EXAM 2 NS - 1 9-18 Ch. 6 Microbial Growth Bacterial Cell...

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1 9-18 Ch. 6 Microbial Growth Bacterial Cell Division 6.1 Cell Growth and Binary Fission, p.136 Growth of most microorganisms occurs by the process of binary fission Fig. 6-1 1. DNA replication 2. Cell elongation 3. Septum formation - where the actual division takes place 4. Completion of septum with formation of distinct walls 5. Cell separation Every time one cell becomes two cells, one generation lapses. 6.2 Fts Proteins, the cell Division Plane, and Cell Morphology, p. 137 6.3 Peptidoglycan synthesis and Cell Division p. 139 For cell division: 1. DNA replication 2. Formation of divisome (division apparatus) FtsZ proteins form ring where cell begins division FtsA protein- an ATP hydrolyzing enzyme; provides energy for divisome assembly 3. Cell elongation FtsI protein – involved in peptidoglycan synthesis FtsK protein – a DNA translocase; moves DNA during cell division Fig. 6-2a Fig. 6-2b Prokaryotic “cytoskeleton” FtsZ protein structure similar to tubulin MreB protein struture similar to actin -forms filamentous spiraled bands around inside of cell under the cytoplasmic membrane -defines cell shape by exerting pressure outward (forces the weak spots to go out) -coccus shaped bacteria lack MreB gene Cell wall synthesis 1. autolysins create small openings in existing cell wall a. Autolysis (spontaneous cell lysis) may occur if there is an error in inserting new cell wall material 2. Formation of peptidoglycan precursors N-acetylgulcosamine/N-acetylmuramic acid/pentapeptide 3. Transport of pep. Precursors to expanding cell wall bactoprenol 4. Insertion of peptidoglycan precursors into existing wall transpeptidation
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2 Bactoprenol ( can go through cytoplasmic membrane very easily.) -hydrophobic lipid alcohol -binds the peptidoglycan precursor -facilitates transport through the cytoplasmic membrane - Fig. 6-5a Transpeptidation - peptide bond formation between pentapeptide of peptidoglycan precursor and tetrapeptide of an existing peptidoglycan unit Fig 6-5b Fig. 6-3 6.6 The Growth Cycle, p.142 Populations of microorganisms show a characteristic growth pattern when incoculated into a fresh culture medium Growth Phases: 1. lag phase- transition period to allow synthesis of enzymes for biosynthesis - accessing its environment and determine what enzymes need to be made - No growth takes place in this environment. 2. exponential phase- regularly dividing cells - Grows until it can’t anymore, until nutrients become limited or something is toxic. 3. stationary phase- essential nutrient depleted, toxic products build up, growth stops - endospores will be formed b/c of deficiency. 4. death phase- cells die Part II Growth of Bacterial Populations 6.4 Growth Terminology and the Concept of Exponential Growth p.140 Generation (doubling) time- time required for one cell to form two cells Exponential growth- growth pattern where number of cells doubles over a regular time interval - It takes about 5 hours to start to see the culture. Fig. 6-6a
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This note was uploaded on 03/30/2008 for the course BIOL 2051 taught by Professor Brininstool during the Fall '07 term at LSU.

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EXAM 2 NS - 1 9-18 Ch. 6 Microbial Growth Bacterial Cell...

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