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The 19 superbugs that rule Earth's hidden depths
THIS WEEK
Catherine Brahic
MEET the super-invaders of deep Earth. The same 19 microbes are found throughout Earth’s crust from Canada to Indonesia, most likely living at the very limit of life. Nobody knows how these cosmopolitan bugs went global. On the surface, different places are home to different organisms, even if conditions are similar: Antarctica has penguins, but the Arctic has polar bears. A species only spreads widely if it can travel freely. “It is easy to understand how birds and fish might be similar oceans apart,” says Matt Schrenk of Michigan State University in East Lansing. “But it challenges the imagination to think of nearly identical microbes 16,000 kilometres apart in the cracks of hard rock.” Schrenk is part of a global team probing depths up to 2 kilometres beneath the surface. They use mineshafts, wells and drilling rigs, scattered around the world (see map, right). Samples are sent to the Marine Biological Laboratory in Woods Hole, Massachusetts, where Sharon
Dyslexia’s roots traced to bad chat in the brain THE neural basis of dyslexia may finally have been nailed. It seems that different areas of the brain’s language network don’t communicate properly. The discovery may lead to ways of helping people with dyslexia improve reading and writing skills. One theory proposes that people with dyslexia have subtle hearing problems, particularly involving timing of speech, which in turn leads 12 | NewScientist | 14 December 2013
Deep Earth community Teams drilling deep into Earth’s crust at different sites keep finding the same bits of microbial DNA everywhere they look. Nobody knows how the microbes got there
SOURCE: CENSUS OF DEEP LIFE
to the brain’s neural representation of phonemes – the basic units of speech sounds – developing poorly. The trouble with this idea, says Sophie Scott at University College London, is that people with dyslexia have no problem understanding speech. To investigate, Scott and her colleagues scanned the brains of 23 adults with dyslexia and 22 without. In all the participants, patterns of nerve activity in the auditory cortex, which processes incoming sound, were equally reliable in their response to different speech sounds. This suggests that
the brain represents sounds equally well, whether or not a person has dyslexia. Another possibility is that other parts of the brain’s language network may have trouble accessing those sound representations. To test this, the team explored connections between 13 brain regions involved in language processing. They looked at how similar activity was across these regions and the structure of the
“The study points to using brain stimulation to target faulty connections to improve reading”
Robert Harding Picture Library Ltd / Alamy
Deep Earth zombie bugs went global
how they get from a Canadian mine to methane pockets under the Indonesian sea floor. Alternatively, subsurface bacteria around the planet may be forced to evolve in similar ways by the limited resources available. So Grim analyses the DNA they hold. far, Grim has focused on a single gene that is often used to identify “There seems to be a core types of bacteria. The microbes group of microbes that appears might carry similar versions of again and again in all these that gene but not be closely related. environments,” says Rick Colwell Schrenk offers a more radical of Oregon State University in idea. Many of the organisms were Corvallis, who presented Grim’s found in serpentine minerals, results at a meeting of the which form under conditions American Geophysical Union in similar to the ones that may have San Francisco this week. “Some prevailed where life first started might be very rare, just a fraction more than 4 billion years ago. of a per cent of the total life present – however, they are there.” He says the microbes could have evolved in similar primordial The team is flummoxed when habitats, and been carried around it comes to explaining the find. Maybe the buried microbes move the globe by plate tectonics. “These results imply a around, but it is tough to imagine
–Microbes down below–
commonality of colonisation of the [planet’s] subsurface,” agrees Barbara Sherwood-Lollar of the University of Toronto in Canada. “Determining how and when that happened is the next critical step.” Colwell is less comfortable saying the organisms spread from a single location. But given how stable conditions are in the depths, he says the microbes may have been there for aeons. “I’m willing to think about the subsurface biosphere as being the once and future refuge for microbial life,” he says. “When the sun goes through its cycle and Earth is fried, that will be the last place where life will wink out.” We don’t yet know how the microbes survive. There is little to eat in the deep, so they might be at the limit of life. “Thinking of them as the living dead may not be far off,” says Colwell. n
actual nerves that connect them. In people with dyslexia, both types of test revealed faulty connections, and therefore bad communication, between the brain region that contains the auditory cortex and the area involved in language processing and speech production. The poorer the connectivity between these regions, the worse participants performed on reading and other phonological tasks (Science, doi.org/qcw). The team suggest that noninvasive brain stimulation techniques might be able to restore the faulty connections. Simon Makin n
