Urea sensitization caused by separation of Helicobacter pylori RNA polymerase beta and beta' subunits.
BACKGROUND
The beta and beta' subunits of RNA polymerase are fused in all Helicobacters, but separate in most other taxa. Prior studies had shown that this fusion is not essential for viability in culture or in vivo, but had not tested it for potentially important quantitative effects on phenotype.


METHODS
The effect of separating rpoB and rpoC sequences on Helicobacter pylori growth was tested in culture and during mouse infection.


RESULTS
Derivatives of strains X47 and SS1 carrying this "rpoBCsplit" allele colonized mice less vigorously than their wild-type parents in competition tests. With X47 rpoBCsplit, this reduced vigor was evident in wild-type mice, whereas with SS1 rpoBCsplit it was seen only in cytokine IL-10- and IL-12beta-deficient mice. In culture, the rpoBCsplit allele sensitized each of four strains tested (X47, SS1, 88-3887, and AM1) to urea, a metabolite that is secreted into the gastric mucosa; urea sensitization was more severe in X47 than in SS1 genetic backgrounds. The rpoBCsplit allele also caused poorer growth on Ham's F12 agar, a nutritionally limiting medium, but had little effect on sensitivity to mild acidity.


CONCLUSIONS
H. pylori's normal RNA polymerase beta-beta' subunit fusion contributes quantitatively to fitness. We propose that urea, although important to H. pylori in vivo, also be considered inhibitory; and that H. pylori's natural beta-beta' subunit fusion helps it cope with urea exposure.
Dailidiene
Daiva
D
Department of Molecular Microbiology, Washington University Medical School, St. Louis, Missouri 63110, USA.
Tan
Shumin
S
Ogura
Keiji
K
Zhang
Maojun
M
Lee
Amy H
AH
Severinov
Konstantin
K
Berg
Douglas E
DE
D000483:Alleles; D000818:Animals; D001426:Bacterial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D003470:Culture Media; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004195:Disease Models, Animal; D016481:Helicobacter Infections / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D014508:Urea / Q000494:pharmacology*
D001426:Bacterial Proteins; D003470:Culture Media; D014508:Urea; C108570:beta' subunit of RNA polymerase; D012321:DNA-Directed RNA Polymerases; C105078:RNA polymerase beta subunit