Molecular and structural mechanisms of cell division site recognition in Bacillus subtilis

Barák I.¹, K. Muchová¹, N. Pavlendová¹, P. Florek¹, N. Pavlendová¹, J. Jamroškovič¹, Anthony J. Wilkinson², Ľ. Vávrová¹ and
S. Rešetárová¹

¹Institute of Molecular Biology, Slovak Academy of Sciences, Bratislava

²Department of Chemistry, University of York, York, UK

Bacillus subtilis is an internationally-recognised model organism, whose physiology, biochemistry and genetics has been studied for many years. Our research is oriented toward studying the proteins involved in basic processes in Bacillus subtilis as cell division, sporulation and programmed cell death.

Probably the most controversial question regarding cell division of rod-shaped bacteria concerns the mechanism that ensures correct placement of the division septum. At least two distinct mechanisms contribute to placement of the division machinery: the Min system and nucleoid occlusion. The fluid mosaic model of membrane structure has been revised in recent years as it has become evident that domains of different lipid composition are present in eukaryotic and prokaryotic cells. Using membrane binding fluorescent dyes, we demonstrate the presence of lipid spirals extending along the long-axis of cells of the rod-shaped bacterium B. subtilis. These spiral structures are absent from cells in which the synthesis of phosphatidylglycerol is disrupted suggesting an enrichment in anionic phospholipids. Green fluorescent protein fusions of the cell division protein MinD from B. subtilis also form spiral structures and these were shown by fluorescence resonance energy transfer (FRET) to be coincident with the lipid spirals. These data indicate a higher level of membrane lipid organization than previously observed and a primary role for lipid spirals in determining the site of cell division in bacterial cells. Little is known however of the origin of these spiral structures. In our current work we have focused on analyzing these lipid structures in correlation with other previously observed helical structures in the cell membrane or its close proximity.

Acknowledgements

This work was supported by the grant APVT-51-027804, No. ESF-EC-0106, LPP-0218-06 and VEGA grant 2/7007/27 from the Slovak Academy of Sciences and The Wellcome Trust Grant 082829/Z/07/Z.