title: msbB deletion confers acute sensitivity to CO2 in Salmonella enterica serovar Typhimurium that can be suppressed by a loss-of-function mutation in zwf.
abstract: BACKGROUND
  Pathogens tolerate stress conditions that include low pH, oxidative stress, high salt and high temperature in order to survive inside and outside their hosts. Lipopolysaccharide (LPS), which forms the outer-leaflet of the outer membrane in Gram-negative bacteria, acts as a permeability barrier. The lipid A moiety of LPS anchors it to the outer membrane bilayer. The MsbB enzyme myristoylates the lipid A precursor and loss of this enzyme, in Salmonella, is correlated with reduced virulence and severe growth defects that can both be compensated with extragenic suppressor mutations.
  
  
  RESULTS
  We report here that msbB (or msbB somA) Salmonella are highly sensitive to physiological CO2 (5%), resulting in a 3-log reduction in plating efficiency. Under these conditions, msbB Salmonella form long filaments, bulge and lyse. These bacteria are also sensitive to acidic pH and high osmolarity. Although CO2 acidifies LB broth media, buffering LB to pH 7.5 did not restore growth of msbB mutants in CO2, indicating that the CO2-induced growth defects are not due to the effect of CO2 on the pH of the media. A transposon insertion in the glucose metabolism gene zwf compensates for the CO2 sensitivity of msbB Salmonella. The msbB zwf mutants grow on agar, or in broth, in the presence of 5% CO2. In addition, msbB zwf strains show improved growth in low pH or high osmolarity media compared to the single msbB mutant.
  
  
  CONCLUSIONS
  These results demonstrate that msbB confers acute sensitivity to CO2, acidic pH, and high osmolarity. Disruption of zwf in msbB mutants restores growth in 5% CO2 and results in improved growth in acidic media or in media with high osmolarity. These results add to a growing list of phenotypes caused by msbB and mutations that suppress specific growth defects.
authors.affiliation: Vion Pharmaceuticals, Inc, New Haven, CT 06511, USA. vkarsten@vionpharm.com
authors.forename: Verena
authors.initials: V
authors.lastname: Karsten
authors.forename: Sean R
authors.initials: SR
authors.lastname: Murray
authors.forename: Jeremy
authors.initials: J
authors.lastname: Pike
authors.forename: Kimberly
authors.initials: K
authors.lastname: Troy
authors.forename: Martina
authors.initials: M
authors.lastname: Ittensohn
authors.forename: Manvel
authors.initials: M
authors.lastname: Kondradzhyan
authors.forename: K Brooks
authors.initials: KB
authors.lastname: Low
authors.forename: David
authors.initials: D
authors.lastname: Bermudes
mesh_terms: D000217:Acyltransferases / Q000235:genetics*; D001426:Bacterial Proteins / Q000235:genetics; D002245:Carbon Dioxide / Q000494:pharmacology*; D003470:Culture Media; D015964:Gene Expression Regulation, Bacterial; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics; D006863:Hydrogen-Ion Concentration; D016254:Mutagenesis, Insertional; D009154:Mutation; D012486:Salmonella typhimurium / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D002245:Carbon Dioxide; D005954:Glucosephosphate Dehydrogenase; D000217:Acyltransferases
references.citation: J Bacteriol. 2007 Jul;189(14):5161-9
references.pmid: 17449614
references.citation: Infect Immun. 1999 Jun;67(6):2815-21
references.pmid: 10338486
references.citation: J Biol Chem. 1997 Apr 18;272(16):10353-60
references.pmid: 9099672
references.citation: J Bacteriol. 1989 Mar;171(3):1751-4
references.pmid: 2537826
references.citation: Infect Immun. 1999 Dec;67(12):6583-90
references.pmid: 10569778
references.citation: J Bacteriol. 2001 Oct;183(19):5554-61
references.pmid: 11544217
references.citation: J Natl Cancer Inst. 1965 Jun;34(6):857-69
references.pmid: 4284033
references.citation: Methods Mol Med. 2004;90:47-60
references.pmid: 14657558
references.citation: Arch Microbiol. 1995 Nov;164(5):324-30
references.pmid: 8572885
references.citation: Infect Immun. 1997 Dec;65(12):5371-5
references.pmid: 9393844
references.citation: FEMS Immunol Med Microbiol. 2008 Mar;52(2):237-46
references.pmid: 18177343
references.citation: Cold Spring Harb Symp Quant Biol. 1981;45 Pt 1:135-40
references.pmid: 6271456
references.citation: Mol Microbiol. 1998 Jul;29(2):571-9
references.pmid: 9720873
references.citation: J Bacteriol. 2000 Jan;182(1):23-9
references.pmid: 10613858
references.citation: Infect Immun. 2000 Jun;68(6):3768-71
references.pmid: 10816545
references.citation: Appl Microbiol Biotechnol. 2004 Mar;64(1):91-8
references.pmid: 14661115
references.citation: J Bacteriol. 1995 Apr;177(7):1742-50
references.pmid: 7896696
references.citation: Clin Cancer Res. 2002 Apr;8(4):1284-91
references.pmid: 11948144
references.citation: J Bacteriol. 1979 Sep;139(3):1093-6
references.pmid: 383688
references.citation: Microbiology (Reading). 2006 Apr;152(Pt 4):1119-1128
references.pmid: 16549675
references.citation: J Bacteriol. 1998 Apr;180(7):1741-9
references.pmid: 9537370
references.citation: Microbiol Mol Biol Rev. 2003 Dec;67(4):593-656
references.pmid: 14665678
references.citation: J Bacteriol. 2004 Dec;186(24):8516-23
references.pmid: 15576802
references.citation: Nat Biotechnol. 1999 Jan;17(1):37-41
references.pmid: 9920266
references.citation: J Clin Oncol. 2002 Jan 1;20(1):142-52
references.pmid: 11773163
references.citation: Infect Immun. 1999 Jan;67(1):436-8
references.pmid: 9864251
references.citation: Infect Immun. 1991 Dec;59(12):4310-7
references.pmid: 1937792
references.citation: Metab Eng. 2004 Apr;6(2):164-74
references.pmid: 15113569
references.citation: Proc Natl Acad Sci U S A. 1990 Aug;87(16):6181-5
references.pmid: 1696718
references.citation: J Bacteriol. 1987 Feb;169(2):856-63
references.pmid: 2433267