msbB deletion confers acute sensitivity to CO2 in Salmonella enterica serovar Typhimurium that can be suppressed by a loss-of-function mutation in zwf.
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.
Karsten
Verena
V
Vion Pharmaceuticals, Inc, New Haven, CT 06511, USA. vkarsten@vionpharm.com
Murray
Sean R
SR
Pike
Jeremy
J
Troy
Kimberly
K
Ittensohn
Martina
M
Kondradzhyan
Manvel
M
Low
K Brooks
KB
Bermudes
David
D
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*
D001426:Bacterial Proteins; D003470:Culture Media; D002245:Carbon Dioxide; D005954:Glucosephosphate Dehydrogenase; D000217:Acyltransferases
J Bacteriol. 2007 Jul;189(14):5161-9
17449614
Infect Immun. 1999 Jun;67(6):2815-21
10338486
J Biol Chem. 1997 Apr 18;272(16):10353-60
9099672
J Bacteriol. 1989 Mar;171(3):1751-4
2537826
Infect Immun. 1999 Dec;67(12):6583-90
10569778
J Bacteriol. 2001 Oct;183(19):5554-61
11544217
J Natl Cancer Inst. 1965 Jun;34(6):857-69
4284033
Methods Mol Med. 2004;90:47-60
14657558
Arch Microbiol. 1995 Nov;164(5):324-30
8572885
Infect Immun. 1997 Dec;65(12):5371-5
9393844
FEMS Immunol Med Microbiol. 2008 Mar;52(2):237-46
18177343
Cold Spring Harb Symp Quant Biol. 1981;45 Pt 1:135-40
6271456
Mol Microbiol. 1998 Jul;29(2):571-9
9720873
J Bacteriol. 2000 Jan;182(1):23-9
10613858
Infect Immun. 2000 Jun;68(6):3768-71
10816545
Appl Microbiol Biotechnol. 2004 Mar;64(1):91-8
14661115
J Bacteriol. 1995 Apr;177(7):1742-50
7896696
Clin Cancer Res. 2002 Apr;8(4):1284-91
11948144
J Bacteriol. 1979 Sep;139(3):1093-6
383688
Microbiology (Reading). 2006 Apr;152(Pt 4):1119-1128
16549675
J Bacteriol. 1998 Apr;180(7):1741-9
9537370
Microbiol Mol Biol Rev. 2003 Dec;67(4):593-656
14665678
J Bacteriol. 2004 Dec;186(24):8516-23
15576802
Nat Biotechnol. 1999 Jan;17(1):37-41
9920266
J Clin Oncol. 2002 Jan 1;20(1):142-52
11773163
Infect Immun. 1999 Jan;67(1):436-8
9864251
Infect Immun. 1991 Dec;59(12):4310-7
1937792
Metab Eng. 2004 Apr;6(2):164-74
15113569
Proc Natl Acad Sci U S A. 1990 Aug;87(16):6181-5
1696718
J Bacteriol. 1987 Feb;169(2):856-63
2433267