THE earth beneath our feet may be teeming with 100 times as many species of bacteria as we thought. One gram of dirt can harbour a million microbial species, according to a re-analysis of DNA data.
Measuring the bacterial biodiversity of soil is difficult because only a few species can be cultured for testing in the lab. Biologists therefore have to estimate biodiversity using a technique called DNA re-association. This involves unzipping the two strands of every bacterial genome in a sample, mixing them up and timing how long they take to rejoin. If all the DNA strands were the…
