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Title: Sporulation initiation in Clostridium difficile

Speaker: Mónica Serrano

Affiliation: Microbial Development, ITQB NOVA

Abstract:

Bacteria that reside in the gastrointestinal tract of healthy humans are essential for our health, sustenance and well-being. About 50 to 60% of those bacteria have the ability to produce resilient spores, important for the life cycle in the gut and for host-to-host transmission. Recently a genomic signature of sporulation within the human intestinal microbiome was described. We report on the identification of a new gene, termed csiA, part of the genomic signature for sporulation in the gut, which is involved in the control of sporulation initiation in Clostridium difficile. We show that csiA is expressed during growth. The in-frame deletion of csiA results in increased sporulation. The key regulatory protein for entry into sporulation is Spo0A, which is activated by phosphorylation. We show that deletion of csiA increases the expression of spo0A per cell, and also the expression of the Spo0A-dependent spoIIG operon, coding for the first mother cell specific RNA polymerase sigma factor, sE. In contrast, deletion of csiA did not increase the expression of the Spo0A-dependent spoIIA operon, coding for the first forespore-specific sigma factor, sF. Increased expression of spoIIG results in increased production and proteolytic activation of pro-sE, suggesting that the levels of active sE are a limiting factor for sporulation. Together, our results indicate that csiA gene is a specific negative regulator of sporulation. The presence of csiA in a genomic signature for sporulation in the gut suggests that this gene has an important role in controlling sporulation initiation in vivo.