Abstract: There is provided a method for controlling a target microorganism characterized in that an extrinsic environmental factor is added to a culture system where said target microorganism and other microbes coexist, said extrinsic environmental factor providing a desirable growth condition for the other microorganisms but an undesirable growth condition for the target microorganism, and said extrinsic environmental factor is typically an organic substance that is assimilable by the above other microorganisms but not by the target microorganism, and includes a sugar, an amino acid, an alkanol amine, an organic acid, and the like. In particular, the target microorganism is N16-1 strain of Burkholderia (FERM BP-5504) and the substance is D-serine.