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Logo of bmcmicrBioMed Centralsearchsubmit a manuscriptregisterthis articleBMC Microbiology
 
BMC Microbiol. 2012; 12: 32.
Published online Mar 12, 2012. doi:  10.1186/1471-2180-12-32
PMCID: PMC3364868
Alternative sigma factor σH activates competence gene expression in Lactobacillus sakei
Solveig Schmid,1,2,4 Claudia Bevilacqua,3 and Anne-Marie Crutz-Le Coqcorresponding author1
1UMR1319 Micalis, INRA F-78350, Jouy-en-Josas, France
2UMR Micalis, AgroParisTech, INRA F-78350, Jouy-en-Josas, France
3UMR1313 Génétique Animale et Biologie Intégrative, plateforme ICE, INRA F-78350, Jouy-en-Josas, France
4Conceptus SAS, 50 avenue de Saint Cloud, F-78000 Versailles, France
corresponding authorCorresponding author.
Solveig Schmid: solveig.schmid/at/gmail.com; Claudia Bevilacqua: claudia.bevilacqua/at/jouy.inra.fr; Anne-Marie Crutz-Le Coq: Anne-Marie.LeCoq/at/jouy.inra.fr
Received June 8, 2011; Accepted March 12, 2012.
Abstract
Background
Alternative sigma factors trigger various adaptive responses. Lactobacillus sakei, a non-sporulating meat-borne bacterium, carries an alternative sigma factor seemingly orthologous to σH of Bacillus subtilis, best known for its contribution to the initiation of a large starvation response ultimately leading to sporulation. As the role of σH-like factors has been little studied in non-sporulating bacteria, we investigated the function of σH in L. sakei.
Results
Transcription of sigH coding for σH was hardly affected by entry into stationary phase in our laboratory conditions. Twenty-five genes potentially regulated by σH in L. sakei 23 K were revealed by genome-wide transcriptomic profiling of sigH overexpression and/or quantitative PCR analysis. More than half of them are involved in the synthesis of a DNA uptake machinery linked to genetic competence, and in DNA metabolism; however, σH overproduction did not allow detectable genetic transformation. σH was found to be conserved in the L. sakei species.
Conclusion
Our results are indicative of the existence of a genetic competence state activated by σH in L. sakei, and sustain the hypothesis that σH-like factors in non sporulating Firmicutes share this common function with the well-known ComX of naturally transformable streptococci.
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