’s supply is in seawater,” said Deepa Rao, lead researcher of the study and former MIT postdoc.“ Having this flexibility enables them to make essential amino acids, even when they can’t obtain enough of the vitamin from the environment. Implying that the classification of algae as B12-requiring or not might be too simplistic.”
An iceberg floats in Antarctica’s cold waters. Credit: Photo by Makoto Saito, Woods Hole Oceanographic Institution
Antarctica, which lives at the base of the food web, has been thought to be entirely controlled by iron nutrition. The discovery of the MetE gene also indicates vitamin B12 likely plays a factor. Because of its presence in P. antarctica, the adaptability of the algae gives it a potential advantage to bloom in the early austral spring when the bacteria that produce B12, are scarcer.
Future Research Directions
This discovery also has implications for climate change. The Southern Ocean, where P. antarctica is found, plays a significant role in the Earth’s carbon cycle. P. antarctica takes in the CO2 and releases oxygen through photosynthesisPhotosynthesis is how plants and some microorganisms use sunlight to synthesize carbohydrates from carbon dioxide and water.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>photosynthesis.
“As our global climate warms, there’s increasing amounts of iron entering the coastal Southern Ocean from melting glaciers,” Saito said. “Predicting what the next limiting thing after iron is important, and B12 appears to be one of them. Climate modelers want to know how much algae is growing in the ocean in order to get predictions right and they’ve parameterized iron, but haven’t included B12 in those models yet.”
“We are particularly interested in knowing more about the extent of strain level diversity. It will be interesting to see if B12 independent strains have a competitive advantage in a warmer Southern Ocean,” said co-author of the study Andy Allen, a joint professor at the J. Craig Venter Institute and the Scripps Institution of Oceanography at the University of California, San Diego. “Since there is a cost to B12 independence in terms of metabolic efficiency, an important question is whether or not strains that require B12 might become reliant on B12-producing bacteria.”
The discovery that P. antarctica has the ability to adapt to minimal vitamin B12 availability turns out to be true for many other speciesA species is a group of living organisms that share a set of common characteristics and are able to breed and produce fertile offspring. The concept of a species is important in biology as it is used to classify and organize the diversity of life. There are different ways to define a species, but the most widely accepted one is the biological species concept, which defines a species as a group of organisms that can interbreed and produce viable offspring in nature. This definition is widely used in evolutionary biology and ecology to identify and classify living organisms.” data-gt-translate-attributes=”[{“attribute”:”data-cmtooltip”, “format”:”html”}]” tabindex=”0″ role=”link”>species of algae that were also assumed to be strict B12 users previously. The findings from this study will pave the way for future research related to the carbon cycle and how different types of algae survive in the Southern Ocean’s cold and harsh environment.
Reference: “Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12–independent methionine synthase with widespread homologues” by Deepa Rao, Zoltán Füssy, Margaret M. Brisbin, Matthew R. McIlvin, Dawn M. Moran, Andrew E. Allen, Michael J. Follows and Mak A. Saito, 2 February 2024, Proceedings of the National Academy of Sciences.
DOI: 10.1073/pnas.2204075121
Source: SciTechDaily
