title: Evolutionary history of the OmpR/IIIA family of signal transduction two component systems in Lactobacillaceae and Leuconostocaceae.
abstract: BACKGROUND
  Two component systems (TCS) are signal transduction pathways which typically consist of a sensor histidine kinase (HK) and a response regulator (RR). In this study, we have analyzed the evolution of TCS of the OmpR/IIIA family in Lactobacillaceae and Leuconostocaceae, two families belonging to the group of lactic acid bacteria (LAB). LAB colonize nutrient-rich environments such as foodstuffs, plant materials and the gastrointestinal tract of animals thus driving the study of this group of both basic and applied interest.
  
  
  RESULTS
  The genomes of 19 strains belonging to 16 different species have been analyzed. The number of TCS encoded by the strains considered in this study varied between 4 in Lactobacillus helveticus and 17 in Lactobacillus casei. The OmpR/IIIA family was the most prevalent in Lactobacillaceae accounting for 71% of the TCS present in this group. The phylogenetic analysis shows that no new TCS of this family has recently evolved in these Lactobacillaceae by either lineage-specific gene expansion or domain shuffling. Furthermore, no clear evidence of non-orthologous replacements of either RR or HK partners has been obtained, thus indicating that coevolution of cognate RR and HKs has been prevalent in Lactobacillaceae.
  
  
  CONCLUSIONS
  The results obtained suggest that vertical inheritance of TCS present in the last common ancestor and lineage-specific gene losses appear as the main evolutionary forces involved in their evolution in Lactobacillaceae, although some HGT events cannot be ruled out. This would agree with the genomic analyses of Lactobacillales which show that gene losses have been a major trend in the evolution of this group.
authors.affiliation: Departamento de Biotecnología de Alimentos, Instituto de Agroquímica y Tecnología de Alimentos, Consejo Superior de Investigaciones Científicas, PO Box 73, 46100 Burjassot, Valencia, Spain. btcman@iata.csic.es
authors.forename: Manuel
authors.initials: M
authors.lastname: Zúñiga
authors.forename: Ciara Luna
authors.initials: CL
authors.lastname: Gómez-Escoín
authors.forename: Fernando
authors.initials: F
authors.lastname: González-Candelas
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D019143:Evolution, Molecular; D000071677:Histidine Kinase; D056584:Leuconostocaceae / Q000145:classification / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; D011494:Protein Kinases; D000071677:Histidine Kinase