Dispersal strategies stimulate marine microbial diversity

Trade-offs between the benefit of colonizing new particles and the risk of being wiped out by predators allow diverse populations of marine microbes to exist together, shows a study published today in eLife.

The findings help explain how a wide range of diverse bacteria and microbes coexist on floating particle rafts in the oceans.

Microbial foraging in uneven environments, where resources are fragmented into particles, plays a key role in natural environments. In oceans and freshwater systems, bacteria and microbes can interact with particle surfaces in different ways: some only colonize them for short periods of time, while others form stable colonies with long life spans. life.

Scientists have long been intrigued by the greater-than-expected diversity of microscopic creatures in the oceans, a phenomenon called the “plankton paradox.” While researchers have begun to understand the factors that sustain so many different types of plankton, many questions remain about the more abundant ocean microbes that live on floating particles.

“We wanted to investigate the role dispersal strategies play in the successful coexistence of different microbes living on the same set of particles,” says co-first author Ali Ebrahimi, who completed the study while a postdoctoral fellow. at the Ralph M. Parsons Laboratory for Environmental Science and Engineering, Massachusetts Institute of Technology (MIT), Cambridge, USA.

Ebrahimi and the team used mathematical modeling and computer simulations to test how different dispersal strategies can help marine microbes coexist in this way. They found that navigating the trade-offs between growth and survival differently can allow microbes to thrive together.

Their model showed that organisms that stay longer on a single particle have more opportunities to multiply. However, they are at a higher risk of being wiped out by a virus or other predator capable of engulfing whole particles. On the other hand, microbes that jump between particles more frequently have fewer opportunities to multiply, but also have a lower risk of facing a mass death event. The success of one strategy over another may depend on different environmental conditions.

“When the particle supply is high, microbes that quickly jump between them will be more likely to survive,” says co-first author Akshit Goyal, Physics of Living Systems Fellow in MIT’s Department of Physics. “But when the particles are harder to find, the bacteria that stick around will have an advantage.”

Additionally, the team found that coexistence can remain stable in the face of changing environmental conditions, such as particulate algal blooms, promoting growth and changing numbers of predators, promoting mortality. Together, these different factors greatly increase the likelihood that populations with diverse dispersal strategies can live together.

“Our work has focused on the link between dispersal and mortality in the ocean, but much more is happening in these environments,” Goyal concludes. “Future research could provide important new insights into how environmental changes might impact these tiny communities and, therefore, their larger marine ecosystem.”

Co-first authors Ebrahimi and Goyal worked on this study alongside lead author Otto Cordero, an associate professor in MIT’s Department of Civil and Environmental Engineering.

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