What is metagenomics and what challenges are associated with assembling genomes from environmental samples?

What is metagenomics and what challenges are associated with assembling genomes from environmental samples?

• A. Metagenomics sequences DNA from mixed communities; challenges include mixed species, uneven abundance, and distinguishing closely related organisms.
• B. Metagenomics sequences genomes of a single species only.
• C. Metagenomics requires all organisms to be cultured in the lab.
• D. Metagenomics yields only functional data, not sequence data.

Answer: (A)

Metagenomics involves sequencing DNA directly from an environmental sample that contains many different organisms, rather than sequencing the genome of a single cultured species. This means you’re trying to reconstruct the genomes of multiple organisms at once from a mixed pool of DNA. The main challenges in assembling genomes from such data come from that mixture. Reads originate from many species, so the assembly process must separate pieces that belong to different organisms. Some microbes are very abundant while others are rare, causing uneven coverage across genomes and making it hard to assemble complete, accurate draft genomes for the low-abundance members. Distinguishing closely related organisms is especially tricky because their genomes are highly similar, which can lead to misassembly or incorrect grouping of contigs into the wrong genome. Together, these issues explain why assembling genomes from environmental metagenomes is difficult, even though metagenomics provides a window into the genetic content of entire communities.

Metagenomics involves sequencing DNA directly from an environmental sample that contains many different organisms, rather than sequencing the genome of a single cultured species. This means you’re trying to reconstruct the genomes of multiple organisms at once from a mixed pool of DNA.

The main challenges in assembling genomes from such data come from that mixture. Reads originate from many species, so the assembly process must separate pieces that belong to different organisms. Some microbes are very abundant while others are rare, causing uneven coverage across genomes and making it hard to assemble complete, accurate draft genomes for the low-abundance members. Distinguishing closely related organisms is especially tricky because their genomes are highly similar, which can lead to misassembly or incorrect grouping of contigs into the wrong genome. Together, these issues explain why assembling genomes from environmental metagenomes is difficult, even though metagenomics provides a window into the genetic content of entire communities.