What is life like at symbiosis institutes?

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Lutz Becks is professor of limnology in the Biology Department at the University of Konstanz and heads the University's Limnological Institute. He is now receiving around 1.8 million euros from the Gordon and Betty Moore Foundation to research the genetic and cellular mechanisms of symbiosis. His five-year research project entitled “Will you kindly cooperate?” Is funded as part of the investigator program of the “Symbiosis in Aquatic Systems Initiative”, which was launched in 2019 by the Gordon and Betty Moore Foundation. The initiative, endowed with a total of 140 million US dollars (around 130 million euros), researches the functioning and development of symbioses between microorganisms in salt and freshwater ecosystems.

Why do two individuals enter into a symbiotic relationship?

The term symbiosis in the broadest sense describes the coexistence of life forms that belong to two different species, but whose survival and reproduction depend on mutual interaction. “Symbioses have decisively shaped the development of life and diversity on earth,” says Becks. “This applies to plants as well as to the mitochondria in human cells. So we are talking about very basic mechanisms of life ”. He will not only investigate the reasons why two individuals combine to form an organism, but also investigate the question of which environmental conditions favor or hinder the formation of symbiotic forms of life.

“There are at least two ideas about why symbioses arise: One idea is that both partners benefit from it from the start. Another idea is that one partner takes advantage of the other and binds them to themselves in the long term, ”explains Becks. So far, research has provided evidence for both hypotheses, the probability of which Professor Becks will investigate as part of his new project with experimental evolution. “In order to be able to check probabilities, we have to examine a very large number of replicates,” says the scientist. “To do this, we need automated methods with which we can process and compare many samples simultaneously over long periods of time under constant conditions.” These include pipetting robots, but also automated imaging processes that monitor the changes that the evolution of symbioses at the cell level triggers, make visible.

Which environmental conditions lead to the formation of stable symbioses?

For the study, Becks used green algae of the species Chlorella as symbionts and paramecia of the species Paramecium bursaria as hosts. These two partners are particularly suitable as a model system because their interactions are comparable to one of the processes that once led to the evolution of green plants. In the experiments, the algae and paramecia are exposed to different environmental conditions. This allows Becks' team to understand the conditions under which symbioses develop. The decisive question for the scientist is whether the symbiont is transferred from the mother cell to the daughter cell, or whether the daughter cell itself can also accept new symbionts from the environment.

"We create different environments, expose our organisms to these conditions and let them grow over many generations," explains Becks. This method is called experimental evolution. One approach within the study is to add chloroviruses to the algae and paramecia, which infect the algae and thus influence the conditions for the evolution of a symbiosis. In the end, the scientists then compare whether certain properties, as in this case, symbioses have developed under one or the other condition.

According to the theory, the probability of the formation of stable symbioses is greater if the transfer of symbionts only takes place from the mother to the daughter cell. In long-term studies, this assumption can be checked by manipulating the environmental conditions. Accordingly, parts of the population are repeatedly exposed to new environmental conditions throughout the study. The changes that take place over time are closely monitored by taking individual individuals and examining them. “What we are particularly interested in is the question of how dependent the host and symbiont are on each other at different points in time during the experiment. We test this, among other things, by separating them again and seeing whether they continue to grow and reproduce, ”says Becks. At the same time, the scientists use genomic analyzes to examine whether and which genetic changes are taking place. "If you get to the point in between when a paramecium turns green that is actually not green - that is, it has taken in a symbiote - then that is a wonderful experience."

Fact overview:

  • The Constance limnologist Prof. Dr. Lutz Becks receives funding of around 1.8 million euros from the Gordon and Betty Moore Foundation.
  • His five-year project examines the genetic and cellular mechanisms of symbiosis as well as the environmental conditions that favor or hinder the formation of symbiotic life forms.
  • Funding amount: around 1.8 million euros.
  • Funding period: five years.

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