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Med. Micro. 8:30AM, Wednesday 29 March 2006 Bacterial Growth, Nutrition and Death. Simon Silver e-mail: simon@uic.edu. Bacterial cell multiplication . Bacterial growth rate, k dB/dt = kB large k = fast growth; small k = slow growth Generation Time: doubling time, t D
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Med. Micro. 8:30AM, Wednesday 29 March 2006Bacterial Growth, Nutrition and Death Simon Silver e-mail: simon@uic.edu
Bacterial cell multiplication • Bacterial growth rate, k • dB/dt = kB • large k = fast growth; small k = slow growth • Generation Time: doubling time, tD • large tD = slow growth; small tD = fast growth
The growth curve • Lag phase • exponential phase: balanced growth • Stationery phase • Death • Bacterial cell cycle and cell division
Microbial death • Sterilization: total inactivation of all living organisms • Disinfection: killing organisms on a surface • Antiseptic: agent that kills or prevents growth, can be used on body surface • Bacteriostatic: reversibly inhibits bacterial multiplication • Bactericidal; irreversibly inhibits bacterial multiplication
Requirements for bacterial growth • Definition of growth • New “state”: VBNC- viable but not culturable • Nutritional requirements: water, carbon, nitrogen, phosphorous, sulfur
Bacterial growth • Physical requirements • pH • Temperature: Psychrophiles, Mesophiles- pathogens, Thermophiles • Salinity • Oxygen • Nutrients
Metabolism: generating energy and synthesizing macromolecules • Fermentation • Glycolytic pathway • Alternative fates of pyruvate
Respiration • aerobic respiration • molecular oxygen serves as the electron acceptor • Anaerobic respiration • Organic electron acceptors