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12-13_Microbial_Growth___Metabolism_Combo

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Unformatted text preview: From the Virtual Microbiology Classroom on ScienceProfOnline.com Bacterial Population Growth Curve Image: Bacterial growth phases , Michal Komorniczak From the Virtual Microbiology Classroom on ScienceProfOnline.com Generation Time Under Optimal Conditions (at 37 o C) Organism Generation Time Bacillus cereus 28 min Escherichia coli 12.5 min Staphylococcus aureus (causes many types of infections) 27-30 min Mycobacterium tuberculosis (agent of Tuberculosis) 18 – 24 hrs Treponema pallidum (agent of Syphilis) 30 hrs Images: B. cereus, E. coli & S. aureus by T. Port; TB culture , Dr. George Kubica PHIL #4428, Treponema pallidum , Dr. Edwin P. Ewing, Jr., PHIL #836 From the Virtual Microbiology Classroom on ScienceProfOnline.com Meet the Microbe! _______________ “ GRAM-POSITIVE” Bactera Q: Why is “ Gram-positive ” in quotation marks? Genus of rod-shaped, acid-fast bacteria . Mycolic acid in cell wall gives Mycobacteria many characteristics that defy medical treatment, including:  increased resistance to chemical damage & dehydration  allows the bacterium to grow inside macrophages, hiding it from host's immune system M. tuberculosis doubles population every 18-24 hours, while M. leprae doubles population about every 14 days. Extremely long generation time; contributes to the chronic nature of both diseases. Mycolic Acid, Generation Time & Disease Images: TB Culture, PHIL #4428; Acid fast stain, Mycobacteria pink, T. Port TB Culture Acid-fast stain From the Virtual Microbiology Classroom on ScienceProfOnline.com Factors Influencing Microbial Growth • Nutrition • Oxygen • Temperature • pH • Osmotic Pressure This scanning electron micrograph (SEM) depicts numerous clumps of methicillin-resistant Staphylococcus aureus bacteria, commonly referred to by the acronym, MRSA, by Janice Haney Carr, PHIL #10046 From the Virtual Microbiology Classroom on ScienceProfOnline.com Microbial Nutrition • Organisms use a variety of nutrients for: – their energy needs – to build organic molecules & cellular structures. • Most common nutrients contain necessary elements: – ______ – Oxygen – Nitrogen – Hydrogen • These 4 elements make up 95% of dry weight of bacterium. • The other 5% is composed of Calcium, Copper, Iron, Magnesium, Manganese, Phosphorus and Iron. • Other elements that are needed are ___________ __________. • These elements are needed in extremely small amounts, can be obtained through water intake. Image: Salmonell a, Rocky Mountain Labs NIAID NIH From the Virtual Microbiology Classroom on ScienceProfOnline.com • Obligate ____________ – Need oxygen to stay alive. Aerobic respiration = Use of O2 to break down food into useable energy....
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