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Identifcation of new hosts-dependants factors in Bacillus cereus Molecular and functional characterization of IlsA, a surface protein essential for iron acquisition during infection

Nadine Daou
Abstract : Bacillus cereus is frequently associated with food-borne gastroenteritis and can be responsible for severe opportunistic infections. Adaptation factors involved in the pathogenicity of B. cereus are still unknown. The ability to acquire ion during infection, is an important adaptation factor that allow bacteria to overcome the lack of iron imposed by the host. Our work has led to the identification of new factors involved in the adaptation of B. cereus in the host and to the characterization of a novel protein IlsA (Iron regulated leucine-rich surface protein) highly expressed in the host. These factors were identified using the IVET (In Vivo Expression Technology) system, which was adapted to the strain B. cereus ATCC 14579 and screened after infection in the insect larvae Galleria mellonella. This system detects transient activated promoters. The protein structure analysis of IlsA shows four distinct domains: an N-terminal signal peptide for export, a NEAT domain thought to be involved in iron transport, a leucine-rich repeat domain that may interact with host cells, and an SLH domain presumably binding the protein to the bacterial surface. The presence of a fur box in the promoter region of ilsA suggests an iron dependent regulation. Indeed, the transcriptional analysis showed that ilsA is expressed under iron restricted conditions in vitro and in vivo. In addition, we have shown that IlsA is located on the bacterial surface and that is required for iron acquisition from the host proteins: hemoglobin, heme and ferritin, by direct binding to them. Furthermore, the protein sequence of the NEAT domain of IlsA, suggests that it could be responsible for the interaction with the heme. Disruption of ilsA reduced the survival and the virulence of B. cereus in the insect and in a mice macrophage cell line. Our results indicate that IlsA is an adaptation factor that play an essential role in iron acquisition during infection and thus contribute to the pathogenesis of B. cereus in both invertebrates and vertebrates
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https://pastel.archives-ouvertes.fr/pastel-00004926
Contributor : Ecole Agroparistech <>
Submitted on : Monday, March 23, 2009 - 8:00:00 AM
Last modification on : Monday, March 23, 2009 - 8:00:00 AM
Long-term archiving on: : Thursday, September 30, 2010 - 8:53:10 PM

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Nadine Daou. Identifcation of new hosts-dependants factors in Bacillus cereus Molecular and functional characterization of IlsA, a surface protein essential for iron acquisition during infection. Life Sciences [q-bio]. AgroParisTech, 2008. English. ⟨NNT : 2008AGPT0068⟩. ⟨pastel-00004926⟩

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