Abstract: Live attenuated bacteria vaccines are provided. Also provided are methods by which such vaccines can be obtained, including: a method by which a copy of the dam gene from a pathogenic bacteria is cloned into a plasmid capable of replication in the same bacteria species such that it is overexpressed from either a lac promoter, tac promoter, araBAD promoter, trc promoter, trp promoter, T7, SP6, or T5 bacteriophage promoters, a native promoter from that species, or other appropriate promoter. The plasmid containing the dam gene is then transferred into the pathogens to cause increased expression of Dam resulting in the formation of a live attenuated bacterial vaccines. Alternative methods for producing the vaccine are also provided including altering or replacing the chromosomal promoter for the native dam gene so as to alter Dam expression or mutating or replacing the native dam gene so as to alter the expression of Dam in a pathogenic bacteria.