Author for correspondence: Kurt Nordström. Tel: +46 18 471 45 26. Fax: +46 18 53 03 96. e-mail: Kurt.Nordstroem@icm.uu.se
a†Thoms Åkerlund nd Björn Gullbrnd contributed eqully to this work.
b ‡Present address: Department of Molecular and Cell Biology, Division of Biochemistry and Molecular Biology, University of California, Berkeley, CA 94720, USA.
The Min system of Escherichia coli directs cell division to the mid-cell by a mechanism that involves the dynamic localization of all of its three constituent proteins, MinC, MinD and MinE. Both the Min system and the nucleoid regulate cell division negatively and strains of E. coli lacking a functional Min system can divide at nucleoid-free cell poles in addition to the nucleoid-free region between newly segregated nucleoids. Interestingly, E. coli strains with a defective Min system have disturbed nucleoid segregation and the cause for this disturbance is not known. It is reported here that growth conditions promoting a higher frequency of polar divisions also lead to a more pronounced disturbance in nucleoid segregation. In strains with an intact Min system, expression of MinE, but not of MinD, from an inducible promoter was followed by impaired nucleoid segregation. These results suggest that the disturbed nucleoid segregation in min mutants is not caused by polar divisions per se, nor by impaired resolution of chromosome dimers in min mutants, leaving open the possibility that the Min system has a direct effect on nucleoid segregation. It is also shown how the disturbed nucleoid segregation can explain in part the unexpected finding that the clear majority of cells in min mutant populations contain 2n (n=0, 1, 2…) origins of replication.
BoyleD. S,
GrantD,
DraperG. C.,
DonachieW. D.
2000; All major regions of FtsK are required for resolution of chromosome dimers. J Bacteriol 182:4124–4127
de BoerP. A,
CrossleyR. E.,
RothfieldL. I.
1989; A division inhibitor and a topological specificity factor coded for by the minicell locus determine proper placement of the division septum in E. coli
. Cell 56:641–649
de BoerP. A,
CrossleyR. E,
HandA. R.,
RothfieldL. I.
1991; The MinD protein is a membrane ATPase required for the correct placement of the Escherichia coli division site. EMBO J 10:4371–4380
de BoerP. A,
CrossleyR. E.,
RothfieldL. I.
1992; Roles of MinC and MinD in the site-specific septation block mediated by the MinCDE system of Escherichia coli
. J Bacteriol 174:63–70
GrinstedJ,
SaundersJ. R,
IngramL. C,
SykesR. B.,
RichmondM. H.
1972; Properties of an R factor which originated in Pseudomonas aeruginosa 1822. J Bacteriol 110:529–537
GullbrandB.,
NordströmK.
2000; FtsZ ring formation without subsequent cell division after replication runout in Escherichia coli
. Mol Microbiol 36:1349–1359
HuZ.,
LutkenhausJ.
1999; Topological regulation of cell division in Escherichia coli involves rapid pole to pole oscillation of the division inhibitor MinC under the control of MinD and MinE. Mol Microbiol 34:82–90
HuZ.,
LutkenhausJ.
2001; Topological regulation of cell division in E. coli spatiotemporal oscillation of MinD requires stimulation of its ATPase by MinE and phospholipid. Mol Cell 7:1337–1343
HuZ,
MukherjeeA,
PichoffS.,
LutkenhausJ.
1999; The MinC component of the division site selection system in Escherichia coli interacts with FtsZ to prevent polymerization. Proc Natl Acad Sci USA 96:14819–14824
MulderE,
El’BouhaliM,
PasE.,
WoldringhC. L.
1990; The Escherichia coli minB mutation resembles gyrB in defective nucleoid segregation and decreased negative supercoiling of plasmids. Mol Gen Genet 221:87–93
PéralsK,
CornetF,
MerletY,
DelonI.,
LouarnJ.-M.
2000; Functional polarization of the Escherichia coli chromosome terminus: the dif site acts in chromosome dimer resolution only when located between long stretches of opposite polarity. Mol Microbiol 36:33–43
RaskinD. M.,
de BoerP. A.
1997; The MinE ring: an FtsZ-independent cell structure required for selection of the correct division site in E. coli
. Cell 91:685–694
RaskinD. M.,
de BoerP. A.
1999b; Rapid pole-to-pole oscillation of a protein required for directing division to the middle of Escherichia coli
. Proc Natl Acad Sci USA 96:4971–4976
SteinerW. W.,
KuempelP. L.
1998; Cell division is required for resolution of dimer chromosomes at the dif locus of Escherichia coli
. Mol Microbiol 27:257–268
TeatherR. M,
CollinsJ. F.,
DonachieW. D.
1974; Quantal behavior of a diffusible factor which initiates septum formation at potential division sites in Escherichia coli
. J Bacteriol 118:407–413
WoldringhC. L,
MulderE,
ValkenburgJ. A,
WientjesF. B,
ZaritskyA.,
NanningaN.
1990; Role of the nucleoid in the toporegulation of division. Res Microbiol 141:39–49
YuX. C.,
MargolinW.
1999; FtsZ ring clusters in min and partition mutants: role of both the Min system and the nucleoid in regulating FtsZ ring localization. Mol Microbiol 32:315–326
YuX. C,
TranA. H,
SunQ.,
MargolinW.
1998; Localization of cell division protein FtsK to the Escherichia coli septum and identification of a potential N-terminal targeting domain. J Bacteriol 180:1296–1304