Quorum sensing controls the production of the siderophore malleobactin in Burkholderia thailandensis E264

Cayuela Sánchez, German (2019). Quorum sensing controls the production of the siderophore malleobactin in Burkholderia thailandensis E264 Mémoire. Québec, Université du Québec, Institut national de la recherche scientifique, Maîtrise en microbiologie appliquée, 56 p.

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Résumé

Siderophores are chelating molecules with a very high affinity for Fe3+, an essential element for the survival of most living organisms. These molecules are produced and secreted by bacteria under iron-limiting conditions. Malleobactin and pyochelin are siderophores produced by the bacterium Burkholderia thailandensis, a closely related bacterium to B. pseudomallei and B. mallei that is not pathogenic to humans. Several species of Gram-negative bacteria communicate by synthesizing, secreting, and responding to small diffusible signal molecules, N-acyl homoserine lactones (AHLs), through a mechanism called quorum sensing (QS). The AHLs-mediated cell-to-cell signaling allows these bacteria to coordinate gene expression and regulate different functions such as biofilm formation and virulence factors. The signal molecules are produced by an AHL synthase gene luxI at low concentration and are diffusing around the cells. Transcription of QS-regulated target genes appears by LuxR homologue proteins only when high AHL concentration is present, which required a threshold bacterial cell density. Like B. pseudomallei has the bpsIR quorum sensing system, in B. thailandensis there are three complete quorum sensing systems (each including a synthase for a corresponding signal molecule), BtaIR1, BtaIR2 and BtaIR3; and two orphan regulators, BtaR4 and BtaR5. Our hypothesis is that QS regulates the production of the siderophore malleobactin in B. thailandensis E264. First we measured siderophore production with a colorimetric method using CAS dye (chrome azurol S) in different mutants of pyochelin and maleobactin synthesis and determined that malleobactin acts as the main siderophore under iron depleted conditions. Then, the different quorum sensing mutants available in our laboratory (btaI1, btaI2, btaI3, btaI1,2,3, btaR1, btaR2, btaR3, btaR4 and btaR5) were investigated. This allowed us to identify positive and negative regulation of siderophore production. Finally, we quantified the expression of the mbaA gene (the first gene for the operon of malleobactin synthesis) in these mutants using the qRT-PCR method. This study provides insights into the role of intercellular communication in the production of the main siderophore produced by B. thailandensis.

Type de document:	Thèse Mémoire
Directeur de mémoire/thèse:	Déziel, Éric
Mots-clés libres:	-
Centre:	Centre INRS-Institut Armand Frappier
Date de dépôt:	18 juill. 2023 14:01
Dernière modification:	18 juill. 2023 14:01
URI:	https://espace.inrs.ca/id/eprint/13316

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