First, the team exposed D. vulgaris to their much-preferred oxygen-free environment. They then exposed the same group of cells to air and monitored them for several hours.
The foreign environment proved too much for many cells; they died due to a toxic accumulation of free radicals. But some cells with adequate stores of energy survived.
And for the first time, thanks to the high-sensitivity synchrotron infrared beamline, the scientists watched as the surviving cells unleashed a series of metabolic changes that enabled them to endure in the presence of oxygen, like a fish out of water.
"We monitored several molecules simultaneously in the same bacteria, and watched their metabolic response to stress and extreme conditions," says Holman. "We found that multiple chemical processes allow them to adapt."
The scientists studied D. vulgaris because the bacterium, which is among a class of bacteria that reduce sulfate, plays a critical role in many important geochemical processes such as element and nutrient cycling in soils. It also assists in bioremediation and may someday be used to aid energy production and carbon sequestration efforts.
D. vulgaris also intrigues scientists because it is an obligate anaerobe meaning it can't survive in the presence of oxygen yet it participates in many geochemical processes in which oxygen levels fluctuate. For example, it thrives in algae mats, which produce very high concentrations of oxygen during the day.
Scientists have puzzled over this riddle for years. They've studied the bacterium's gene expression, which provides valuable clues to how it adapts. But, as Holman explain
|Contact: Dan Krotz|
DOE/Lawrence Berkeley National Laboratory