Abstract: A method of producing coryneform bacteria having an improved amino acid or nucleic acid-productivity comprises the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium so that it is close to a consensus sequence or introducing a change in the promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on the chromosome of a coryneform bacterium by gene recombination so that it is close to a consensus sequence, obtaining mutants of the coryneform amino acid- or nucleic acid-producing microorganism, culturing the mutants and select a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method allows one of skill in the art to construct a mutant capable of enriching or controlling the expression of an intended gene without using a plasmid and to promote production of amino acids in a high yield, by the recombination or mutation.

Abstract: A method of producing coryneform bacteria having an improved amino acid- or nucleic acid-productivity comprises the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium to make it close to a consensus sequence or introducing a change in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium by gene recombination to make it close to a consensus sequence, to obtain mutants of the coryneform amino acid d- or nucleic acid-producing microorganism, culturing the mutants and select a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method can construct a mutant capable of suitably enriching or controling the expression of an intended gene without using a plasmid and also capable of producing amino acids in a high yield, by the recombination or mutation.

Abstract: A method of producing coryneform bacteria having improved amino acid or nucleic acid productivity comprising the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium to make it close to a consensus sequence, or introducing a change in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium by gene recombination to make it close to a consensus sequence, to obtain mutants of the coryneform amino acid- or nucleic acid-producing microorganism, culturing the mutants and selecting a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method allows the construction of a mutant capable of enriching or controlling the expression of an intended gene without using a plasmid and to promote production of amino acids in a high yield by recombination or mutation.

Abstract: A method of producing coryneform bacteria having an improved amino acid- or nucleic acid-productivity comprises the steps of introducing a mutation in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium to make it close to a consensus sequence or introducing a change in a promoter sequence of amino acid- or nucleic acid-biosynthesizing genes on a chromosome of a coryneform bacterium by gene recombination to make it close to a consensus sequence, to obtain mutants of the coryneform amino acid- or nucleic acid-producing microorganism, culturing the mutants and select a mutant capable of producing the intended amino acid or nucleic acid in a large amount. This method can construct a mutant capable of suitably enriching or controling the expression of an intended gene without using a plasmid and also capable of producing amino acids in a high yield, by the recombination or mutation.

Abstract: A coryneform bacterium in which a DNA fragment is incorporated into its chromosome is prepared by (a) obtaining a recombinant plasmid through ligation of a DNA fragment having a sequence homologous to a gene present on a chromosome of a coryneform bacterium to a plasmid that has a wild-type replication control region segment of a particular nucleotide sequence including a mutation and is autonomously replicable in a coryneform bacterium cell at a culture temperature lower than 31° C. but not autonomously replicable in the cell at a temperature of 31° C. or higher, (b) introducing the recombinant plasmid into the coryneform bacterium cell, (c) culturing the bacterium at a temperature of 31° C. or higher, (d) causing homologous recombination between the DNA fragment and the gene present on the chromosome of the coryneform bacterium and having a sequence homologous to the DNA fragment, and (e) selecting a coryneform bacterium in which the DNA fragment is incorporated into its chromosome.