How life's forms modify and evolve the Earth II (Introduction)

by David Turell , Friday, February 16, 2024, 19:07 (279 days ago) @ David Turell

Microbiology of arctic seabeds:

https://phys.org/news/2024-02-bacteria-arctic-seabed-year.html

"The Arctic is cold and hostile to life, yet it is home to a large number of microorganisms whose activity has a significant impact on life on our planet. For example, bacteria in the seabed play a central role in processing the biomass of dead organisms, thereby transforming the contained carbon into hard-to-degrade substances that can remain stored for a long time.

"In addition to the cold, the unusual seasonality is a striking feature of polar habitats—day and night do not alternate every twelve hours, but rather the entire year fluctuates between midnight sun and polar night. This has a massive impact on local primary production, which is dependent on sunlight. In summer, tiny algae thrive in the seawater and also life on land flourishes. In winter, primary production largely comes to a standstill. Little research has been carried out into the extent to which the resulting strong fluctuations in the input of organic matter influence the bacteria in the seabed.

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"Surprisingly, the bacterial community in the seabed does not behave as expected considering the environmental conditions. "Although the input of organic material and its turnover rates fluctuate greatly over the course of the year, the composition of the bacterial community hardly changes at first glance," reports principal investigator Katrin Knittel.

"Bacteria in the seabed thus behave very differently to those in the water, where many of them exhibit a pronounced seasonality. "Benthic bacterial communities—i.e., those in the seabed—are very complex," Knittel adds. "That's what makes them so stable and robust, and it makes it very challenging for us to investigate their dynamics."

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"In winter, enzymes that break down a-glucans (e.g., glycogen) predominate. The a-glucans are intracellular storage compounds of heterotrophic bacteria, animals and fungi. They are also available throughout the rest of the year, but are then less important. In spring, however, there are more enzymes that break down b-glucans such as the algal component laminarin. Then there are so many b-glucans that some of them may be set aside as a storage for later in the year.

"'These enzymes reflect which algal components—especially algal sugars—are available to the bacteria in the different seasons," explains Knittel. "It's not so different to going to the farmers market here: While there are lots of different fresh fruit and vegetables available during the sunny season, at some point during the winter all that's left are the stored potatoes."

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"The bacteria in the seabed can hence utilize fresh material that sinks from the water column, particularly in spring and summer, such as the aforementioned laminarin. However, they can also consume material that is already present in the seabed or is produced there. This includes tasty treats such as mucin, but also tough chunks such as chitin. On these, the bacteria nibble all year round. This food source is particularly important in winter, when other input is scarce. Their long-term availability Their long-term availability stabilizes the bacterial community in the seabed.

"'These findings occur on very small scales, but they are important in a larger context: When the bacteria consume the algal sugars, they release carbon dioxide. And carbon dioxide is a very important greenhouse gas," Knittel notes. Thus, the tiny ocean inhabitants can have an influence on global processes."

Comment: we must continue to study microbiomes everywhere, since they are so influential.