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Absence of nucleoid occlusion effector Noc impairs formation of orthogonal FtsZ rings during Staphylococcus aureus cell division.
Mol Microbiol. 2011 Jun; 80(5):1366-80
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16 May 2011
William Margolin
F1000 Microbiology
University of Texas at Houston, Medical School,
Houston, TX, USA.
F1000 Microbiology
University of Texas at Houston, Medical School,
Houston, TX, USA.
New Finding
DOI: 10.3410/f.9797956.10497054
This is the first study to show that nucleoid occlusion has an important role in identifying the division planes in Staphylococci.
Staphylococcus aureus, besides being an important human pathogen, is of interest because of the way it divides. The cells form grape-like clusters because they divide in...Continue reading
Staphylococcus aureus, besides being an important human pathogen, is of interest because of the way it divides. The cells form grape-like clusters because they divide in...Continue reading
This is the first study to show that nucleoid occlusion has an important role in identifying the division planes in Staphylococci.
Staphylococcus aureus, besides being an important human pathogen, is of interest because of the way it divides. The cells form grape-like clusters because they divide in three alternating perpendicular planes. In rod-shaped Escherichia coli and Bacillus subtilis cells, the Min and nucleoid occlusion systems form bipolar gradients that together negatively regulate formation of the Z ring, restricting the division plane to the cell midpoint. S. aureus, on the other hand, lacks the Min system, so prior to this paper it was not clear how the nucleoids might influence the plane of Z rings. Here, the authors characterize a homolog of the B. subtilis nucleoid occlusion protein Noc in S. aureus.
They show that in wild-type S. aureus, chromosomal replication origins always segregate prior to assembly of the new Z ring. In S. aureus cells deleted for Noc, Z rings sometimes form on top of unsegregated chromosomes, bisecting them, and form aberrant structures in other nucleoid-free locations. Like nucleoid occlusion proteins of B. subtilis and E. coli, S. aureus Noc mostly localizes poleward, near the respective replication origins, which would generate a bipolar gradient to restrict Z rings to the cell center. Interestingly, Z rings still often formed at the correct division plane in noc- cells, indicating the presence of other spatial regulators of Z ring placement.
It will be fascinating to find these factors, as well as how the chromosomal origins are initially directed to segregate in the correct plane. The authors propose that this occurs in part via geometrical constraints -- segregating origins migrate parallel to the plane of the most recent Z ring, which corresponds to the long axis of a dividing cell. This is reminiscent of how the long axis of dividing spherical E. coli cells forces the Min oscillation pattern to run parallel to the current Z ring, and thus prepare the orthogonal plane for the next division, which, although the mechanism is different from that of S. aureus, has the similar result of allowing these round E. coli to divide in successive alternating planes.
Staphylococcus aureus, besides being an important human pathogen, is of interest because of the way it divides. The cells form grape-like clusters because they divide in three alternating perpendicular planes. In rod-shaped Escherichia coli and Bacillus subtilis cells, the Min and nucleoid occlusion systems form bipolar gradients that together negatively regulate formation of the Z ring, restricting the division plane to the cell midpoint. S. aureus, on the other hand, lacks the Min system, so prior to this paper it was not clear how the nucleoids might influence the plane of Z rings. Here, the authors characterize a homolog of the B. subtilis nucleoid occlusion protein Noc in S. aureus.
They show that in wild-type S. aureus, chromosomal replication origins always segregate prior to assembly of the new Z ring. In S. aureus cells deleted for Noc, Z rings sometimes form on top of unsegregated chromosomes, bisecting them, and form aberrant structures in other nucleoid-free locations. Like nucleoid occlusion proteins of B. subtilis and E. coli, S. aureus Noc mostly localizes poleward, near the respective replication origins, which would generate a bipolar gradient to restrict Z rings to the cell center. Interestingly, Z rings still often formed at the correct division plane in noc- cells, indicating the presence of other spatial regulators of Z ring placement.
It will be fascinating to find these factors, as well as how the chromosomal origins are initially directed to segregate in the correct plane. The authors propose that this occurs in part via geometrical constraints -- segregating origins migrate parallel to the plane of the most recent Z ring, which corresponds to the long axis of a dividing cell. This is reminiscent of how the long axis of dividing spherical E. coli cells forces the Min oscillation pattern to run parallel to the current Z ring, and thus prepare the orthogonal plane for the next division, which, although the mechanism is different from that of S. aureus, has the similar result of allowing these round E. coli to divide in successive alternating planes.
Disclosures
None declared
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Margolin W: F1000Prime Recommendation of [Veiga H et al., Mol Microbiol 2011, 80(5):1366-80]. In F1000Prime, 16 May 2011; DOI: 10.3410/f.9797956.10497054. F1000Prime.com/9797956#eval10497054
F1000Prime Recommendations, Dissents and Comments for [Veiga H et al., Mol Microbiol 2011, 80(5):1366-80]. In F1000Prime, 19 May 2013; F1000Prime.com/9797956
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The Gram-positive pathogen Staphylococcus aureus divides by synthesizing the septum in three orthogonal planes over three consecutive division cycles. This process has to be tightly coordinated with chromosome segregation to avoid bisection of the nucleoid by the septum. Here we show that deletion of the nucleoid occlusion effector Noc in S. aureus results in the formation of Z-rings over the nucleoid, as well as in DNA breaks, indicating that Noc has an important role as an antiguillotine checkpoint that prevents septa from forming over the DNA. Furthermore, Noc deleted cells show multiple Z-rings which are no longer placed in perpendicular planes. We propose that the axis of chromosome segregation has a role in determining the placement of the division septum. This is achieved via the action of Noc which restricts the placement of the division septum to one of an infinite number of potential division planes that exist in S. aureus.
© 2011 Blackwell Publishing Ltd.
DOI: 10.1111/j.1365-2958.2011.07651.x
PMID: 21477126
