Extreme extremophiles: from total dormancy to living (Introduction)

by David Turell , Friday, March 28, 2025, 16:23 (6 days ago) @ David Turell

From the Baltic's bottom sludge:

https://phys.org/news/2025-03-years-oxygen-baltic-sea-mud.html

"A research team led by the Leibniz Institute for Baltic Sea Research Warnemünde (IOW) was able to revive dormant stages of algae that sank to the bottom of the Baltic Sea almost 7,000 years ago. Despite thousands of years of inactivity in the sediment without light and oxygen, the investigated diatom species regained full viability.

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"Many organisms, from bacteria to mammals, can go into a kind of "sleep mode," known as dormancy, in order to survive periods of unfavorable environmental conditions.

"They switch to a state of reduced metabolic activity and often form special dormancy stages with robust protective structures and internally stored energy reserves. This also applies to phytoplankton, microscopically small plants that live in the water and photosynthesize. Their dormant stages sink to the bottom of water bodies, where they are covered by sediment over time and preserved under anoxic conditions.

"'Such deposits are like a time capsule containing valuable information about past ecosystems and the inhabiting biological communities, their population development and genetic changes," explains Sarah Bolius.

"The IOW phytoplankton expert is the first author of the study, in which sediment cores from the Baltic Sea were analyzed specifically for viable phytoplankton dormant cells from the past.

"'This approach bears the rather unusual name of 'resurrection ecology': Dormant stages that can be clearly assigned to specific periods of Baltic Sea history due to the clear stratification of the Baltic Sea sediment are to be brought back to life under favorable conditions, then they are genetically and physiologically characterized and compared with present-day phytoplankton populations," continues Bolius.

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"The team led by Bolius, which included IOW experts as well as researchers from the Universities of Rostock and Constance, examined sediment cores taken from 240 meters water depth in the Eastern Gotland Deep during an expedition with the research vessel Elisabeth Mann Borgese in 2021.

"In favorable nutrient and light conditions, viable algae could be awakened from dormancy from nine sediment samples and individual strains were isolated. The samples were taken from different sediment layers that represent a time span of around 7,000 years and thus the main climate phases of the Baltic Sea.

"The diatom species Skeletonema marinoi was the only phytoplankton species that was revived from all samples. It is very common in the Baltic Sea and typically occurs during the spring bloom. The oldest sample with viable cells of this species was dated to an age of 6,871 ± 140 years.

"'It is remarkable that the resurrected algae have not only survived 'just so,' but apparently have not lost any of their 'fitness,' i. e. their biological performance ability. They grow, divide and photosynthesize like their modern descendants," emphasizes Bolius.

"This even applies to the cells from the roughly 7000-year-old sediment layer, which proved to be stable during cultivation with an average growth rate of about 0.31 cell divisions per day—a value similar to the growth rates of modern-day S. marinoi strains, says Bolius.

"The measurement of photosynthetic performance also showed that even the oldest algae isolates can still actively produce oxygen—with average values of 184 micromoles of oxygen per milligram of chlorophyll per hour. "These are also values that are comparable to those of current representatives of this species," says Bolius.

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"'Our study also shows that we can directly trace genetic changes over many millennia—by analyzing living cells instead of just fossils or DNA traces," concludes Bolius."

Comment: these diatoms are very simple forms that can assume dormancy. It just shows how tough living cells can be. The hibernating bear is a different form of this.