title: Methyltransferases acquired by lactococcal 936-type phage provide protection against restriction endonuclease activity.
abstract: BACKGROUND
  So-called 936-type phages are among the most frequently isolated phages in dairy facilities utilising Lactococcus lactis starter cultures. Despite extensive efforts to control phage proliferation and decades of research, these phages continue to negatively impact cheese production in terms of the final product quality and consequently, monetary return.
  
  
  RESULTS
  Whole genome sequencing and in silico analysis of three 936-type phage genomes identified several putative (orphan) methyltransferase (MTase)-encoding genes located within the packaging and replication regions of the genome. Utilising SMRT sequencing, methylome analysis was performed on all three phages, allowing the identification of adenine modifications consistent with N-6 methyladenine sequence methylation, which in some cases could be attributed to these phage-encoded MTases. Heterologous gene expression revealed that M.Phi145I/M.Phi93I and M.Phi93DAM, encoded by genes located within the packaging module, provide protection against the restriction enzymes HphI and DpnII, respectively, representing the first functional MTases identified in members of 936-type phages.
  
  
  CONCLUSIONS
  SMRT sequencing technology enabled the identification of the target motifs of MTases encoded by the genomes of three lytic 936-type phages and these MTases represent the first functional MTases identified in this species of phage. The presence of these MTase-encoding genes on 936-type phage genomes is assumed to represent an adaptive response to circumvent host encoded restriction-modification systems thereby increasing the fitness of the phages in a dynamic dairy environment.
authors.forename: James
authors.initials: J
authors.lastname: Murphy
authors.forename: Jochen
authors.initials: J
authors.lastname: Klumpp
authors.forename: Jennifer
authors.initials: J
authors.lastname: Mahony
authors.forename: Mary
authors.initials: M
authors.lastname: O'Connell-Motherway
authors.forename: Arjen
authors.initials: A
authors.lastname: Nauta
authors.affiliation: School of Microbiology, University College Cork, Cork, Ireland. d.vansinderen@ucc.ie.
authors.forename: Douwe
authors.initials: D
authors.lastname: van Sinderen
mesh_terms: D000595:Amino Acid Sequence; D001435:Bacteriophages / Q000201:enzymology* / Q000235:genetics / Q000502:physiology*; D002611:Cheese / Q000382:microbiology; D019175:DNA Methylation; D004262:DNA Restriction Enzymes / Q000378:metabolism*; D016679:Genome, Viral / Q000235:genetics; D023281:Genomics; D013294:Lactococcus lactis / Q000821:virology*; D008780:Methyltransferases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data
chemical_list: D008780:Methyltransferases; D004262:DNA Restriction Enzymes