Lab Review
Chapter 11: Effect of Temperature on Microbial Growth
1. [CH-11-01] Group of prokaryotes called psychrophiles inhabit very cold regions of Earth and have growth temperature range between --5OC to +15OC with optimal growth temperature around +5OC to +10OC. How can these microbes grow at temperatures below 0OC, the water freezing point?
The microbes often have a high content of short, unsaturated fatty acids in their plasma membrane as well as antifreeze proteins to protect their DNA.
2. [CH-11-02] Psychrotrophic bacteria have growth temperature range between above 0OC to +30OC with optimal growth temperature around +20OC to +28OC. What is the importance of these microbes to human health?
Psychrotrophic bacteria are capable of growing in refrigerators leading to food spoilage in refrigeration units despite lower temperatures.
3. [CH-11-03] Mesophiles bacteria have growth temperature range between +15OC to +42OC with optimal growth temperature around +30OC to +37OC. What is the importance of these microbes to human health?
Most pathogens known to date are mesophiles because the range between 30ºC and 37ºC is within the human body temperature.
4. [CH-11-04] Thermophilic bacteria have growth temperature range between +40OC to +80OC with optimal growth temperature around +60OC to +68OC. What is the importance of these microbes to humans?
Thermophilic bacteria usually do not pose a major threat to humans because of their high optimal growth range. But they do provide useful enzymes that are heat resistant, allowing for their use in PCR reactions.
Thermophilic bacteria usually do not pose a major threat to humans because of their high optimal growth range. But they do provide useful enzymes that are heat resistant, allowing for their use in PCR reactions.
5. [CH-11-05] Compare obligate aerobes, facultative anaerobes, obligate anaerobes, microaerophiles, and aerotolerant anaerobes. Give example for each microbial group –
Obligate aerobes: Only grows in presence of O2; Mycobacterium tuberculosis
Facultative anaerobes: Grow better in O2, but can live without; Escherichia coli
Obligate anaerobes: Only grow without the presence of O2; Clostridium botulinum
Microaerophiles: Only grow in presence of small O2, 2%<x<10%; Helicobacter pylori
Aerotolerant anaerobes: Unaffected by O2 presence because of fermenters; Streptococcus pyogenes
6. [CH-11-06] What are the functions of superoxide dismutase and catalase in bacterial cell?
Superoxide dismutase: Breaks down superoxide (O2-) into O2 + H2O2.
Catalase: Breaks down hydrogen peroxide (H2O2) into O2 + H2O.
Superoxide dismutase: Breaks down superoxide (O2-) into O2 + H2O2.
Catalase: Breaks down hydrogen peroxide (H2O2) into O2 + H2O.
7. [CH-11-07] What is the purpose of growing bacteria in the candle jar? –
Candles provide a high amount of carbon dioxide in the environment for Capnophilic bacteria.
Bordetella: Obligate aerobe, 35ºC
Clostridium: Obligate anaerobe, 35ºC
Escherichia: Facultative anaerobe, 37ºC
Lactobacillus: Facultative anaerobe, 30-40ºC
Staphylococcus: Facultative anaerobe, 37ºC
Streptococcus: Aerotolerant, 35-37ºC
9. [CH-11-09] Describe morphology, cell grouping, oxygen and temperature requirements of Deinococcus radiodurans – coccus, tetrad group, obligate aerobe, optimal growth temperature 25-30ºC.
10. [CH-11-10] What are optimal temperature for growth of Escherichia coli, Geobacillus stearothermophilus, and Deinococcus radiodurans –
E. coli optimal temperature – 37ºC
G. stearothermophilus optimal temperature – 55ºC
D. radiodurans optimal temperature – 37ºC or 30ºC depends on what paper referred
E. coli optimal temperature – 37ºC
G. stearothermophilus optimal temperature – 55ºC
D. radiodurans optimal temperature – 37ºC or 30ºC depends on what paper referred
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