title: A mimicking-of-DNA-methylation-patterns pipeline for overcoming the restriction barrier of bacteria.
abstract: Genetic transformation of bacteria harboring multiple Restriction-Modification (R-M) systems is often difficult using conventional methods. Here, we describe a mimicking-of-DNA-methylation-patterns (MoDMP) pipeline to address this problem in three difficult-to-transform bacterial strains. Twenty-four putative DNA methyltransferases (MTases) from these difficult-to-transform strains were cloned and expressed in an Escherichia coli strain lacking all of the known R-M systems and orphan MTases. Thirteen of these MTases exhibited DNA modification activity in Southwestern dot blot or Liquid Chromatography-Mass Spectrometry (LC-MS) assays. The active MTase genes were assembled into three operons using the Saccharomyces cerevisiae DNA assembler and were co-expressed in the E. coli strain lacking known R-M systems and orphan MTases. Thereafter, results from the dot blot and restriction enzyme digestion assays indicated that the DNA methylation patterns of the difficult-to-transform strains are mimicked in these E. coli hosts. The transformation of the Gram-positive Bacillus amyloliquefaciens TA208 and B. cereus ATCC 10987 strains with the shuttle plasmids prepared from MoDMP hosts showed increased efficiencies (up to four orders of magnitude) compared to those using the plasmids prepared from the E. coli strain lacking known R-M systems and orphan MTases or its parental strain. Additionally, the gene coding for uracil phosphoribosyltransferase (upp) was directly inactivated using non-replicative plasmids prepared from the MoDMP host in B. amyloliquefaciens TA208. Moreover, the Gram-negative chemoautotrophic Nitrobacter hamburgensis strain X14 was transformed and expressed Green Fluorescent Protein (GFP). Finally, the sequence specificities of active MTases were identified by restriction enzyme digestion, making the MoDMP system potentially useful for other strains. The effectiveness of the MoDMP pipeline in different bacterial groups suggests a universal potential. This pipeline could facilitate the functional genomics of the strains that are difficult to transform.
authors.affiliation: Department of Industrial Microbiology and Biotechnology, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China.
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Zhang
authors.forename: Wenzhao
authors.initials: W
authors.lastname: Wang
authors.forename: Aihua
authors.initials: A
authors.lastname: Deng
authors.forename: Zhaopeng
authors.initials: Z
authors.lastname: Sun
authors.forename: Yun
authors.initials: Y
authors.lastname: Zhang
authors.forename: Yong
authors.initials: Y
authors.lastname: Liang
authors.forename: Yongsheng
authors.initials: Y
authors.lastname: Che
authors.forename: Tingyi
authors.initials: T
authors.lastname: Wen
mesh_terms: D001407:Bacillus / Q000235:genetics; D001419:Bacteria / Q000235:genetics / Q000378:metabolism; D019175:DNA Methylation / Q000235:genetics*; D004262:DNA Restriction Enzymes / Q000235:genetics; D015280:DNA Restriction-Modification Enzymes / Q000235:genetics; D015257:DNA-Cytosine Methylases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli; D009576:Nitrobacter / Q000235:genetics; D012441:Saccharomyces cerevisiae; D014170:Transformation, Genetic
chemical_list: D015280:DNA Restriction-Modification Enzymes; D015257:DNA-Cytosine Methylases; D004262:DNA Restriction Enzymes