Researchers at MIT have recently made a significant discovery regarding the role of Prochlorococcus marinus, a tiny photosynthesizing organism in the ocean, in carbon cycling and microbial health. According to a report by MIT News, the team has found that Prochlorococcus, the most abundant photosynthesizing organism on Earth, engages in a process known as cross-feeding by releasing DNA building blocks that other marine microbes then utilize.
Specifically, these microbes shed purines and pyrimidines, the components of DNA, into their surroundings. At night, the processes seem to quickly ramp up, with bacteria such as SAR11, one of the most abundant in the ocean, taking to slow down their metabolism, effectively "recharging" for the next cycle. This interplay is thought to contribute to the sustainable growth of various ocean microrganisms, influencing the ocean's rhythms and stability, as per MIT News.
"The relationship between the two most abundant groups of microbes in ocean ecosystems has intrigued oceanographers for years," Sallie "Penny" Chisholm, a co-author of the study and MIT Institute Professor, told MIT News. "Now we have a glimpse of the finely tuned choreography that contributes to their growth and stability across vast regions of the oceans."
The scientists approached their research with emphasis on how these exchanges impact the complex marine carbon cycle. As Prochlorococcus and SAR11 are widespread in the surface oceans, the transfer of molecules could be one of the key interactions sustaining this global network. "By looking at the details and diversity of cross-feeding processes, we can start to unearth important forces that are shaping the carbon cycle," lead author Rogier Braakman, a research scientist at MIT’s Department of Earth, Atmospheric and Planetary Sciences, stated.
The study's findings also revealed that environmental conditions strongly influence how SAR11 bacteria utilize purine, based on a comprehensive meta-genomic analysis linking geographical and environmental data to those microbes’ genetics. When nitrogen is scarce in seawater, SAR11 bacteria consume purine primarily for its nitrogen. Conversely, if nitrogen is abundant, they break down purine for its carbon or energy. This could mean that Prochlorococcus is playing a larger, perhaps orchestral role in the function of the ocean's daily biological processes, with implications on how the entire ecosystem is regulated.
The research, which was supported by the Simons Foundation and the National Science Foundation, invites further investigation into the complex interactions that underpin not only marine life but also the broader environmental systems that govern our planet.
