Hello #MicroTwJc Fans!

Next Tuesday’s #microtwjc paper (which has just been published this month) is one for all bacteriologists (and virologists that like bacteria!) as it has implications for all bacteria due to the conservation of the bacteria cell cycle.

Title“FtsZ Placement in Nucleoid-Free Bacteria”

Authors: Manuel Pazos, Mercedes Casanova, Pilar Palacios, William Margolin, Paolo Natale, and Miguel Vicente

Abstract: We describe the placement of the cytoplasmic FtsZ protein, an essential component of the division septum, in nucleoid-free Escherichia coli maxicells. The absence of the nucleoid is accompanied in maxicells by degradation of the SlmA protein. This protein, together with the nucleoid, prevents the placement of the septum in the regions occupied by the chromosome by a mechanism called nucleoid occlusion (NO). A second septum placement mechanism, the MinCDE system (Min) involving a pole-to-pole oscillation of three proteins, nonetheless remains active in maxicells. Both Min and NO act on the polymerization of FtsZ, preventing its assembly into an FtsZ-ring except at midcell. Our results show that even in the total absence of NO, Min oscillations can direct placement of FtsZ in maxicells. Deletion of the FtsZ carboxyl terminal domain (FtsZ*), a central hub that receives signals from a variety of proteins including MinC, FtsA and ZipA, produces a Min-insensitive form of FtsZ unable to interact with the membrane-anchoring FtsA and ZipA proteins. This protein produces a totally disorganized pattern of FtsZ localization inside the maxicell cytoplasm. In contrast, FtsZ*-VM, an artificially cytoplasmic membrane-anchored variant of FtsZ*, forms helical or repetitive ring structures distributed along the entire length of maxicells even in the absence of NO. These results show that membrane anchoring is needed to organize FtsZ into rings and underscore the role of the C-terminal hub of FtsZ for their correct placement.

Discussion Points

  • Was the paper clearly written, presented etc. Did it all make sense?
  • Were the methods sound? Was there anything extra that you would have done? How were the stats?
  • Were the conclusions supported by the results?
  • How much of this is new? What are the practical implications?
  • What experiments would you do next?
  • Hope to see you on Tuesday 1st April, 8pm BST 🙂  (thats right! our clocks will have changed and we’ll be on summer time!)