Vitamin B12 adaptability in Antarctic algae has implications for climate change, life in the Southern Ocean
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AN ICEBERG FLOATS IN ANTARCTICA’S COLD WATERS.
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CREDIT: PHOTO BY MAKOTO SAITO, ©WOODS HOLE OCEANOGRAPHIC INSTITUTION
Woods Hole, MA — Vitamin B12 deficiency in people can cause a slew of health problems and even become fatal. Until now, the same deficiencies were thought to impact certain types of algae, as well. A new study examined the algae Phaeocystis antarctica’s (P. antarctica) exposure to a matrix of iron and vitamin B12 conditions. Results show that this algae has the ability to survive without B12, something that computer analysis of genome sequences had incorrectly indicated.
The alga, native to the Southern Ocean, starts as a single-cell that can transform into millimeter scale colonies. The research published in PNAS, "Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12-independent methionine synthase with widespread homologues,” conducted by MIT, WHOI, J.C. Venter Institute, and Scripps Institution of Oceanography (UCSD), 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 and because it allows them to make a key amino 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 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 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”
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.
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 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 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.
Researchers conducting a study of P. Antarctica aboard the R/V Palmer in the Ross Sea.
CREDIT
(Photo courtesy: Makoto Saito)
JOURNAL
Proceedings of the National Academy of Sciences
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Flexible B12 ecophysiology of Phaeocystis antarctica due to a fusion B12–independent methionine synthase with widespread homologues
ARTICLE PUBLICATION DATE
5-Feb-2024
Small but mighty – study highlights the abundance and importance of the ocean’s tiniest inhabitants
Tiny plankton – measuring less than 20µm (or 0.02mm) in diameter – make up the majority of plankton in the ocean and play a critical role in the planet’s health, according to new research.
However, scientists say challenges in identifying them have led to them becoming a silent majority that is currently being overlooked when it comes to global ocean policy.
The study is one of the first to explore the abundance and importance of these tiny ocean inhabitants around the UK coastline, with the technology capable of monitoring them only having been introduced in around 2010.
However, that monitoring has shown that in some instances, 99.98% of plankton abundance – and 71% of plankton biomass – is derived from these tiny cells.
The research has also shown they can be impacted directly by changes in ocean temperatures and nutrients, in addition to other environmental shifts taking place as a result of climate change.
Published in the journal Ecological Indicators, the study involved a number of the UK’s leading plankton scientists – including experts from all three of the Marine Research Plymouth partners – and was carried out using cutting edge surveying and identification techniques.
Lead author Dr Abigail McQuatters-Gollop, Associate Professor of Marine Conservation at the University of Plymouth, said: “You hear of phrases like searching for a needle in a haystack, but this takes it to a whole new level. Identifying something that measures 0.02mm in the ocean is an immense challenge, but an increasingly important one at a time of huge environmental pressures. These plankton may be tinier than most people can realistically imagine, but they underpin the entire marine food web and play a critical role in producing the oxygen our planet needs. We need to take this silent majority more seriously.”
Larger plankton have been used for decades to monitor ecosystem productivity and biodiversity, but four UK plankton surveys – including the Marine Biological Association’s Continuous Plankton Recorder survey – have also sampled tiny plankton in the past 14 years.
The researchers involved in the current study used the results of those surveys, which focused on the English Channel and Scottish coast, to investigate six groups of tiny plankton including two groups of heterotrophic bacteria.
Doing that involved a combination of flow cytometry – a laser-based technique used to detect and analyse the chemical and physical characteristics of cells or particles – and light microscopes.
This provided evidence of the abundance of tiny plankton, with that data then being cross-referenced against known changes in environmental conditions to assess how they were being impacted.
As a result, the researchers have recommended that tiny plankton groups should be used to inform biodiversity indicators that meet policy obligations under the EU Marine Strategy Framework Directive (MSFD), (Oslo-Paris Convention) OSPAR strategies, and the UK Marine Strategy.
They have also called for long-term monitoring of tiny plankton across multiple sites to ensure that policy decisions are based on accurate local and global evidence.
Study co-lead Dr Rowena Stern, a CPR Research Fellow at the Marine Biological Association (MBA), added: “We have been able to connect these tiny plankton to meaningful indicators for policy use by measuring how human-driven environmental pressures affect the timing of their growth. This has only been possible by taking consistent, long-term measurements of these types of plankton.”
• The full study – McQuatters-Gollop et al: The silent majority: pico- and nanoplankton as ecosystem health indicators for marine policy – is published in Ecological Indicators, DOI: 10.1016/j.ecolind.2024.111650. It involved researchers from: the University of Plymouth; The Marine Biological Association (MBA); Plymouth Marine Laboratory; Environment Agency; Marine Scotland Science; Centre for Environment, Fisheries and Aquaculture Science (Cefas); Scottish Association for Marine Science.
JOURNAL
Ecological Indicators
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
The silent majority: pico- and nanoplankton as ecosystem health indicators for marine policy
ARTICLE PUBLICATION DATE
5-Feb-2024
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