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Mechanisms of Bacterial Cell Division; Implications for Deposition of the Complement Membrane Attack Complex

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Mechanisms of Bacterial Cell Division; Implications for Deposition of the Complement Membrane Attack Complex Mechanisms of bacterial cell division; implications for deposition of the complement membrane attack complex Erinke van Grinsven Master student “Infection and Immunity” Under supervision of drs. Evelien Berends Medical Microbiology, UMC Utrecht January 2012 Microscopic photograph title page: Courtesy of Evelien Berends. MAC deposition on dividing Streptococcus pyogenes cell. Green = antibody against the MAC Red = membrane dye 2 Contents Chapter 1: Introduction ........................................................................................................................... 4 Chapter 1a: Introduction to the bacterial cell wall ................................................................................. 4 Gram-positive versus Gram-negative bacteria .................................................................................... 4 Peptidoglycan structure ...................................................................................................................... 6 Peptidoglycan synthesis ...................................................................................................................... 6 Interspecies differences in peptidoglycan structure ........................................................................... 8 Visualization of peptidoglycan synthesis ............................................................................................. 8 Chapter 1b: Introduction to the human complement system ................................................................ 8 Chapter 2: Bacillus subtilis ..................................................................................................................... 11 Bacterial shape and orientation of the division plane ...................................................................... 11 Lateral cell wall synthesis .................................................................................................................. 11 Chromosome segregation ................................................................................................................. 12 Z ring formation and regulation ........................................................................................................ 13 Assembly of the division machinery .................................................................................................. 14 Formation of the division septum ..................................................................................................... 15 Separation ......................................................................................................................................... 15 Chapter 3: Staphylococcus aureus ......................................................................................................... 17 Bacterial shape and orientation of the division plane ...................................................................... 17 Chromosome segregation and Z ring formation and regulation ...................................................... 17 Assembly of the division machinery .................................................................................................. 18 Formation of the division septum ..................................................................................................... 19 Separation ......................................................................................................................................... 21 Chapter 4: Streptococcus pyogenes ...................................................................................................... 22 Bacterial shape and orientation of the division plane ...................................................................... 22 Lateral cell wall synthesis .................................................................................................................. 22 Z ring formation and regulation ........................................................................................................ 23 Formation of the division septum ..................................................................................................... 23 Separation ......................................................................................................................................... 23 Chapter 5: Escherichia coli, the Gram-negative model ......................................................................... 24 Elongation of the cell wall ................................................................................................................. 24 Chromosome segregation ................................................................................................................. 25 Z ring formation and regulation ........................................................................................................ 25 Assembly of the division machinery .................................................................................................. 27 Formation of the division septum and membrane constriction ....................................................... 27 Separation ......................................................................................................................................... 27 Chapter 6: Sporulation .......................................................................................................................... 29 Replication and Z ring formation during sporulation ........................................................................ 29 Formation of the sporulation septum ............................................................................................... 29 Chromosome segregation ................................................................................................................. 30 Engulfment ........................................................................................................................................ 30 Formation of the spore cortex .......................................................................................................... 31 Membrane fusion and separation ..................................................................................................... 32 Formation of the spore coat.............................................................................................................. 32 Chapter 7: Implications for MAC deposition ......................................................................................... 33 Bacillus subtilis .................................................................................................................................. 33 Staphylococcus aureus ...................................................................................................................... 34 Streptococcus pyogenes .................................................................................................................... 36 Physiological relevance of MAC deposition on Gram-positive bacteria ........................................... 36 References ............................................................................................................................................. 37 3 Chapter 1: Introduction This thesis discusses the cell wall structure of Gram-positive bacteria during the division cycle and aims to correlate this to site-specific binding of the membrane attack complex (MAC or C5b-9) of the human complement system. Experimental results demonstrating binding of fully assembled MAC to selected Gram-positive bacteria provided the basis for this review (E. Berends, unpublished results). Since Gram-positive bacteria are considered to be resistant to MAC-mediated lysis due to their thick peptidoglycan layer, this association was highly unexpected. More striking was that the MAC was deposited on specific sites on the cell surface, i.e. the divisional septum (Streptococcus pyogenes) or the cell poles (Bacillus subtilis). As the central complement protein C3b was found to cover the entire bacterial surface, the terminal pathway leading to MAC deposition could be initiated dispersedly (E. Berends, unpublished results). Nevertheless, the MAC only remained at these specific sites. To be able to better understand why the MAC is deposited on Gram-positive bacteria and what determines its location, this thesis will cover cell wall structure during division and sporulation of Gram-positive bacteria. This thesis aims to give a compact overview of the mechanisms of cell division of three important Gram-positive species: Bacillus subtilis, Staphylococcus aureus and Streptococcus pyogenes (Group A Streptococcus). Cell division of Escherichia coli will be discussed to highlight similarities and differences between Gram-positive and Gram-negative bacteria. Finally, I will discuss the implications for binding of the complement MAC to these Gram-positive bacteria. Chapter 1a: Introduction to the bacterial cell wall Gram-positive versus Gram-negative bacteria The inner contents and the cytoplasmic membrane are similar in all bacteria. Based on what is on the outside of the cell membrane, bacteria can be divided into two major classes. The Gram staining, published in 1844 by Hans Christian Gram, classifies almost all bacterial species as either Gram-negative or Gram-positive. Bacteria from both classes own an extracellular layer of peptidoglycan polymers, which is essential for replication, shape and survival. Peptidoglycan (PG) consists of polysaccharides linked Figure 1: General structure
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