title: Genome diversification within a clonal population of pandemic Vibrio parahaemolyticus seems to depend on the life circumstances of each individual bacteria.
abstract: BACKGROUND
  New strains of Vibrio parahaemolyticus that cause diarrhea in humans by seafood ingestion periodically emerge through continuous evolution in the ocean. Influx and expansion in the Southern Chilean ocean of a highly clonal V. parahaemolyticus (serotype O3:K6) population from South East Asia caused one of the largest seafood-related diarrhea outbreaks in the world. Here, genomics analyses of isolates from this rapidly expanding clonal population offered an opportunity to observe the molecular evolutionary changes often obscured in more diverse populations.
  
  
  RESULTS
  Whole genome sequence comparison of eight independent isolates of this population from mussels or clinical cases (from different years) was performed. Differences of 1366 to 217,729 bp genome length and 13 to 164 bp single nucleotide variants (SNVs) were found. Most genomic differences corresponded to the presence of regions unique to only one or two isolates, and were probably acquired by horizontal gene transfer (HGT). Some DNA gain was chromosomal but most was in plasmids. One isolate had a large region (8,644 bp) missing, which was probably caused by excision of a prophage. Genome innovation by the presence of unique DNA, attributable to HGT from related bacteria, varied greatly among the isolates, with values of 1,366 (ten times the number of highest number of SNVs) to 217,729 (a thousand times more than the number of highest number of SNVs).
  
  
  CONCLUSIONS
  The evolutionary forces (SNVs, HGT) acting on each isolate of the same population were found to differ to an extent that probably depended on the ecological scenario and life circumstances of each bacterium.
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. david.loyola@omics-solutions.cl.
authors.forename: David E
authors.initials: DE
authors.lastname: Loyola
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. cristell.navarro@omics-solutions.cl.
authors.forename: Cristell
authors.initials: C
authors.lastname: Navarro
authors.affiliation: Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, El Líbano 5524, Santiago, Chile. pau.uribe@gmail.com.
authors.forename: Paulina
authors.initials: P
authors.lastname: Uribe
authors.affiliation: Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, El Líbano 5524, Santiago, Chile. kata.garcia@gmail.com.
authors.forename: Katherine
authors.initials: K
authors.lastname: García
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. cmellahernandez@gmail.com.
authors.forename: Claudia
authors.initials: C
authors.lastname: Mella
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. didiaz09@alumnos.utalca.cl.
authors.forename: Diego
authors.initials: D
authors.lastname: Díaz
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. nvaldesp@alumnos.utalca.cl.
authors.forename: Natalia
authors.initials: N
authors.lastname: Valdes
authors.affiliation: Depatment of Biology and Biochemistry, University of Bath, Claverton Down, Bath, North East Somerset, BA2 7AY, UK. j.l.martinez-urtaza@bath.ac.uk.
authors.forename: Jaime
authors.initials: J
authors.lastname: Martínez-Urtaza
authors.affiliation: Centro Nacional de Genómica y Bioinformática, Av B. O'Higgins 340, Santiago, Chile. romilio.espejo@gmail.com.|Instituto de Nutrición y Tecnología de los Alimentos, Universidad de Chile, El Líbano 5524, Santiago, Chile. romilio.espejo@gmail.com.
authors.forename: Romilio T
authors.initials: RT
authors.lastname: Espejo
mesh_terms: D000818:Animals; D049872:Bivalvia / Q000382:microbiology; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology; D022761:Gene Transfer, Horizontal; D014644:Genetic Variation; D016680:Genome, Bacterial; D006801:Humans; D058873:Pandemics; D010957:Plasmids / Q000235:genetics / Q000378:metabolism; D020641:Polymorphism, Single Nucleotide; D014735:Vibrio Infections / Q000453:epidemiology / Q000382:microbiology; D014736:Vibrio parahaemolyticus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification