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The impact of EngA, EngB, Era and Obg GTPases on the cell cycle of Streptococcus pneumoniae

Takkal, Adil
(2025)

Files

TAKKAL_Adil_42462000_2024-2025pdf.pdf
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Details

Supervisors
Dewachter, Liselot
Faculty
Faculté de pharmacie et des sciences biomédicales
Degree label
Master [120] en sciences biomédicales, à finalité approfondie
Abstract
Streptococcus pneumoniae accounted for 15% of all deaths among children under five in 2017. It also causes life-threatening infections in adults over 65 or individuals with comorbidities. To fight S. pneumoniae infections, effective antibiotics are needed. However, S. pneumoniae has already developed resistance to many of the currently used antibiotics, making the search for new therapeutic targets increasingly urgent. A potential approach is to study the mechanisms underlying bacterial growth and division. Therefore, this thesis focuses on four universally conserved bacterial GTPases: EngA, EngB, Era, and Obg. These GTPases are essential in S. pneumoniae and have been linked to cell cycle processes in other bacteria. However, due to pleiotropic effects and the lack of integrated overexpression and depletion studies, their precise roles remain unclear. To address this, we generated S. pneumoniae overexpression and depletion strains for each GTPase using inducible promoters. Since Ptet depletion strains were unable to grow, we switched to Plac strains. Subsequently, growth was assessed through spot tests and OD growth curves assays. Overexpression strains grew similarly to the wild-type strain, while depletion strains exhibited growth defects, albeit not always as strong as expected for essential genes. Afterwards, the impact of these GTPases on S. pneumoniae chromosome segregation and cell division has been analyzed through microscopy. Although present only in a minority of cells, a chromosome segregation defect has been identified in both overexpression and depleted strains. Interestingly, this defect was mostly present in elongated cells, potentially implying a role of the GTPases in coordinating chromosome segregation event with cell division processes. The experiments conducted during this thesis aim to elucidate the impact of these four GTPases in the S. pneumoniae cell cycle and may contribute to potentially identifying new targets for antibiotic development.