Jack Frost: Do new clothes make him more friendly?

By Gary Raham
Nature Writer and Illustrator

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In the old days, we knew that Jack Frost came out on chilly mornings, waved an icicled finger and created frosty havoc in our gardens.

Any solid surface in contact with air when chilled sufficiently can serve as a site for the formation of the spicules of ice we call frost--beautiful to look at, but capable of lacerating the delicate leaf cells of plants. Sometimes, water will supercool on smooth surfaces and freeze at a temperature below the normal frost point, but on plants something else often happens: Jack starts sharpening up those spicules at temperatures that should be too high for frost.

Sometime in the 1970s, scientists learned that bacteria in the genus Pseudomonas actually cause Jack's schizophrenic behavior. These microbes suck enough energy out of water molecules on the surface of fruits and vegetables to cause frost at higher temperatures than the classic 32 degrees and thus damage citrus and other crops. In 1977, Steven Lindow discovered a mutant strain of Pseudomonas syringae that prevented this frost at higher than expected temperatures--a so-called "ice-minus" strain. Lindow pursued his work at the University of Califorina Berkeley.

About a decade later, a bit of hell broke loose when P. syringae became the first genetically modified (GM) commercial product, called FrostBan.

It turns out that a single gene controls the production of a bacterial coat protein serving as an ice nucleation site for crystallizing water molecules. Take that gene out of P. syringae (or P. fluorescens) and you create a non-nucleating (ice minus) form that can be sprayed on citrus, potatoes and other crops to supplant the ice-plus varieties that normally call such plants home.

In mid-1974, the scary days of early gene manipulation, scientists working in this field took a bold initiative by calling for a temporary moratorium on research and assembling the Asilomar Conference in 1975 on California's Monterey peninsula. Under the scrutiny of news coverage, scientists set up operational guidelines and assessed potential health dangers of the new technology. Research proceeded and ultimately the biotech industry flourished. Scientists breathed a collective sigh of relief, as many of the most alarming concerns of using recombinant DNA seemed unwarranted.

After all, nature does her own genetic recombination all the time--just not with limited, anthropocentric goals in mind.

Nevertheless, Jeremy Rifkin and a coalition of environmentalists called Earth First took notice when UC Berkeley set up the first outdoor trials of FrostBan in Brentwood, Calif., in the late 1980s. Activists crept into the fields the night before the first test and tore half the experimental plants out of the ground, delaying the eventually successful trials for a short time.

Because FrostBan was officially classified as a "pesticide" by EPA, California law required the researchers to wear "moon suits" when conducting the trials. The public heard scientists saying everything was safe, but saw them spraying strawberries looking like characters in "The Andromeda Strain" movie.

It's certainly true that GM technology may yield unexpected and unintended consequences. In 1999, Cornell University published a study that implied that the pollen from corn genetically engineered to contain a toxin designed to repel corn borers might harm monarch butterflies eating nearby milkweed plants. Though the Proceedings of the National Academy of Sciences published six studies in 2001 that GM corn didn't pose a significant risk to monarch populations, the issue still remains contentious--as much for political as scientific reasons.

Healthy skepticism is a good thing. Scientists are born skeptics who use that doubt daily as their most important tool. Consumers need to cultivate informed skepticism, too, as long as it doesn't fester into a blanket rejection of all things new.

FrostBan is still listed as a biocontrol product available in the United States and has the EPA's seal of approval. The EPA factsheet (available online at www.epa.gov/opp00001/biopesticides/ingredients/factsheets/factsheet_006438.htm) says "These naturally occurring bacteria prevent or reduce frost damage to plants by displacing bacteria that induce ice formation...Use of the bacteria listed above as pesticide active ingredients is not expected to cause adverse effects to humans or the environment." EPA took special note of possible effects on bees, as the spring spraying time recommended coincides with bee flower pollination. As of April 2000, four products use one or more P. fluorescens or P. syringae bacterial strains.

Nufarm Americas Inc. now sells Pseudomonas fluorescens A506 under the name BlightBan(r) A506 to commercial orchards, mostly in the Pacific Northwest. It's used for "the reduction of frost and frost damage on cherry, apple, pear, almond, peach, tomato, potato and strawberry." The label comes with comprehensive directions for applying the product with protective clothing, including a dust/mist filtering respirator, and warnings for clean-up procedures and keeping the product out of lakes, ponds and streams. Pesticide applicators don't have to wear moon suits, but obviously the message is "Be careful. This is a living organism with unknown potentials."

Is Jack Frost in the form of Pseudomonas safe now that we've twiddled with his coat proteins and short-circuited his tendency to crystallize water at warmer temperatures than we would like? Probably--as long as we treat him with respect and realize that we can't know everything about how he will behave. We also need well-educated amateur skeptics to keep the professional scientific ones from yelling "Eureka" too quickly--especially now that we have the tools for tinkering with the very fabric of life. Even something as simple as water freezing on a chilly morning gets entangled with a dynamic biosphere always out there interacting and testing the limits of what it means to be alive.