All Spotlights » AWRI Student Research: Microbes Move to Optimize Underwater Light Harvest
Michael Snider on board the RV Storm.
Adam McMillan sampling cyano-
bacteria at the Alpena Library
Fountain, Alpena, MI.
Recently discovered submerged sinkholes in Lake Huron near Alpena, MI are inhabited by peculiar microbial life. These cyanobacteria live in low/no oxygen and high sulfur groundwater seeping out of Paleozoic marine evaporates in the region’s karst aquifers. Probably related to some of the first microbes that began the oxygenation of the biosphere, these microbes form a mat-like community, which allows them to optimize their light intake for photosynthesis through coordinated movement of their multicellular filaments. The Lake Huron sinkholes represent the only known refugia for these cyanobacteria in the Northern hemisphere; ice-covered Antarctic lakes are the only other location where they have been reported. The uniqueness of these cyanobacteria and our ability to maintain them in the lab makes them cool candidates for fascinating studies.
Before: A foil cutout allows a pattern
of light into a petri dish with randomly distributed cyanobacterial filaments.
After: Cyanbobacterial filaments
orient themselves in the light to
better optimize photosynthesis
in a roughly 1-hour period.
Working with their advisor Dr. Bopi Biddanda, Adam McMillan (D.J. Angus-Scientech Educational Foundation intern) and Michael Snider (AWRI graduate student), are studying the motility and photophysiology of these cyanobacteria, respectively. Adam has completed a series of phototaxis experiments that will help explain cell movement in response to light. He has found that the cyanobacteria are highly phototactic across great distances and quite fast relative to their size. At their max speeds, the sinkhole cyanobacteria cover the same body lengths per minute as a sprinting cheetah! Michael’s work has looked at the response of photosynthetic efficiency to changes in light intensity and quality. He has found that these cyanobacteria are highly capable of acclimating to rapid and extreme changes in light conditions over daily and seasonal solar cycles. Collectively, these findings may help explain why these mat builders are great at harvesting low and variable sunlight and reveal the secret of their survival in low-light, low-oxygen, high-sulfur modern day refugia.
Because of the enticing and long-enduring mystery of these cyanobacteria’s way of life and their extreme habitat, this project has been an exciting opportunity to collaborate with experts in different faculties and from multiple institutions. For example, we have been privileged to partner with the University of Michigan (UM), and the National Oceanic and Atmospheric Administration’s (NOAA) Great Lakes Environmental Laboratory and Thunder Bay National Marine Sanctuary. Partnering with UM on genomic studies of these ecosystems has revealed well-hidden secrets about their extremely low taxonomic diversity coupled to high functional diversity. NOAA’s dive team and research vessel assisted us in obtaining samples from the Lake Huron sinkhole. Bridging the gap between scientists’ needs and divers’ skill set for sampling many meters below the surface of the lake has been challenging and rewarding. Thus, this multidisciplinary project offers a rich field and lab learning experience for students.