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The actin homologue MreB organizes the bacterial cell membrane

The actin homologue MreB organizes the bacterial cell membrane. Strahl , Burmann , & Hamoen Nature Comm. 2014. Basics of Lipids & Bilayers. Basics of Lipids & Bilayers. Basics of Lipids & Bilayers. Basics of Lipids & Bilayers. Basics of Lipids & Bilayers. Basics of Lipids & Bilayers.

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The actin homologue MreB organizes the bacterial cell membrane

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  1. The actin homologue MreB organizes the bacterial cell membrane Strahl, Burmann, & HamoenNature Comm. 2014

  2. Basics of Lipids & Bilayers

  3. Basics of Lipids & Bilayers

  4. Basics of Lipids & Bilayers

  5. Basics of Lipids & Bilayers

  6. Basics of Lipids & Bilayers

  7. Basics of Lipids & Bilayers

  8. Basics of Lipids & Bilayers Membrane proteins can induce a phase separation by membrane thickness or morphology

  9. The Initial Observation uniform? correlated?

  10. How much should you trust a label? Especially a non-specific, mobile, unregulated lipid label? How does the protonation state change the dye? It could be that the hydrophobic matching is good between dye and Mre proteins. Is the protein conformation or binding partners the same with CCCP+ ? (probably not) Could that induce phase separation?

  11. What is CCCP? Carbonyl cyanide m-chlorophenylhydrazone: A chemical inhibitor of oxidative phosphorylation, destroys the proton gradient across the membrane.

  12. What is CCCP? Nigericin Carbonyl cyanide m-chlorophenylhydrazone: A chemical inhibitor of oxidative phosphorylation, destroys the proton gradient across the membrane. Monensin-A Valinomycin

  13. What does “organize” mean? spatial or temporal? lipid pair correlation functions? phase separation? correlations between shape and composition? specific protein associations? changes in lipid mobility / phase? changes in leaflet structure and asymmetry?

  14. Which proteins are ‘responsible’? ΔrodA

  15. Do lipid properties change? (post processing) No statistical or temporal analysis of RIF properties, in either channel, and no significance testing.

  16. Do lipid properties change? wt CCCP- wtGFP-mreB CCCP-

  17. Do lipid properties change? wt CCCP- wtGFP-mreB CCCP-

  18. Do lipid properties change? • No significance testing between these values. • Used Pearson CC, but did not allow for negative values. • Not clear how they went from images to intensities used in CC. • No demonstration of spectral independence.

  19. Do lipid properties change? wt CCCP- wtGFP-mreB CCCP-

  20. Let those without blame … p-values w/wo poles included in all data

  21. How do proteins respond?

  22. How do proteins respond? mreB + mreB -

  23. Does osmotic pressure matter?

  24. Does osmotic pressure matter? Membrane invagination is caused not only by plasmolysis. ATP synthase overproduction, Arechaga 2013. Maybe CCCP increase available area causing invagination and curvature mediate localization of lipids and MreB?

  25. Does osmotic pressure matter? Membrane invagination is caused not only by plasmolysis. CheA/CheW overproduction, E. coli, Zhang 2006. Maybe CCCP increase available area causing invagination and curvature mediate localization of lipids and MreB?

  26. Does osmotic pressure matter?

  27. My personal verdict. Correct small errors in image and data processing. Good genetics and imaging. Data supports thesis, but there are holes in the ultimate conclusion. Need to define “organization” better. Need to do in vitro or other studies of effects of ionophores on membrane area, bending stiffness, phase dynamics, before these results are in proper context. While the protein mobility and loci data are interesting, in their own right, they don’t necessarily indicate a change in membrane organization beyond simply the motion of MreB. A non-grade-inflated B-

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