[Molecular Microbiology] The studies of ParA and ParB dynamics reveal asymmetry of chromosome segreg
Active segregation of bacterial chromosomes usually involves the action of ParB proteins, which bind in proximity of chromosomal origin (oriC) regions forming nucleoprotein complexes - segrosomes. Newly duplicated segrosomes are moved either uni- or bidirectionally by the action of ATPases – ParA proteins. In Mycobacterium smegmatis the oriC region is located in an off-centred position and newly replicated segrosomes are segregated toward cell poles. The elimination of M. smegmatis ParA and/or ParB leads to chromosome segregation defects. Here, we took advantage of microfluidic time-lapse fluorescent microscopy to address the question of ParA and ParB dynamics in M. smegmatis and M. tuberculosis cells. Our results reveal that ParB complexes are segregated in an asymmetrical manner. The rapid movement of segrosomes is dependent on ParA that is transiently associated with the new pole. Remarkably in M. tuberculosis, the movement of the ParB complex is much slower than in M. smegmatis, but segregation as in M. smegmatis lasts approximately 10% of the cell cycle, which suggests a correlation between segregation dynamics and the growth rate. On the basis of our results, we propose a model for the asymmetric action of segregation machinery that reflects unequal division and growth of mycobacterial cells. This article is protected by copyright. All rights reserved.
Katarzyna Ginda, Isabella Santi, Djenet Bousbaine, Jolanta Zakrzewska-Czerwińska, Dagmara Jakimowicz, John McKinney Accepted manuscript online: 18 May 2017 DOI: 10.1111/mmi.13712