Pathoadaptive mutations in Salmonella enterica isolated after serial passage in mice.
How pathogenic bacteria adapt and evolve in the complex and variable environment of the host remains a largely unresolved question. Here we have used whole genome sequencing of Salmonella enterica serovar Typhimurium LT2 populations serially passaged in mice to identify mutations that adapt bacteria to systemic growth in mice. We found unique pathoadaptive mutations in two global regulators, phoQ and stpA, which increase the competitive indexes of the bacteria 3- to 5-fold. Also, all mouse-adapted lineages had changed the orientation of the hin invertable element, resulting in production of a FliC type of flagellum. Competition experiments in mice with locked flagellum mutants showed that strains expressing the FliC type of flagellum had a 5-fold increase in competitive index as compared to those expressing FljB type flagellum. Combination of the flagellum cassette inversion with the stpA mutation increased competitive indexes up to 20-fold. These experiments show that Salmonella can rapidly adapt to a mouse environment by acquiring a few mutations of moderate individual effect that when combined confer substantial increases in growth.
Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
Sanna
S
Koskiniemi
Henry S
HS
Gibbons
Linus
L
Sandegren
Naeem
N
Anwar
Gary
G
Ouellette
Stacey
S
Broomall
Mark
M
Karavis
Paul
P
McGregor
Alvin
A
Liem
Ed
E
Fochler
Lauren
L
McNew
Carolyn Nicole
CN
Rosenzweig
Mikael
M
Rhen
Evan W
EW
Skowronski
Dan I
DI
Andersson
D000222:Adaptation, Physiological / Q000235:genetics*; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D004254:DNA Nucleotidyltransferases / Q000235:genetics* / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D005260:Female; D005407:Flagella / Q000235:genetics / Q000648:ultrastructure; D015964:Gene Expression Regulation, Bacterial; D005809:Genes, Regulator; D016680:Genome, Bacterial; D051379:Mice; D008807:Mice, Inbred BALB C; D018832:Molecular Chaperones / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D012481:Salmonella Infections, Animal / Q000382:microbiology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development / Q000472:pathogenicity; D017422:Sequence Analysis, DNA; D012692:Serial Passage
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D018832:Molecular Chaperones; C079792:PhoQ protein, Bacteria; C548413:StpA protein, Salmonella typhimurium; D004254:DNA Nucleotidyltransferases; C059997:Hin recombinase