title: A new piece of the Shigella Pathogenicity puzzle: spermidine accumulation by silencing of the speG gene [corrected].
abstract: The genome of Shigella, a gram negative bacterium which is the causative agent of bacillary dysentery, shares strong homologies with that of its commensal ancestor, Escherichia coli. The acquisition, by lateral gene transfer, of a large plasmid carrying virulence determinants has been a crucial event in the evolution towards the pathogenic lifestyle and has been paralleled by the occurrence of mutations affecting genes, which negatively interfere with the expression of virulence factors. In this context, we have analysed to what extent the presence of the plasmid-encoded virF gene, the major activator of the Shigella regulon for invasive phenotype, has modified the transcriptional profile of E. coli. Combining results from transcriptome assays and comparative genome analyses we show that in E. coli VirF, besides being able to up-regulate several chromosomal genes, which potentially influence bacterial fitness within the host, also activates genes which have been lost by Shigella. We have focused our attention on the speG gene, which encodes spermidine acetyltransferase, an enzyme catalysing the conversion of spermidine into the physiologically inert acetylspermidine, since recent evidence stresses the involvement of polyamines in microbial pathogenesis. Through identification of diverse mutations, which prevent expression of a functional SpeG protein, we show that the speG gene has been silenced by convergent evolution and that its inactivation causes the marked increase of intracellular spermidine in all Shigella spp. This enhances the survival of Shigella under oxidative stress and allows it to better face the adverse conditions it encounters inside macrophage. This is supported by the outcome of infection assays performed in mouse peritoneal macrophages and of a competitive-infection assay on J774 macrophage cell culture. Our observations fully support the pathoadaptive nature of speG inactivation in Shigella and reveal that the accumulation of spermidine is a key determinant in the pathogenicity strategy adopted by this microrganism.
authors.affiliation: Department of Biology and Biotechnology "C.Darwin", Institut Pasteur-Fondazione Cenci Bolognetti, University of "Sapienza" Rome, Rome, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Barbagallo
authors.forename: Maria Letizia
authors.initials: ML
authors.lastname: Di Martino
authors.forename: Lucia
authors.initials: L
authors.lastname: Marcocci
authors.forename: Paola
authors.initials: P
authors.lastname: Pietrangeli
authors.forename: Elena
authors.initials: E
authors.lastname: De Carolis
authors.forename: Mariassunta
authors.initials: M
authors.lastname: Casalino
authors.forename: Bianca
authors.initials: B
authors.lastname: Colonna
authors.forename: Gianni
authors.initials: G
authors.lastname: Prosseda
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D002470:Cell Survival; D002478:Cells, Cultured; D004405:Dysentery, Bacillary / Q000235:genetics* / Q000382:microbiology; D004926:Escherichia coli / Q000235:genetics / Q000472:pathogenicity; D020868:Gene Silencing; D017737:Macrophages, Peritoneal / Q000378:metabolism; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D018384:Oxidative Stress; D010957:Plasmids / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D018085:Regulon; D012763:Shigella flexneri / Q000235:genetics / Q000472:pathogenicity*; D013095:Spermidine / Q000378:metabolism*; D059467:Transcriptome; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D012333:RNA, Messenger; D037521:Virulence Factors; D013095:Spermidine
references.citation: Res Microbiol. 2007 Jul-Aug;158(6):487-93
references.pmid: 17656072
references.citation: J Clin Microbiol. 1994 May;32(5):1179-83
references.pmid: 8051242
references.citation: FEMS Microbiol Lett. 2007 Feb;267(1):1-8
references.pmid: 17233672
references.citation: Biochem J. 1999 Dec 15;344 Pt 3:633-42
references.pmid: 10585849
references.citation: Mol Microbiol. 2004 Jan;51(2):437-46
references.pmid: 14756784
references.citation: Cell Microbiol. 2006 Feb;8(2):177-84
references.pmid: 16441429
references.citation: Infect Immun. 1986 Nov;54(2):395-402
references.pmid: 3021627
references.citation: Infect Immun. 2004 Aug;72(8):4424-31
references.pmid: 15271899
