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Unformatted text preview: Chapter 5 - Environmental Influences and Control of Microbial Growth Environmental factors that affect microbial growth Temperature Pressure Osmolarity pH Oxygen Temperature Temperature is a major environmental factor controlling microbial growth. ___________________ temperatures- minimum, optimum, & maximum temps for an organism ____________________ temperature - cellular processes _____________; cytoplasmic membranes stiffen ____________________ temperature- proteins start to __________________ ____________________ temperature- organism grows best; between min & max Microorganisms can be grouped by the temperature ranges they require. Cold: OC20C 20C45C 40C80C Extreme thermophiles 65C113C Psychrophiles- found in Example: Chlamydomonas- Molecular adaptations of psychrophiles: Membranes have _______________ ________________ compared to mesophiles or thermophiles _________________ can be used to preserve microbial cultures at ___________ _______________ (Dimethylsulfoxide) & ___________________ are commonly used in laboratories to preserve microbial cultures for long time in freezers. Mesophiles- Found in ____________________________ & many terrestrial & aquatic environments. Examples- most organisms you are familiar with such as Escherichia coli (found in the Thermophiles Optimum temp above Some ____________ have been found growing at temps above Places thermophiles are found: soils subjected to Thermus aquaticus is a common hot spring thermophile. The heat stable DNA polymerase from this bacterium is mass produced and used in laboratories to replicate DNA in a test tube. Molecular adaptations of thermophiles: Membranes have a _________________ are heat stable- __________________________________ compared to mesophiles or psychrophiles Heat shock response Occurs at high end of temperature range Help keep proteins from Induced by many Heat High salt concentrations Arid conditions Pressure Adapted to Up to 1,000 atm ____________________ organisms Grow at...
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- Spring '07