Feast or Famine: UM Bio Station Director Helps Shed Light on Microbe Evolution

March 04, 2020

FLBS director Jim Elser and research technician Laura Steger harvest samples of water for chemical analysis during a study in the Cuatro Ciénegas Basin of Mexico.MISSOULA – The director of the University of Montana’s Flathead Lake Biological Station recently joined a team of international scientists uncovering the evolutionary secrets of microorganisms existing in otherworldly environments.

Jim Elser and scientists from the J. Craig Venter Institute, Arizona State University, the United States Department of Agriculture and Universidad Nacional Autónoma de México wanted to determine how organisms evolve on Earth to cope with “feast or famine” scenarios. The results could help in understanding the possibilities for life on other worlds.

The researchers looked at how fundamental features of an organism’s genome drive trade-offs in its ability to persist in a nutrient-poor environment versus its ability to take advantage of nutrient pulses.

Elser, a senior author on the study, said it may be the first to identify and confirm that a microbe’s responses to the amount of nutrients in an ecosystem are due to its fundamental genome-wide traits, regardless of the species.

 “This study is unique and powerful,” Elser said. “It takes ideas from the ecological study of large organisms and applies them to microbial communities in a whole-ecosystem experiment.”

Researchers conducted the study in a shallow pond in the Cuatro Ciénegas Basin of Mexico – an area so poor in nutrients that many of its ecosystems are dominated by microorganisms descended from ancient marine ancestry.

This absence of nutrients combined with the microorganisms at play made the Cuatro Ciénegas Basin an ideal choice for the researchers, who are working to understand how life may have existed on other planets in our solar system. The ecosystems in the region are believed to be similar to ecosystems from early Earth and, potentially, the past environments of Mars as the planet lost its surface water.

From a physiological standpoint, microorganisms are incredibly diverse. Elser said they possess vastly different genomic features and mechanisms they use to persist and reproduce. These features form their life strategies and help determine the microorganisms’ population dynamics and distributions in the environment.

Going into the basin, the researchers hypothesized that microorganisms found in low-nutrient environments would, out of necessity, rely on low-resource strategies for the replication of their DNA, transcription of RNA and translation of protein. The successful microorganisms of high-nutrient environments, on the other hand, are those that use resource-intensive strategies.

Elser and his fellow researchers began by installing mesocosms, or miniature ecosystems, to create a control group. They then added a solution rich in nitrogen and phosphorus – the main ingredients of fertilizers – to the pond itself and observed how the nutrient-rich feast affected the pond’s microbial community.

For the next 32 days, the researchers conducted field monitoring, collected samples and analyzed water chemistry. Whole mixed microbial communities from both fertilized and unfertilized conditions were collected and examined for changes in response to the additional nutrients, based on the microorganisms’ ability to process biochemical information within their cells.

In a paper published in the journal eLIFE, the scientists reported that their hypothesis had been correct: A suite of genomic traits affecting the rates and costs of biochemical information processing were responsible for which species did best under the experimental “feast” they applied.

This means, no matter where they are located or which particular taxa are involved, microorganisms have information-processing machinery that is fine-tuned to the key resources provided to them from their surrounding environment.

To put it another way: There are rules of life for “feast and famine” that should be generally applicable to life on Earth and, just maybe, beyond.

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Contact: Jim Elser, director, Flathead Lake Biological Station, 406-872-4500, jim.elser@flbs.umt.edu; Ian Withrow, FLBS media/information specialist, 406-872-4544, ian.withrow@flbs.umt.edu.