[SCAN] Unveiling new mechanisms of chromosome segregation in Staphylococcus aureus

Title: Unveiling new mechanisms of chromosome segregation in Staphylococcus aureus

Speaker: Simon Schaeper

From: Bacterial Cell Biology Lab, ITQB NOVA

Abstract: For bacteria to proliferate, they must duplicate their genetic material and pass on one copy of their chromosome to each daughter cell. Bacteria lack a mitotic spindle and, given their small size, face unique challenges in maintaining genome integrity while condensing and segregating their chromosomes in a coordinated manner.
In the Bacterial Cell Biology lab, we use the clinically relevant pathogen Staphylococcus aureus as a model, aiming to better understand the basic principles of bacterial growth and division to possibly build unifying models. Chromosome segregation in near-spherical cells of S. aureus is incompletely understood, even though it is thought play an important role in division site selection in this organism. By visualizing individual chromosomal loci in live cells, we recently showed that the staphylococcal chromosome adopts a longitudinal cellular arrangement, and that chromosome replication and cell division cycles are not synchronized, as cells are usually born with a partially replicated chromosome.

More recently, our lab identified RicO (Regulator and Insulator of Chromosomal Origins) as a new factor of S. aureus chromosome biology. Cells lacking RicO fail to position replication origins at the cell poles and have weakened genomic interactions in the origin-proximal region. Our findings support a model in which RicO acts as a bridge between replication origins and the cell membrane, thereby ensuring formation of two nucleoid-containing sister cells in S. aureus.

SCANs are weekly seminars that happen every Wednesday at noon by in-house researchers and invited speakers at ITQB NOVA.