ECIMMEE Project: Microbial Social Networking: Coevolution of Bacteria and Algae in a Changing Ocean
Fossil fuel consumption is changing Earth’s climate at an unprecedented rate. Through their roles in primary production, the microbial loop, and the biological carbon pump, marine microbes are critical regulators of atmospheric CO2. The interplay between phytoplankton photosynthesis and bacterial decomposition will determine how much anthropogenic CO2 remains in the atmosphere vs. ocean sediments. Due to the importance of these processes, studies have focused on constraining their relative rates. Interpretations of these studies remain mechanistically simple; phytoplankton dynamics are generally modeled as simple negative ecological interactions, and bacteria are generally thought of as a poorly differentiated “black box” responsible for remineralizing phytoplankton-derived organic matter. Further, different phytoplankton species are collapsed into functional groups, and the impacts of genetic variation and rapid selection are ignored. Our results suggest such simplifications are problematic. We have shown that the response of the dominant phytoplankter Prochlorococcus to year 2100 CO2 concentrations changes dramatically depending on community context, ranging from strongly negative in co-culture with the heterotrophic bacterium Alteromonas to mildly positive in co-culture with its sister taxon Synechococcus. We have also shown that Prochlorococcus can adapt to future CO2 conditions within months, adopting a growth phenotype not observed in modern isolates. Finally, we have shown that Prochlorococcus and Synechococcus, usually assumed to be direct competitors, are capable of long-term coexistence stabilized by currently unknown “Black Queen” interactions. We suggest these evolutionary dynamics are widespread in marine microbial communities and propose experiments to constrain their strength and functional form. First, we will investigate the specificity and reproducibility of coevolution between different phytoplankton and the “helper’ bacterium Alteromonas. Second, we will measure the competitive fitness of Prochlorococcus cultures evolved at year 2100 CO2 in the laboratory vs. natural Prochlorococcus communities, and the role of coevolved helper bacteria in this interaction. Finally, we will explore the diversity of bacterial “contaminants” that are able to coexist long-term with cultured phytoplankton
Jeff Morris received his Ph.D. in microbiology from the University of Tennessee in 2011, where he studied the interactions between phytoplankton and algae under Dr. Erik Zinser. He then did a postdoc at Michigan State with Rich Lenski, where he developed the “Black Queen Hypothesis” to explain how reductive evolution can lead to ecological marketplace exchanges. As a professor at the University of Alabama at Birmingham, Morris continues to study the evolution and ecology of algal-bacterial interactions and microbial markets. He is also a champion of undergraduate education reform, especially the use of authentic practices and “real research” in teaching laboratories. Outside of the laboratory, he is a brewer, a guitarist, and a farmhand for his wife Laura’s community-supported agriculture operation.