Chapter 6 - Microbial growth

Chapter 6 - Microbial growth - C hapter 6 (Tortora)...

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Chapter 6 (Tortora) Microbial Growth CHAPTER 6 Microbial Growth What is Growth? Growth is an increase in cell numbers. An increase in cell mass does not necessarily signify growth; it may be due to increase in the number of inclusion bodies. Bacterial growth takes place through binary fission. A. The parent cell enlarges. B. Chromosome (DNA) duplicates. C. A central transverse septum forms that divides the cell into two daughter cells. Some microorganisms grow by budding or by fragmentation. Generation Time: The time required for the cell population to double. 1 2 4 8 16 Parent First Second Third Fourth Physical Requirements for Growth: 1. Temperature A. Minimum growth temperature B. Optimum growth temperature C. Maximum growth temperature Microorganisms can be classified into three major groups on the basis of temperature range. 1
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1. Psychrophiles (cold-loving) 2. Mesophiles (moderate temp. loving 3. Thermophiles (heat-loving) Temperature (ºC) Min Opt Max 1. Psychrophiles 0 15 20 2. Mesophiles 25 37 40 3. Thermophiles 40 50-60 85 2. pH The degree of acidity or alkalinity of a solution. Or A measure of hydrogen ion concentration of a solution. A. Acidophiles PH range: 1----------6.0 Examples: a. Bacteria: • Sulfolobus acidocaldarium • Helicobacter pylori b. Algae: • Cyanidium caldarium and c. Most Fungi B. Neutrophiles pH range: 6.5 --------- 7.5 Examples: E. coli S. aureus 2
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C. Alkalophiles PH range: 8.0 -------- 11.0 Example: Alcaligenes faecalis Bacillus alkalophile Buffer: any substance that prevents extreme pH changes. Example: Potassium Phosphate 3. Osmotic Pressure Osmophiles (halophiles and saccharophiles are organisms that can tolerate high solute concentration in their environment. A. Facultative halophile Organisms that do not require high salt concentration but can tolerate it. Example:
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This note was uploaded on 09/24/2011 for the course MCB MCB2010 taught by Professor Smith during the Fall '09 term at Broward College.

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Chapter 6 - Microbial growth - C hapter 6 (Tortora)...

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