Departmental Advances in Geomicrobiology

Posted on 08.23.2015

Several department members reported advances in geomicrobial studies at the GSA meeting in Reno, Nevada, last November. Graduate student Qusheng Jin and Craig Bethke, professor of geology, announced a new, unified theory of microbial kinetics. Bruce Fouke, assistant professor of geology, announced new findings regarding microbial transport in hot springs.

Bethke has studied the rates at which microbial populations metabolize in the natural environment. That work has been limited by the lack of a general theory about those rates. Bethke and Jin have derived a rate law that is based on the internal mechanisms of microbial respiration. This rate law accounts for the thermodynamics of the metabolization process and the energy required to produce ATP. Bethke and Jin also take into account the abundance of microbes and the concentrations of substrate species and reaction products in solution.

"The growth of microbial populations can have profound effects on the chemistry of groundwater, from acid-mine drainage in the West to arsenic poisoning in Bangladesh," said Bethke. "The bulk of the world's microbial biomass operates by eating rocks - taking inorganic chemicals and using them to produce energy. By constructing quantitative models of that reaction process, we might find more effective solutions and control measures to groundwater problems."

In other microbial research, Fouke and post-doctoral fellow George Bonheyo have looked at the relationship of microbes to their environments and how they might travel between environments. Working at Mammoth Hot Springs in Yellowstone National Park, the team, which also includes microbiologist Abigail Salyers and students Beth Sanzenbacher and Janki Patel, has collected water, rock and air samples. They then used the polymerase chain reaction (PCR) technique on microbial 16Sr RNA to detect the presence and type of microbes. The next step is to determine where the microbes came from and how they got there.

"Hot springs are complex ecosystems of interacting microbes, geochemistry and mineralogy," says Bonheyo. "The source of the microbes, and the means by which they colonize new springs, has remained unknown."

Bonheyo points out, for example, that bacteria that exist at 73 degrees centigrade cannot simply travel across open land to another spring. This observation led him to wonder how bacteria travel.

The rapid precipitation of calcium carbonate in hot springs often results in shifting flows, the sealing off of some springs, and the eruption of new vents. Last year, the researchers got a chance to investigate five new springs that erupted at Angel Terrace, part of the Mammoth Hot Springs complex. The team did find bacteria in the new springs. They theorize that while some bacteria got there via the subterranean water system, others hitched a ride on the steam rising from surrounding springs.

"When we witnessed the birth of those new springs, the water flowing through the ground from the new springs initially was only 45 degrees centigrade," says Bonheyo. "And the only bacteria initially detected by PCR in the new spring waters were those that we normally find living in cooler sections of mature springs. But after about 18 hours, the temperature had risen to 73 degrees, where it has remained. And as the temperature rose, new bacteria were detected that are found only in the hotter regions of the mature springs."

Bonheyo suggests that this second group of bacteria that need warmer temperatures to survive probably traveled by steam from a mature spring, but further study is  needed to prove this conclusively.

This research was funded by a University of Illinois Critical Research Initiatives grant and the American Chemical Society Petroleum Research Fund.