Sky-high bacteria could affect climate, scientists say – Los Angeles Times


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Sky-high bacteria could affect climate, scientists say – Los Angeles Times

  1. 1. Sky-high bacteria could affect climate, scientists say – LosAngeles TimesA team of storm-chasing scientists sampling rarefied air has found a world of bacteria and fungifloating about 30,000 feet above Earth. The findings, detailed Monday in the Proceedings of theNational Academy of Sciences, suggest that microbes have the potential to affect the weather.Scientists have long studied airborne bacteria, but they typically do so from the ground, oftentrekking to mountain peaks to examine microbes in fresh snow. Beyond that, they don’t knowmuch about the number and diversity of floating microbes, said study coauthor AthanasiosNenes, an atmospheric scientist at Georgia Tech.To get a glimpse of this hovering world, Nenes and his colleagues hitched several rides on aNASA aircraft as onboard instruments sampled the air before, during and after hurricanes Earland Karl in 2010. The plane flew into the upper troposphere, about 6 miles above the surface. Also World’s megacities may influence global weather Obama signals new focus on climate change 1/4
  2. 2. Sandy and drought propel U.S. insurance lossesDuring nine flights — most over the Caribbean and the midwest Atlantic — the researchers ranthe outside air over a series of filters, each time capturing material from an average of 212 cubicfeet of ambient air. They sampled a variety of environments, from the cloudy masses thatpreceded Hurricane Earl to the cloud-free air after Hurricane Karl passed.The researchers focused on a ribosomal RNA gene called SSU rRNA, which can reliablyidentify bacterial species. They calculated that there were about 144 bacterial cells per cubicfoot of air.The bacteria accounted for 20% of the particles in their size range — stuff that scientists hadassumed was just sea salt and dust.“We were surprised,” Nenes said.The filters picked up fungi too, though in concentrations that were at most only 10% as high asfor the bacteria.The microbial populations were very different before and after a storm, Nenes said; that makessense, given that hurricanes have the potential to kick a fresh batch of bugs into the air.Among other types, the scientists found Escherichia and Streptococcus bacteria in theirsamples — microbes typically associated with human and animal feces that could have been 2/4
  3. 3. thrown into the air as the storms swept through populated areas.The researchers identified 17 types of bacteria that were found in all the samples, leading theteam to suspect that those organisms constituted a core microbiome for the lower atmosphere.These bacteria must have developed traits that allowed them to bear freezing temperatures,feed on the scarce carbon compounds in cloud dust and survive in an environment bombardedby ultraviolet radiation.Other studies have revealed the presence of plant-based microbes that are thought to inducefreezing in order to damage leaves and then infect them.Microbes with this freezing ability could conceivably collect water vapor and seed clouds,causing them to release rain. It could very well represent a way of transporting microbes acrosscontinents, Nenes said.That possibility also has implications for the ways in which illnesses spread, he added.“Once you get to that altitude, if you can survive, you can basically circulate the Earth veryquickly,” Nenes said. “You can start out in Europe and end up in Asia.”The finding could be exciting for astrobiologists, who wonder about the extreme environments inwhich bacteria can live on Earth — and whether they could do so on other planets as well.“It definitely lends to the idea that life is pretty resilient and you can adapt to almost anyenvironment if you have a bare minimum of sustenance,” Nenes said.The paper provides a fascinating preliminary census of the airborne microbes, said DavidSands, a bacteriologist at Montana State University who was not involved in the study. 3/4
  4. 4. But such research has a long way to go before proving that microbes in the atmosphere are doing anything other than waiting for their slow fall back to Earth, he added. “If they go up, they want to get back down,” Sands said. Source Article from,0, ory Sky-high bacteria could affect climate, scientists say – Los Angeles Times 4/4Powered by TCPDF (