A global atlas of soil bacteria

19 January 2018
Posted by Lewis Thomson.

Soil samples from all over the world have been studied to uncover the bacteria they contain. The vast majority of the microbes revealed by the technique don't even have names...

When we think about bacteria, we tend to conjure mental images of nasty pathogens that give us disease. But bacteria are incredibly diverse in a number of ways – including where they live and how they interact with their environments. Thousands of different bacterial strains live inside the human body, many of them essential to helping us to digest our food properly.

Huge communities of bacteria are also found in the ground beneath our feet, most of them in the soil where tens of thousands of different types live around plant roots. And just like the bacteria that live in us, some are harmful pathogens but many are essential for the plants’ survival. Without these bacteria, it's likely that there would be no plants, no land animals, and no humans.

Yet, despite their huge importance and abundance, we know almost nothing about soil bacteria. But now, publishing their work in Science, scientists at the University of Colorado have taken steps to change this by comparing the bacterial populations living in soil samples from all over the world.

Led by Noah Fierer, the Colorado team took soil samples from 237 locations across six continents. They used genetic sequencing techniques to read the DNA and identify the different types of bacteria in each sample.

“Despite the enormous diversity of soil bacteria, we find that there’s a relatively small subset – about 500 types – that are dominant,” explains Fierer. “In other words, this 2% of soil bacteria types account for about half of the bacteria cells in most samples worldwide.”

Interestingly, most of the dominant types uncovered by the team had never been sequenced before. The genetic sequencing identified them as being distinct types, but the team couldn’t identify what they were because they'd not been documented previously.

“Most of them, we know nothing about. They don’t have a name, we don’t know what they’re doing in soil, and we haven’t grown them in the laboratory. It really highlights how little we still know about those organisms living in soil,” says Fierer.

The team hope that, armed with the knowledge of where different types of soil bacteria live, they can now begin to understand how environmental conditions affect bacterial communities and how this, in turn, affects the growth of plants, including important crops.

“The next step is to figure out what these dominant types are doing, and how they may be influencing soil health. Many are likely beneficial, and that’s an exciting area of future research – figuring out how we can manage soil microbial communities to better grow crops," explains Fierer...

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