(JP10323192-A)      A plasmid is characterised by having base sequence (I; given in the specification).    Also claimed are:    (1) a plasmid with about 1.8 kb base pairs as given in the specification;    (2) a similar plasmid with base sequence (II; given in the specification), particularly containing 1.9 kb base pairs;    (3) a plasmid containing at least a part of the above base sequences and a selective marker gene;    (4) a plasmid with 7.6 kb base pairs as given in the specification;    (5) a transformant prepared by introducing a plasmid into 1 host;    (6) a bioluminescence detection method for detecting ammonium ion in an aqueous solution by contacting the substrate with a transformant obtained by introducing a plasmid, that has a gene containing protein(s) encoding for bioluminescence, into an ammonia oxidising bacterium;    (7) a method for producing nitrification-inhibiting material-resistant ammonia oxidising bacteria using a transformant obtained by introducing a plasmid, that has a gene encoding metabolism and decomposition enzyme for nitrification-inhibiting materials, into ammonia oxidising bacteria, and    (8) a method for enhancing ammonia oxidation of ammonia oxidising bacteria using a transformant obtained by introducing a plasmid that has a gene encoding an enzyme for ammonia oxidation.    USE -   The plasmid can be used as a transformation vector for gene manipulation in ammonia oxidising bacteria such as Nitrosomonas europaea after introduction into hosts to prepare transformants for treating underground water, household aqueous waste and industrial effluent by the activated sludge or bio-membrane method.    ADVANTAGE -   Said plasmid, pAYS, is characterised by having base sequences and a selective marker gene, which can be used as transformation vector for gene manipulation.    (EP1016725-A1)      A plasmid is characterised by having base sequence (I; given in the specification).    Also claimed are:    (1) a plasmid with about 1.8 kb base pairs as given in the specification;    (2) a similar plasmid with base sequence (II; given in the specification), particularly containing 1.9 kb base pairs;    (3) a plasmid containing at least a part of the above base sequences and a selective marker gene;    (4) a plasmid with 7.6 kb base pairs as given in the specification;    (5) a transformant prepared by introducing a plasmid into 1 host;    (6) a bioluminescence detection method for detecting ammonium ion in an aqueous solution by contacting the substrate with a transformant obtained by introducing a plasmid, that has a gene containing protein(s) encoding for bioluminescence, into an ammonia oxidising bacterium;    (7) a method for producing nitrification-inhibiting material-resistant ammonia oxidising bacteria using a transformant obtained by introducing a plasmid, that has a gene encoding metabolism and decomposition enzyme for nitrification-inhibiting materials, into ammonia oxidising bacteria, and    (8) a method for enhancing ammonia oxidation of ammonia oxidising bacteria using a transformant obtained by introducing a plasmid that has a gene encoding an enzyme for ammonia oxidation.    USE -   The plasmid can be used as a transformation vector for gene manipulation in ammonia oxidising bacteria such as Nitrosomonas europaea after introduction into hosts to prepare transformants for treating underground water, household aqueous waste and industrial effluent by the activated sludge or bio-membrane method.    ADVANTAGE -   Said plasmid, pAYS, is characterised by having base sequences and a selective marker gene, which can be used as transformation vector for gene manipulation.