PART II: Effects of temperature on growth Agitate tubes before interpreting; In the table below, record growth results as: (++ = very turbid; + = turbid; "-" = no growth) Temperature Serratia marcescens Geobacillus stearothermophilus 4°C - - 10°C + - 28°C + - 37°C ++ ++ 45°C - - 65°C - - 6. Describe the results of the Serratia marcescens demo plate images, incubated at 2 different temperatures (28°C and 37°C), focusing on the color of the growth. Why would pigmentation appear only at certain temperatures in Serratia cultures? 7. Based on the 4°C (refrigerator) results, why do we refrigerate food? 8. Based on your results, to what temperature category do each of the above bacteria belong? A. Serratia marcescens: B. Geobacillus stearothermophilus: Biology 15 15.19
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Step 2: We refrigerate food to slow down the growth of bacteria and other microorganisms that can cause food spoilage and foodborne illnesses. The low temperature of the refrigerator inhibits the growth of bacteria, helping to keep food fresh for a longer period Show more…
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Microbial growth favors different temperature. Define the following temperature preference: Grows best at... Will not grow at... Additional information? Psychrophile, Psychrotroph, Mesophile, Thermophile.
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To investigate the effect of temperature on bacterial growth, cultures of Bacillus cereus, Enterococcus faecalis and Escherichia coli were prepared at 20°C, heated for 30min at 60°C and then for a further 10min at 100°C. Samples were taken at each temperature and streaked onto nutrient agar and incubated overnight at 30°C. The following results were obtained, where +++ represents heavy growth, ++ for reasonable growth, + for slight growth and – for no growth. 20°C 60°C 100°C B. cereus +++ +++ + Ent. faecalis +++ ++ – E. coli +++ + – What can you conclude from these results about the microorganisms tested in terms of their tolerance to heat?
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