… like many scientists who study the Earth’s history, they dream of traveling back in time. But rather than wanting to travel back to the popular age of dinosaurs, they want to travel back to the Precambrian — a pivotal period which spanned from about 4.5 to 0.54 billion years ago.
The Precambrian fascinates Macalady. “The evolutionary success of single-celled microbes during the Precambrian brought the Earth to life and set the stage for the evolution of multi-cellular organisms that thrive today,” she says, adding that during the Precambrian microorganisms evolved the ability to produce oxygen from water through photosynthesis, a development that eventually led to the irreversible oxygenation of the Earth’s surface.
But because microorganisms leave poor fossil records, Macalady doesn’t use the fossil record to study the Earth’s oxygen revolution and the evolution of microbes. Instead, she studies these phenomena by analyzing modern microbial examples from Earth’s anoxic (oxygen-free), dark regions. However, these organisms are rare and difficult to access, found only underwater or in deep, dark underground environments (or combinations of the two) where stagnant water or unusual chemical conditions prevent oxygen from penetrating.
So how does Macalady manage to access such remote dangerous environments? By collaborating with expert cavers and cave divers who guide her and her colleagues to locations that would otherwise be beyond their reach and sometimes collect samples of microbial communities on her behalf.
So far, with funding from the National Science Foundation and NASA, Macalady has managed research collaborations between scientists and caving experts in dark, anoxic environments in Italy, Mexico, Florida and the Bahamas. …
Macalady’s post-doc, Sharmishtha Dattagupta, identified a new animal-microbe relationship (or symbiosis) in the Frasassi cave system that is based on chemical energy. Such symbiosis, which is common around hydrothermal vents on the sea floor that spew hot water, had not previously been known to occur outside of the oceans.
In addition, Italian cave divers discovered a slow-growing, anaerobic slime in the Frasassi cave waters; this slime contains large populations of cells that produce energy through novel methods that Macalady’s research team is currently struggling to understand. …