references.citation: J Bacteriol. 2006 Apr;188(7):2355-63
references.pmid: 16547021
references.citation: Infect Immun. 2005 Jan;73(1):88-102
references.pmid: 15618144
references.citation: Mol Microbiol. 2008 Apr;68(1):4-16
references.pmid: 18405343
references.citation: Bull World Health Organ. 1999;77(8):651-66
references.pmid: 10516787
references.citation: Wei Sheng Wu Xue Bao. 2008 Jul;48(7):905-10
references.pmid: 18837368
references.citation: Trends Microbiol. 1999 May;7(5):191-5
references.pmid: 10354593
references.citation: Cell Immunol. 2003 Dec;226(2):86-94
references.pmid: 14962496
references.citation: J Biochem. 1991 Apr;109(4):627-31
references.pmid: 1869516
references.citation: Biochem Biophys Res Commun. 2003 Feb 21;301(4):915-22
references.pmid: 12589799
references.citation: Proc Natl Acad Sci U S A. 2003 Mar 4;100(5):2261-5
references.pmid: 12591940
references.citation: J Bacteriol. 1997 Jul;179(14):4486-92
references.pmid: 9226257
references.citation: Cell Microbiol. 1999 Sep;1(2):143-55
references.pmid: 11207548
references.citation: Science. 1997 Sep 5;277(5331):1453-62
references.pmid: 9278503
references.citation: J Biol Chem. 1995 Aug 11;270(32):18831-5
references.pmid: 7642535
references.citation: Microbes Infect. 2002 Sep;4(11):1125-32
references.pmid: 12361912
references.citation: Can J Physiol Pharmacol. 1987 Oct;65(10):2024-35
references.pmid: 3322538
references.citation: Curr Top Microbiol Immunol. 2009;337:231-55
references.pmid: 19812985
references.citation: Infect Immun. 1982 Mar;35(3):852-60
references.pmid: 6279518
references.citation: Curr Opin Microbiol. 2001 Oct;4(5):550-7
references.pmid: 11587932
references.citation: Am J Physiol. 1990 Apr;258(4 Pt 1):G576-84
references.pmid: 2333971
references.citation: Mol Microbiol. 2000 Nov;38(4):760-71
references.pmid: 11115111
references.citation: Mol Microbiol. 2004 Jan;51(2):523-37
references.pmid: 14756791
references.citation: Microbiology (Reading). 2011 Feb;157(Pt 2):504-515
references.pmid: 20966092
references.citation: PLoS One. 2007 Dec 12;2(12):e1291
references.pmid: 18074016
references.citation: Agents Actions. 1992 May;36(1-2):17-21
references.pmid: 1384285
references.citation: Gene. 1987;53(1):85-96
references.pmid: 3596251
references.citation: Mol Microbiol. 2003 Jan;47(2):519-27
references.pmid: 12519201
references.citation: Proc Natl Acad Sci U S A. 1983 Feb;80(3):653-7
references.pmid: 6187001
references.citation: Antimicrob Agents Chemother. 1979 Dec;16(6):743-9
references.pmid: 533256
references.citation: Res Microbiol. 2002 Sep;153(7):461-8
references.pmid: 12405354
references.citation: Proc Natl Acad Sci U S A. 2000 Jun 6;97(12):6640-5
references.pmid: 10829079
references.citation: Immunopharmacol Immunotoxicol. 2004 Feb;26(1):93-101
references.pmid: 15106734
references.citation: Infect Immun. 2001 Dec;69(12):7471-80
references.pmid: 11705922
references.citation: Curr Opin Microbiol. 1999 Apr;2(2):188-94
references.pmid: 10322176
references.citation: Adv Exp Med Biol. 2007;603:106-15
references.pmid: 17966408
references.citation: J Bacteriol. 1988 Jul;170(7):3131-5
references.pmid: 3290196
references.citation: Mol Microbiol. 2001 Oct;42(2):439-52
references.pmid: 11703666
references.citation: J Bacteriol. 1989 Aug;171(8):4457-65
references.pmid: 2666401
references.citation: J Bacteriol. 1992 Apr;174(8):2659-69
references.pmid: 1556085
references.citation: Microbiol Rev. 1985 Mar;49(1):81-99
references.pmid: 3157043
references.citation: Methods. 2001 Dec;25(4):402-8
references.pmid: 11846609
references.citation: J Bacteriol. 2008 Feb;190(3):872-8
references.pmid: 18039771
references.citation: J Biol Chem. 2007 Apr 13;282(15):11009-20
references.pmid: 17314093
references.citation: Biochemistry (Mosc). 2003 Aug;68(8):850-6
references.pmid: 12948384
references.citation: Microbiology (Reading). 2009 Aug;155(Pt 8):2498-2508
references.pmid: 19460819
references.citation: FEMS Microbiol Lett. 2009 Oct;299(2):166-74
references.pmid: 19694812
references.citation: Ann N Y Acad Sci. 2006 Aug;1072:307-12
references.pmid: 17057210
references.citation: Nature. 2000 May 18;405(6784):299-304
references.pmid: 10830951
references.citation: Infect Immun. 1992 Nov;60(11):4740-6
references.pmid: 1398984
references.citation: Infect Immun. 1999 May;67(5):2160-5
references.pmid: 10225869
references.citation: J Infect Dis. 2001 Sep 15;184(6):743-53
references.pmid: 11517436