Scientists Uncover Secrets Of Biological Soil Crust Microbes
June 14, 2013

Scientists Uncover Secrets Of Biological Soil Crust Microbes

Brett Smith for — Your Universe Online

A new study from the Lawrence Berkeley National Laboratory in Berkeley, California has found the biological soil crust (BSC) layer of a desert contains microbes that lie in wait for the ideal conditions to begin metabolic activity.

“We found a way to measure from start to finish in real unaltered samples the molecular events behind the response of cyanobacterium to wetting and drying in a desert BSC,” said Aindrila Mukhopadhyay, a biologist at the Berkeley Lab. “Not only did we get a good view of the genetic machinery that wakes the microbes up, but we also got a good sense of what constitutes a healthy BSC.”

The study, which was published in the journal of the International Society for Microbial Ecology, could have major implications for carbon cycling models and land management strategies.

Working with the researchers from Arizona State University, the Berkeley Lab team collected pie-sized samples of soil crust from the cold desert near Moab, Utah. These unmolested samples were subjected to wetting and drying cycles designed to model natural conditions over a six-day period. Throughout the six days, the researchers performed genomic analyses and biochemical surveys aimed at identifying microbial activity.

“Simulated weather conditions and sampling in a temporal manner over the six day experimental period allowed us to track key transcriptional and metabolic responses as they occurred,” Mukhopadhyay said.

“We found that within three minutes after wetting began, metabolic processes in the dormant microbial cells came alive,” she continued. “Within one hour, photosynthesis began, accompanied by carbon dioxide up-take. During this time we saw specific genes get turned on/off and specific gene expressions be elevated or depressed.”

The researchers found after the wetting cycle ended and the dehydration of the soil resumed, the mechanisms generated by exposure to water were reversed, suggesting the microbes were preparing to re-enter their dormancy phase.

“These BSC microbes are highly attuned to their environment and they respond very quickly to changes,” Mukhopadhyay said. “Their responses, however, are highly sensitive to physical disturbances and alterations in temperature.”

In the study, the researchers said their findings could be used to predict the impacts of climate or land-use change on this type of soil system and could help in the development of management strategies for arid regions.

“BSC systems represent the world´s largest biofilms, and the demise of such systems could release carbon, and probably more importantly, dust into the atmosphere,” said Trent Northen, a chemist with Berkeley Lab. “Restoring or protecting BSCs through changes in land-use could help pull carbon out of the atmosphere and reduce dust.”

Mukhopadhyay noted the findings could also provide knowledge of the carbon cycle, potentially improving the accuracy of climate models.

“In most climate models there is little or no accounting for the carbon fixed by soil microbes,” she said. “BSC cyanobacteria are the photosynthetic organism for deserts and understanding their role in the carbon-cycle will help fill in current climate model gaps. This should help improve the accuracy of these models.”