Microbial Showers…
uring a cloudburst we often say that it’s Draining “cats and dogs”. In reality, it’s actually raining bacteria; a natural phenomenon that presents no cause for alarm. The sky, once thought of as a sterile void, is actually teeming with bacteria, which are vital for Nuclei are the seeds around watering the plants below. which ice is formed. Snow and most rain begin with the
Jay Hardy, CLS, SM (ASCP) Biological precipitation, or formation of ice in clouds. the "bio-precipitation" cycle Dust and soot can also serve as it is called, starts when as ice nuclei. But biological
bacteria form colonies on the ice nuclei are different from Jay Hardy is the founder and dust and soot nuclei because CEO of Hardy Diagnostics. surface of plants. Winds will He began his career in then sweep the bacteria into only these biological nuclei microbiology as a Medical the atmosphere, and ice can cause freezing at warmer Technologist in Santa crystals form around them. temperatures. Barbara, California. Water molecules clump onto In 1980, he began the crystals, making them manufacturing culture media bigger and bigger. The ice for the local hospitals. crystals turn into rain or snow Today, Hardy Diagnostics is and fall to the ground. When the third largest media manufacturer in the U.S. precipitation occurs, the bacteria have the opportunity To ensure rapid and reliable to make it back down to the turn around time, Hardy ground. If even one bacterium Diagnostics maintains six lands on a plant, it can distribution centers, and produces over 2,700 multiply and form colonies, products used in clinical and thus causing the cycle to industrial microbiology repeat itself over and over. laboratories throughout the
world. David Sands of Montana State University has been studying bio- precipitation for 25 years.
Recent discoveries show that syringae is a mutant, lacking The introduction of an ice- “rain-making bacteria” are the gene responsible for ice- minus strain of P. syringae to more efficient at forming nucleating surface protein the surface of plants causes these nuclei than inert production. competition between the particles, due to their larger strains. Should the ice-minus size and surface area. strain win out, the ice nucleate provided by the wild type P. Minerals can only orient a few syringae would no longer be water molecules but bacterial present, thus lowering the proteins are big and can orient level of frost development on many simultaneously. Ski plant surfaces at normal water resorts exploit this property freezing temperature (0oC) by using attenuated bacteria for the seeding of artificial Everyone knows that water snow. The older method of freezes at 0o C; however few seeding clouds with silver know that ultra pure water Electron micrograph of Pseudomonas iodide has been in use for syringae, which produces a surface (without nuclei forming over 60 years. protein that serves as nuclei around particles) freezes at -40oC. which ice crystals form at warmer temperatures than usual. The ice-forming bacteria Most research to date involves increase the temperature at the ability of Pseudomonas This lack of surface protein which ice crystals form, thus syringae to serve as the nuclei provides a less favorable wreaking havoc for farmers environment for when tender leaves are “…microbes can metabolize and ice formation. destroyed by a coating of ice. grow in clouds, meaning that the Both strains of P. atmosphere may represent an syringae occur In the United States alone, it environment for life” naturally, but has been estimated that frost recombinant accounts for approximately $1 in the promotion of ice DNA technology has allowed billion in crop damage each crystals. “Ice-minus bacteria” for the synthetic removal or year. As P. syringae is a nickname given to a alteration of specific genes, commonly inhabits plant variant of this microorganism. enabling the creation of the surfaces, its ice nucleating This strain of P. syringae ice-minus strain. nature incites frost lacks the ability to produce a development at warmer certain surface protein, usually found on wild-type "ice-plus" P. syringae. The "ice-plus" protein (Ina protein, "Ice nucleation- active" protein) found on the outer bacterial cell wall acts as the nucleating centers for ice crystals. This facilitates ice formation, hence the designation "ice-plus." The ice-minus variant of P. temperatures than 0o C, cloud-borne microbes could freezing the buds of the plant ‘turn on’ their ice nuclear and destroying the crop. proteins in the atmosphere and subsequently be returned Pseudomonas syringae is not to the ground in snow or rain. the only ice nucleator, but is This is a very exciting the most common, and all possibility that further varieties share a common cell research could unearth.” wall protein structure that serves as a scaffold for free- floating water molecules.
The green dots are P. syringae bacteria that are suspended in ice. The bacteria provide a surface for water vapor to join and form ice crystals, which later fall to earth as snow or rain.
The discovery of bio- precipitation has many far reaching implications. For This discovery reminds us example, a reduced amount of once again of the importance bacteria on crops could affect of microbes in our the climate. Because of the environment, even in the sky bio-precipitation cycle, above us. overgrazing in a dry year could actually decrease rainfall, which could then Jay Hardy, CLS, SM (ASCP) make the next year even Santa Maria, CA dryer.
Rain-making bacteria have been found around the globe, even in Antarctica. “Previous work has shown that” said
Brent Christner, a researcher from Louisiana State University. “It is possible that