Pseudomons Syringae: The bacteria that can make it rain

Although it is popularly believed that water has a freezing point of 32 degrees Fahrenheit, pure water droplets can be found unfrozen in the atmosphere at temperatures reaching nearly -40 degrees Fahrenheit. These supercooled droplets have the capability of freezing into ice crystals in the presence of ice-nucleating particles. There are several different ice-nucleating particles in the atmosphere. However, researchers believe that bacterial ice nucleation proteins have a profound effect on the supercooled droplets we see in the atmosphere. Bacterial ice nucleation proteins (INPs) allow certain bacteria to produce ice nuclei at comparatively high temperatures (approximately 23 degrees Fahrenheit). These proteins are heavily present in the plant bacteria, Pseudomonas syringae, where they are known as InaZ proteins. Because their INPs are on the outer membrane of the bacterium, P. syringae can interestingly display their effects on water even if the bacteria are alive or dead. With water freezing at higher temperatures, these proteins affect the formation of ice or rain in the atmosphere and can severely damage infected plants and promote frost injury. 

Ice-nucleation proteins (INPs) work by orienting water molecules in certain positions to promote freezing at warmer temperatures. The bacterium can not only arrange water molecules into organized patterns, but it can also transfer thermal energy from the water droplets to itself, leading to a crystal ice lattice structure. Interestingly, P. syringae’s INPs promote the formation of ice nucleation from 6 degrees Fahrenheit to 28 degrees Fahrenheit. 

Pseudomonas syringae can infect a variety of plants including apple, wheat, and pea trees—in fact, they can infect most of the economically important plant species. However, they can also be found in non-agricultural locations, such as the clouds. Current research predicts that there is a positive correlation between the presence of P. syringae and the formation of precipitation in the atmosphere. Bioprecipitation, precipitation caused by bacteria, is an important area to study, as it could influence the water cycle on a larger scale. Scientists have also mimicked the atmospheric conditions caused by P. syringae in a laboratory setting. This research further confirms the presence of P. syringae in rain, snow, and the atmosphere, and enhances the idea that the bacteria disperses through the global water cycle. Current research is set out to understand how to manipulate the bacteria in the atmosphere in order to promote rainfall, an investigation that could serve useful in aiding arid areas.

P. syringae has also been seen in commercial use. Snomax, used to produce artificial snow, is known to be an ice inducer due to its use of dead P. syringae. Snomax extracts the extracellular ice-nucleating proteins from the organism. After they undergo fermentation, the proteins are separated from the fluid and processed through special filters in order to form a slurry, a semiliquid mixture. The slurry is frozen and freeze-dried, producing the artificial snow. Snomax insures that any remaining bacteria at this point are killed through the additional processes. The safe use of this bacterium to create artificial snow has been of great use for ski resorts all around the world. P. syringae also has extensive uses relating to food production, as it has the ability to help preserve frozen foods. By increasing the freezing point of food, businesses lower their expenses and prevent the spoilage of their food. More research needs to be done in order to control this bacteria so that its effects on plants, food, and the environment as a whole remain positive.

Overall, Pseudomonas syringae is an important ice-nucleating bacteria that has unique qualities useful in several different areas of research. It is one of the most prevalent plant bacteria, and can injure a vast majority of plants through frost injury. The bacteria’s capability to affect the food industry, atmosphere, and the production of snow is incredible. Current research emphasizes the power that the bacteria has globally, but more research is undoubtedly needed to manage the bacteria within these settings.