Abstract
ABSTRACT
Structural maintenance of chromosomes (SMC) complexes play conserved roles in chromosome organization, segregation, and repair in all domains of life. In
Bacillus subtilis
, SMC is required for the segregation of newly replicated origins. To investigate whether other proteins function with SMC in this process, we performed a synthetic lethal screen with an
smc
hypomorphic allele (
smc
*) that is mildly defective in chromosome segregation. In addition to recovering previously reported genetic interactions of
smc
with
parB
and
spoIIIE
, our screen identified
minJ
and
divIVA
as essential in the
smc*
background. We show that the synthetic lethality between
smc*
and
∆minJ
or
∆divIVA
arises from defects in segregating the replication terminus. Importantly, deletion of
minD
, which suppresses the cell division defects of
∆minJ
and
∆divIVA
, restored terminus segregation and viability in the
smc*
background. These findings support a model in which proper septum formation promotes chromosome terminus resolution and segregation by enabling SpoIIIE-mediated DNA clearance from the division septum during cytokinesis. These findings highlight the interdependence between chromosome segregation and cell division.
IMPORTANCE
The SMC complex plays a central role in chromosome organization and segregation in
Bacillus subtilis
, but the cellular functions that become important when SMC activity is reduced are not well understood. Using a hypomorphic
smc
allele, we discovered that mutations affecting cell division become essential when chromosome organization and segregation are impaired. Our findings support a model in which efficient septum formation enables proper localization of the SpoIIIE DNA translocase, which in turn resolves and segregates the chromosome terminus region. These results highlight the critical role of cell division in supporting chromosome segregation.