Synthetic Lethal Phenotypes Caused by Mutations Affecting Chromosome Partitioning in Bacillus subtilis

Abstract

We investigated the genetic interactions between mutations affecting chromosome structure and partitioning in Bacillus subtilis. Loss-of-function mutations in spoIIIE(encoding a putative DNA translocase) and smc (involved in chromosome structure and partitioning) caused a synthetic lethal phenotype. We constructed a conditional mutation in smc and found that many of the spoIIIE smc double-mutant cells had a chromosome bisected by a division septum. The growth defect of the double mutant was exacerbated by a null mutation in the chromosome partitioning gene spo0J. These results suggest that mutants defective in nucleoid structure are unable to move chromosomes out of the way of the invaginating septum and that SpoIIIE is involved in repositioning these bisected chromosomes during vegetative growth.

Cell division, guillotining of dimer chromosomes and SOS induction in resolution mutants (dif, xerC and xerD) of Escherichia coli

“…These partitioning mutants produced about 5% anucleate cells and, in some cells, septum formation was observed that transected the nucleoid and resulted in products with unequal amounts of DNA. A comparable phenotype has been observed in smc mutants of Bacillus subtilis (Moriya et al, 1998;Britton and Grossman, 1999). In some situations, guillotining can occur at a substantial fraction of the septa.…”

Cell‐specific SpoIIIE assembly and DNA translocation polarity are dictated by chromosome orientation

“…DNA substrate-mediated translocation polarity would provide a mechanism to allow cells to cope with unanticipated consequences of aberrant division or chromosome segregation events. For example, it would allow the precise resolution of chromosomes that pass through the membrane several times, which likely occur in mutants defective in chromosome condensation (Niki et al, 1991;Britton and Grossman, 1999), and which could require the chromosome to be 'snaked' through the membrane. Interestingly, the septa of growing Escherichia coli cells are inherently polarized in a manner nearly identical to the B. subtilis sporulation septum, as both termini often lie in just one of two daughter cells immediately after cell division (Lau et al, 2003).…”

Degradation Process of Mycobacterium leprae Cells in Infected Tissue Examined by the Freeze‐Substitution Method in Electron Microscopy

“…In the last few years the phenomenon of spontaneous cell death by mutated bacteria due to an incomplete separation of chromosome during cell division has been reported (4,11). The DNA sequence of the whole genome of M. leprae has been determined by Cole et al (5) and the possibility that massive gene decay has occurred in the chromosomes of M. leprae was proposed, based on comparisons to the genome of M. tuberculosis.…”