Scientists have found the evidence of rain-making bacteria that are widely distributed in the atmosphere, which could factor heavily into the precipitation cycle, affecting climate, agricultural productivity and even global warming. These bacteria were found by Brent Christner, LSU (Louisiana State University) professor of biological sciences, in partnership with colleagues in Montana and France.
For the research, Christner's team examined precipitation from global locations and demonstrated that the most active ice nuclei - a substrate that enhances the formation of ice - are biological in origin.
This is important because the formation of ice in clouds is required for snow and most rainfall.
Though dust and soot particles can serve as ice nuclei, but biological ice nuclei are capable of catalyzing freezing at much warmer temperatures. If present in clouds, biological ice nuclei may affect the processes that trigger precipitation.
Cloud seeding with silver iodide or dry ice has been done for more than 60 years. Many ski resorts use a commercially available freeze-dried preparation of ice-nucleating bacteria to make snow when the temperature is just a few degrees below freezing.
But, the problem is that most known ice-nucleating bacteria are plant pathogens, which are basically germs that can cause freezing injury in plants, resulting in devastating economic effects on agricultural crop yields.
According to Christner, "As is often the case with bacterial pathogens, other phases of their life cycle are frequently ignored because of the focused interest in their role in plant or animal health."
"Transport through the atmosphere is a very efficient dissemination strategy, so the ability of a pathogen to affect its precipitation from the atmosphere would be advantageous in finding new hosts," he added.
"The role that biological particles play in atmospheric processes has been largely overlooked. However, we have found biological ice nuclei in precipitation samples from Antarctica to Louisiana - they're ubiquitous," said Christner.
"Our results provide an impetus for atmospheric scientists to start thinking about the role these particles play in precipitation," he added.
According to Christner, this work is truly multi-disciplinary, bridging the disciplines of ecology, microbiology, plant pathology and climatology.
"It represents a completely new avenue of research and clearly demonstrates that we are just beginning to understand the intricate interplay between the planet's climate and biosphere," he said.