Disney’s "Frozen" princess, Elsa, isn’t the only one who can turn water to ice. The bacterium Pseudomonas syringae has the same capability.
Recently, Virginia Tech researchers found that Southwest Virginia’s Claytor Lake contains it.
The bacteria are not dangerous to humans, but some strains can cause plant disease on hosts such as tomatoes, beans, and wheat. The team is currently investigating whether strains that cause plant disease are found in Claytor Lake.
For the initial study, published in Frontiers of Microbiology on March 9, they sampled the lake in four locations during two seasons and at three depths.
“We were surprised to find that every sample of water we collected from the lake contained Pseudomonas syringae,” said David Schmale, a professor of plant pathology, physiology and weed science in the College of Agriculture and Life Sciences and a Fralin Life Science Institute affiliate. “Not only is the bacteria extremely abundant in the lake, but there is also a diverse population, with multiple strains.”
“The abundance of Pseudomonas syringae in Claytor Lake adds to the growing evidence that the use of creek, lake, and pond water for irrigation purposes can increase the risk of crop disease outbreaks caused by this bacterium,” said Boris Vinatzer, professor and interim head of plant pathology, physiology and weed science in the College of Agriculture and Life Sciences and Fralin Life Science Institute affiliate.
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Schmale and Vinatzer are also investigating the bacterium’s role in the water cycle, and how it evolved the proteins that allow it to freeze water as warm as -4 degrees Celsius (24.8 degrees Fahrenheit), compared with the -38 degrees Celsius (-36 degrees Fahrenheit) at which pure water freezes.
The researchers’ hypothesis is that the bacterium uses this freezing ability to move through the water cycle, aerosolizing from a water body through a wave crash or other churning of the water due to boating, water skiing, or human activities. From there, it can travel through the air and could become part of a cloud before it falls down to earth as rain or snow, and then aerosolizes again.
Having the ability to freeze water at a warmer temperature would give the bacterium an advantage in colder temperatures, allowing it to move around more quickly and out-compete other bacteria unable to perform this feat.
Renee Pietsch, a former biological sciences Ph.D. student at Virginia Tech, got the idea to investigate the bacterium’s abundance in Claytor Lake when she, Schmale, and Vinatzer noticed a large amount of the bacterium in the rain samples collected around Blacksburg.
“We wondered if some of the bacteria that we collected in rain could be coming from local water reservoirs, having traveled through the water cycle,” Schmale said. “Claytor Lake struck us as a good place to check.”
But the extreme abundance of the bacterium in the lake was a surprise to Pietsch, Schmale, and Vinatzer.
“Are the bacterial strains in this lake plant pathogens? Could freshwater lakes be reservoirs for plant pathogens? These are all questions that we will continue to investigate,” said Schmale.
“It is an excellent opportunity for Claytor Lake State Park to serve as the launching point for this study,” said Theresa Duffey, Natural and Cultural Resource Manager for the Virginia Department of Conservation and Recreation. “The park’s proximity to Virginia Tech makes it an ideal location to facilitate a variety of research projects.”
The project was funded in part by the National Science Foundation’s Dimensions of Biodiversity program. Schmale and Vinatzer are members of Virginia Tech’s Translational Plant Sciences program. Schmale is the director of the Biological Transport interdisciplinary graduate education program at Virginia Tech, formerly known as MultiSTEPS.