Single cell DNA sequencing reveals "dark matter" in microorganisms

Science and Technology Daily News According to the report on the website of nature on July 14 (Beijing time on July 15), astronomers believe that 23% of the total mass of the universe is composed of "dark matter" diffused in it and invisible to the naked eye Now, scientists in the United States have carried out the research on "dark matter" of microorganisms They have sequenced the genomes of various microorganisms with single cell DNA sequencing technology and found that microorganisms are far away It's more diverse than we know, and it's also revealing amazing connections between different species   Single cell sequencing technology enables scientists to decipher the genome of a single cell by increasing its DNA by one billion times, which opens the door for the study of "dark matter" of microorganisms and helps to clarify the relationship between microorganisms and between them and other species The team, led by Tanja Walker of the joint Genomics Institute of the U.S Department of energy, selected 201 microbial and Archaean bacterial cells and read part of their genomes (ranging from 10% to 90%, depending on different cells) None of these microbes have been sequenced or cultured in the laboratory   Studies have shown that many boundaries between different lives are not as solid as previously thought For example, a microbial line synthesized purine bases, the basic components of DNA and RNA, using enzymes previously thought to exist only in archaea The study also shows that there are three sigma factors in archaea cells, which are mainly used to start RNA transcription (the first step of protein biosynthesis), which were previously thought to only appear in bacteria   In addition, the researchers found that a bacterium "records" the three letter sequence of the termination codon UGA In almost all other microorganisms, this sequence of nucleotides sends a signal to the cell to stop translating RNA into proteins; but in this organism, it tells the cell to make aminoglycine Scientists have also found the same "record" activity in another bacterium This suggests that the code of life may be more flexible than scientists think   "We just sequenced a small number of bacteria, and there are so many novel discoveries, which shows that the biological diversity of bacteria is far beyond what we know," Walker said About 16000 cells need to be sequenced to cover half of the world's unexplored microbiota "   "The latest research shows the power of single cell genomics, but it also shows that we need to work harder to bridge the knowledge gap of microbial diversity on earth," said Jeffrey McLean of the Craig Venter Institute (reporter Liu Xia)   Editor in chief circle   The original meaning of "dark matter" of microorganism refers to the microorganism that has never been cultured or sequenced in the laboratory in the past In fact, in many environments, the vast majority of microorganisms can't be cultivated by traditional methods - our traditional microbiology is just the tip of the iceberg in the vast world of microorganisms But scientists have been able to use single cell sequencing to dramatically increase DNA from a single cell by a billion times, and then decipher its genome, thus opening up the way to study the "dark matter" of these microbial communities The results in this paper are based on this method.