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    • Figs.
      (left) Random metagenomic library (E. coli hosts), right arrow: capability test
      (upper-right) Pigment production: production of various pigments such as blue, red, yellow, purple, and fluorescent can be confirmed visually. some of them are luminescent clones that glow at night (they have acquired a luminescent gene)
      (middle-right) Siderophore production: We have added a pigment to the medium that turns yellow when siderophores (substances necessary for the acquisition of iron, an essential nutrient. siderophores' structure varies among bacteria)  are present
      (lower-right) Production of antibacterial substances: when a metagenomic clone produces an antimicrobial substance, the bacteria around the clone die and black circles appear.

       The obtained fragments of metagenomic DNA are randomly incorporated into a culturable host such as E. coli. Each of the colonies in the lower left photo contains a different metagenomic DNA fragment.

      Each colony is called a metagenomic clone, and the aggregate (the entire plate in this example) is called a metagenomic library.

      If the metagenome contains a gene that is required to produce some substance (such as a pigment), the clone will produce that substance ( in the case of a pigment, the colony will be colored).

    • {Column}
      In many cases, multiple genes are required to make a single compound.
      Fortunately, in bacteria, the necessary genes are often found in a continuous and coherent set (called a gene cluster).
       Therefore, it is possible to incorporate all the necessary genes together into a single clone.
      In the case of the biosynthetic gene cluster of antimicrobial substances, self-resistance genes are also included.

    • Advantages and disadvantages of method 1)

      Advantages

      Genes that have never been sequenced before can be obtained.
      No need for DNA sequencing costs.

      Disadvantages

      Metagenomic genes do not always work in E. coli.
      Difficult (but not impossible) when multiple genes are required.
      It takes time and effort.