bacterial cell division

bacteria reproduce by binary fission , which is a single cell, divides into two identical daughter cells. it occurs through formation of the Z ring that recruits additional proteins to form the septa ring.

1. BACTERIAL CELL DIVISION SUBMITTED BY : Shubhangi kansal Submitted to : dr. dhuni chand m.sC . Microbiology 1 st semester

2. REPRODUCTION All types of macromolecules double in amount Proteins RNA and DNA Lipids for membranes Cell wall components Small organic and inorganic molecules In general, the materials are evenly distributed to each daughter cell. Each daughter cell contains : ½ old cell material & ½ new cell material All biosynthetic events must be carefully coordinated .

3. CELL DIVISION CELL DIVISION is pre programmed in 3- dimensions. It occurs in a spatial & temporal context: DNA repicates Formation of the FtsZ ring and cell elongation DNA partitions aided by Divisome A cell septum forms The daughter cells then separate

4. BACTERIAL CELL DIVISON OCCUR BY “BINARY FISSION ” In a growing rod shaped cell, elongation continues until the cell divides into two new cells; called BINARY FISSION . Cells elongate to approximately twice their original length & then forms a partition (SEPTUM) that separates the cell into two daughter cells. Results from the inward growth of the cytoplasmic membrane & cell wall from opposite directions, which continues until the two daughter cells pinched off. When one cell divides to form two, one generation has occurred, & the time required for this process is called the GENERATION TIME.

5. THE DIVISOME Several essential proteins play roles in cell division in Bacteria. Collectively, these proteins are called Fts proteins and a key one, FtsZ , plays a crucial role in binary fission. Fts proteins interact in the cell to form a division apparatus called the divisome . Fts stands for F ilamentous T emperature S ensitive .

6. The FtsZ ring appears & disappears during cell division

7. MinCD & nuclear occlusion act together to prevent Z-ring assembly midcell Cell elongation & nucleoid segregation alleviate nucleoid occlusion. Min C is recruited to the membrane by MinD . Membrane localisation of Min C is necessary for FtsZ inhibition to occur. Min E is responsible for keeping the MinCD complex from acting in the midcell region, thus enabling the formation of Z-ring in the proper location. Min E oscillates from pole to pole , keeping the zone of MinCD inhibition at the poles, & not at midcell .

8. MinD oscillation in E.coli allows formation of Z-ring in the center of the cell

9. Divisome and Cell Division

10. PEPTIDOGLYCAN SYNTHESIS Synthesis of new peptidoglycan during growth requires the controlled cutting of preexisting peptidoglycan along with the simultaneous insertion of peptidoglycan precursors. A lipid carrier molecule called bactoprenol plays a major role in the latter process. Bactoprenol is a hydrophobic C55 alcohol that is bonded to an N- acetylglucosamine /N- acetylmuramic acid/ pentapeptide peptidoglycan precursor. BACTOPRENOL transports peptidoglycan precursors across the cytoplasmic membrane by rendering them sufficiently hydrophobic to pass through the membrane. Once outside the cell, the bactoprenol complex interacts with enzymes called transglycosylases that insert peptidoglycan precursors into a growing point in the cell wall and catalyze glycosidic bond formation. Prior to this, small gaps in the existing peptidoglycan are made by enzymes called autolysins , New cell wall material is then added across the gaps . Peptidoglycan synthesis must be a highly coordinated process and peptidoglycan precursors must be readily available during autolysin activity. This is because tetrapeptide units must be spliced into existing peptidoglycan immediatelyafter autolysin activity in order to prevent a breach in the peptidoglycan at the splice point; a breach could cause spontaneous cell lysis , called autolysis .

11. REFERENCES BROCK BIOLOGY OF MICROORGANISMS by Madigan Martinko Dunlap Clark (Pearson Internatinal Edition)