Catherine Brahic
MEET the super-invaders of deep Earth. The same 19 microbes are found throughout Earth’s crust from Canada to Indonesia, most likely living at the very limit of life. Nobody knows how these cosmopolitan bugs went global. On the surface, different places are home to different organisms, even if conditions are similar: Antarctica has penguins, but the Arctic has polar bears. A species only spreads widely if it can travel freely. “It is easy to understand how birds and fish might be similar oceans apart,” says Matt Schrenk of Michigan State University in East Lansing. “But it challenges the imagination to think of nearly identical microbes 16,000 kilometres apart in the cracks of hard rock.” Schrenk is part of a global team probing depths up to 2 kilometres beneath the surface. They use mineshafts, wells and drilling rigs, scattered around the world (see map, right). Samples are sent to the Marine Biological Laboratory in Woods Hole, Massachusetts, where Sharon
Dyslexia’s roots traced to bad chat in the brain THE neural basis of dyslexia may finally have been nailed. It seems that different areas of the brain’s language network don’t communicate properly. The discovery may lead to ways of helping people with dyslexia improve reading and writing skills. One theory proposes that people with dyslexia have subtle hearing problems, particularly involving timing of speech, which in turn leads 12 | NewScientist | 14 December 2013
Deep Earth community Teams drilling deep into Earth’s crust at different sites keep finding the same bits of microbial DNA everywhere they look. Nobody knows how the microbes got there
SOURCE: CENSUS OF DEEP LIFE
to the brain’s neural representation of phonemes – the basic units of speech sounds – developing poorly. The trouble with this idea, says Sophie Scott at University College London, is that people with dyslexia have no problem understanding speech. To investigate, Scott and her colleagues scanned the brains of 23 adults with dyslexia and 22 without. In all the participants, patterns of nerve activity in the auditory cortex, which processes incoming sound, were equally reliable in their response to different speech sounds. This suggests that
the brain represents sounds equally well, whether or not a person has dyslexia. Another possibility is that other parts of the brain’s language network may have trouble accessing those sound representations. To test this, the team explored connections between 13 brain regions involved in language processing. They looked at how similar activity was across these regions and the structure of the
“The study points to using brain stimulation to target faulty connections to improve reading”
Robert Harding Picture Library Ltd / Alamy
Deep Earth zombie bugs went global
how they get from a Canadian mine to methane pockets under the Indonesian sea floor. Alternatively, subsurface bacteria around the planet may be forced to evolve in similar ways by the limited resources available. So Grim analyses the DNA they hold. far, Grim has focused on a single gene that is often used to identify “There seems to be a core types of bacteria. The microbes group of microbes that appears might carry similar versions of again and again in all these that gene but not be closely related. environments,” says Rick Colwell Schrenk offers a more radical of Oregon State University in idea. Many of the organisms were Corvallis, who presented Grim’s found in serpentine minerals, results at a meeting of the which form under conditions American Geophysical Union in similar to the ones that may have San Francisco this week. “Some prevailed where life first started might be very rare, just a fraction more than 4 billion years ago. of a per cent of the total life present – however, they are there.” He says the microbes could have evolved in similar primordial The team is flummoxed when habitats, and been carried around it comes to explaining the find. Maybe the buried microbes move the globe by plate tectonics. “These results imply a around, but it is tough to imagine
–Microbes down below–
commonality of colonisation of the [planet’s] subsurface,” agrees Barbara Sherwood-Lollar of the University of Toronto in Canada. “Determining how and when that happened is the next critical step.” Colwell is less comfortable saying the organisms spread from a single location. But given how stable conditions are in the depths, he says the microbes may have been there for aeons. “I’m willing to think about the subsurface biosphere as being the once and future refuge for microbial life,” he says. “When the sun goes through its cycle and Earth is fried, that will be the last place where life will wink out.” We don’t yet know how the microbes survive. There is little to eat in the deep, so they might be at the limit of life. “Thinking of them as the living dead may not be far off,” says Colwell. n
actual nerves that connect them. In people with dyslexia, both types of test revealed faulty connections, and therefore bad communication, between the brain region that contains the auditory cortex and the area involved in language processing and speech production. The poorer the connectivity between these regions, the worse participants performed on reading and other phonological tasks (Science, doi.org/qcw). The team suggest that noninvasive brain stimulation techniques might be able to restore the faulty connections. Simon Makin n