title: Genetic determinants of reutericyclin biosynthesis in Lactobacillus reuteri.
abstract: Reutericyclin is a unique antimicrobial tetramic acid produced by some strains of Lactobacillus reuteri. This study aimed to identify the genetic determinants of reutericyclin biosynthesis. Comparisons of the genomes of reutericyclin-producing L. reuteri strains with those of non-reutericyclin-producing strains identified a genomic island of 14 open reading frames (ORFs) including genes coding for a nonribosomal peptide synthetase (NRPS), a polyketide synthase (PKS), homologues of PhlA, PhlB, and PhlC, and putative transport and regulatory proteins. The protein encoded by rtcN is composed of a condensation domain, an adenylation domain likely specific for d-leucine, and a thiolation domain. rtcK codes for a PKS that is composed of a ketosynthase domain, an acyl-carrier protein domain, and a thioesterase domain. The products of rtcA, rtcB, and rtcC are homologous to the diacetylphloroglucinol-biosynthetic proteins PhlABC and may acetylate the tetramic acid moiety produced by RtcN and RtcK, forming reutericyclin. Deletion of rtcN or rtcABC in L. reuteri TMW1.656 abrogated reutericyclin production but did not affect resistance to reutericyclin. Genes coding for transport and regulatory proteins could be deleted only in the reutericyclin-negative L. reuteri strain TMW1.656ΔrtcN, and these deletions eliminated reutericyclin resistance. The genomic analyses suggest that the reutericyclin genomic island was horizontally acquired from an unknown source during a unique event. The combination of PhlABC homologues with both an NRPS and a PKS has also been identified in the lactic acid bacteria Streptococcus mutans and Lactobacillus plantarum, suggesting that the genes in these organisms and those in L. reuteri share an evolutionary origin.
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Xiaoxi B
authors.initials: XB
authors.lastname: Lin
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Lohans
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska, USA.
authors.forename: Rebbeca
authors.initials: R
authors.lastname: Duar
authors.affiliation: State Key Lab of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, People's Republic of China.
authors.forename: Jinshui
authors.initials: J
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada.
authors.forename: John C
authors.initials: JC
authors.lastname: Vederas
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada Department of Biological Sciences, University of Alberta, Edmonton, Alberta, Canada Department of Food Science and Technology, University of Nebraska, Lincoln, Nebraska, USA.
authors.forename: Jens
authors.initials: J
authors.lastname: Walter
authors.affiliation: Department of Agricultural, Food, and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada School of Food and Pharmaceutical Engineering, Hubei University of Technology, Wuhan, People's Republic of China mgaenzle@ualberta.ca.
authors.forename: Michael
authors.initials: M
authors.lastname: Gänzle
mesh_terms: D000900:Anti-Bacterial Agents / Q000096:biosynthesis*; D053898:Biosynthetic Pathways; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D017353:Gene Deletion; D044404:Genomic Islands; D048191:Lactiplantibacillus plantarum / Q000235:genetics; D052200:Limosilactobacillus reuteri / Q000235:genetics* / Q000378:metabolism*; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013295:Streptococcus mutans / Q000235:genetics; D013720:Tenuazonic Acid / Q000031:analogs & derivatives* / Q000096:biosynthesis
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; C416127:reutericyclin; D013720:Tenuazonic Acid