At some point they must come down to surface where there is water and nutrients to complete the life cycle. Some scientists speculate, though there is no proof, that certain microbes may grow inside of clouds, where there is enough water and some nutrients to support growth. Maybe you will be the one to discover that microbes do indeed grow inside of clouds. Spores Many airborne microbes are in a resting state called spores. One of the functions of spores is to spread organism through the air to distribute the organism geographically.
Spores survive well in the air because they have several important adaptations.
U.V. light is a potent carcinogen for us humans and is deadly to unprotected microbes. Spores that are resistant to U.V. have dark colored pigments that filter out harmful rays - in much the same way that dark glasses protect our eyes from sunburn. Many bacteria form spores as a way to resist harsh conditions such as too little food or water, or excessive heat. Bacterial spores are most prevalent in spring and fall. This bacterium produces a single spore.