Graduate Student & Post-Doc Seminar

Date: 

Thursday, March 14, 2019, 12:00pm to 1:00pm

Location: 

Faculty Lounge, Hoffman 4th floor

Speaker: Dr. Lewis Ward, Agouron Institute Postdoctoral Fellow

"Investigating the Early Earth through Comparative Biology: Case Studies from the Chloroflexi"

Abstract: The Chloroflexi are a metabolically diverse phylum of bacteria including filamentous anoxygenic phototrophs possessing the 3-hydroxypropionate bicycle for carbon fixation. It has been proposed that the Chloroflexi were among the earliest phototrophic bacteria, but the recent discovery of diverse new Chloroflexi—including aerobic and anaerobic heterotrophs, photoheterotrophs, and phototrophs using the Calvin cycle for carbon fixation—has suggested a more complicated history for this phylum. Here, we integrate multiple approaches for understanding the evolution of metabolism in the Chloroflexi, including recovery of novel lineages from metagenomic datasets, phylogenetic analysis of phototrophy, respiration, and carbon fixation genes, and cross- calibrated Bayesian relaxed molecular clock-based estimates for the age of Chloroflexi lineages. We demonstrate that the phototrophic Chloroflexi are relatively young, having evolved after the Great Oxygenation Event and the acquisition of aerobic respiration. The 3HP bicycle evolved within the Chloroflexi less than 1 billion years ago. Furthermore, phototrophy, respiration, and carbon fixation have been received by and exchanged within the Chloroflexi via horizontal gene transfer. Overall, our analyses reveal a complicated history of metabolic evolution in this phylum driven by horizontal gene transfer, with major radiations having occurred after the Great Oxygenation Event.

 

GSPD comprises scientific talks up to one hour in length by graduate students and post docs, but all are welcome to attend, including faculty and staff. Lunch will be provided. As always, please plan to bring reusable plates and cutlery to reduce waste.