Microbes in the Clouds
One microbial cell is so teeny tiny, but get them together in a huge group and they can change the weather. Yes, change the weather... how is that even possible? Let's get into the facts! Microbes are hardy creatures, and species have evolved to live in a wide range of temperatures, pressures, salinities, oxygen levels, and other conditions. As a result, microbes are found in many extreme environments: think hydrothermal vents at the bottom of the ocean, deserts at high altitudes, and even clouds. As microbes are small and light, it's easy for them to float up on the wind and get into clouds. As the wind helps move microbes around, it may distribute them across different regions of the world. For example, one microbe previously only identified in Japan was found in Oregon. Who knew that microbes were so well-travelled? While they can reach up to about 18 miles above the Earth's surface, many have been found 5 to 9 miles up. When they collected samples from that altitude zone, researchers at Georgia Tech have found one hundred different TYPES of bacteria alone. Fungi are also present. That tells us there are many species and countless individual microbes up there!
There, the microbes must endure a challenging environment of cold temperatures, scarce water, and UV exposure. They are able to survive off of various carbon compounds, such as organic aerosols (substances consisting of particles mixed in air or gas, which can be natural or manmade, like dust or hairspray) and sugars. As some aerosols damage the air quality, it is promising that these microbes eat them and break them down. When they eat the sugars, they use their metabolic by-products to create a protective coating (against threats such as UV exposure) that might also help form clouds.
So how would microbes change the weather? They do so by helping rain or snow form. You may recall that water typically freezes at 32 degrees F, or 0 degrees C. Certain types of bacteria have a protein structure that helps water freeze at warmer-than-usual temperatures. Rain or snow is made of water droplets arranged in a certain pattern. Within the clouds, bacteria serve as scaffolding for the water droplets to attach, form the right pattern and quickly freeze. When they freeze, they will fall to the Earth as rain or snow. A team from Montana State University found evidence of these bacteria in snow samples from North America, Europe, and Antarctica.
How could we apply this idea? If you keep up with the news, you're probably aware of the rising temperatures worldwide. Cloud seeding, where people use drones or aircraft to put substances (such as chemicals or bacteria) in clouds to form more rain or snow, is a way to potentially counteract the effects of global warming. However, the idea should be approached carefully. Too many bacteria could make it difficult for enough water droplets to collect around one particular cell. Similar bacteria also damage plants by covering the plant with frost at above-freezing temperatures, destroying the plant cell wall and consuming its nutrients.
