Ice-minus bacteria
Ice-minus bacteria are a mutant form of a common plant bacterium called Pseudomonas syringae. They lack a surface protein that ice-plus bacteria normally use to help ice form on plant surfaces. Ice-plus bacteria create ice crystals, which can freeze plant buds and cause frost damage. Ice-minus bacteria don’t produce those ice-nucleating crystals, so they are less likely to cause frost.
Scientists used genetic techniques to remove the ice-nucleating gene from P. syringae, creating the ice-minus strain in the lab. The idea was that spraying plants with ice-minus bacteria could reduce frost formation, helping crops stay healthy and produce more yield.
Stephen Lindow and colleagues identified P. syringae as the main cause of ice nucleation in plants in the 1970s and later helped develop the ice-minus strain. A biotech company, Advanced Genetic Sciences (AGS), tested this strain in the field under the product name Frostban.
In 1987, Frostban became the first genetically modified organism released into the environment during field tests on a strawberry field in California. The tests showed promising reductions in frost damage, and similar experiments were done on potato crops as well.
The release sparked strong controversy and legal challenges about environmental and ecological risks. The debate helped shape U.S. regulations for biotechnology, leading to the Coordinated Framework for Regulation of Biotechnology in 1986. Frostban itself was never marketed.
The idea behind this work is simple: if ice-minus bacteria can outcompete ice-plus bacteria on plant surfaces, less frost would form at normal freezing temperatures, reducing crop losses and potentially increasing yields.
This page was last edited on 2 February 2026, at 15:26 (CET).