A method for genetically transforming a strain of the species Bifidobacterium animalis subsp. lactis, comprising the following steps: i) transforming an Escherichia coli strain either: - with a recombinant vector DNA comprising a gene encoding a BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 60% identity with the amino acid sequence SEQ ID NO: 1 and methylates the adenine base at position 4 of the nucleotide sequence RTCAGG and a recombinant vector DNA comprising a gene encoding a BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 55% identity with the amino acid sequence SEQ ID NO: 3 and methylates the cytosine base at position 4 of the nucleotide sequence GGWCC, or - with a recombinant vector DNA comprising both a gene encoding said BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis and a gene encoding said BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis, wherein said recombinant vectors DNA are capable of replicating in said E. coli strain, ii) transforming the E. coli strain of step i) with a recombinant shuttle vector DNA comprising a DNA sequence of interest to introduce in a Bifidobacterium animalis subsp. lactis strain, wherein the said shuttle vector DNA is capable of replicating in the E. coli strain of step i) and in the Bifidobacterium animalis subsp. lactis strain to be targeted for genetic transformation, iii) cultivating the transformed E. coli strain obtained in step ii), iv) extracting the shuttle vector DNA from the transformed E. coli strain, v) transforming, preferably electrotransforming, a Bifidobacterium animalis subsp. lactis strain with the shuttle vector DNA obtained from step iv), vi) recovering the transformed Bifidobacterium animalis subsp. lactis strain of step v). i) transforming an Escherichia coli strain either: - with a recombinant vector DNA comprising a gene encoding a BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 60% identity with the amino acid sequence SEQ ID NO: 1 and methylates the adenine base at position 4 of the nucleotide sequence RTCAGG and a recombinant vector DNA comprising a gene encoding a BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 55% identity with the amino acid sequence SEQ ID NO: 3 and methylates the cytosine base at position 4 of the nucleotide sequence GGWCC, or - with a recombinant vector DNA comprising both a gene encoding said BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis and a gene encoding said BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis, wherein said recombinant vectors DNA are capable of replicating in said E. coli strain, - with a recombinant vector DNA comprising a gene encoding a BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 60% identity with the amino acid sequence SEQ ID NO: 1 and methylates the adenine base at position 4 of the nucleotide sequence RTCAGG and a recombinant vector DNA comprising a gene encoding a BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis that has at least 55% identity with the amino acid sequence SEQ ID NO: 3 and methylates the cytosine base at position 4 of the nucleotide sequence GGWCC, or - with a recombinant vector DNA comprising both a gene encoding said BanLI methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis and a gene encoding said BanLII methyltransferase enzyme from a Bifidobacterium animalis subsp. lactis, ii) transforming the E. coli strain of step i) with a recombinant shuttle vector DNA comprising a DNA sequence of interest to introduce in a Bifidobacterium animalis subsp. lactis strain, wherein the said shuttle vector DNA is capable of replicating in the E. coli strain of step i) and in the Bifidobacterium animalis subsp. lactis strain to be targeted for genetic transformation, iii) cultivating the transformed E. coli strain obtained in step ii), iv) extracting the shuttle vector DNA from the transformed E. coli strain, v) transforming, preferably electrotransforming, a Bifidobacterium animalis subsp. lactis strain with the shuttle vector DNA obtained from step iv), vi) recovering the transformed Bifidobacterium animalis subsp. lactis strain of step v).