Lab 28: Temperature: Effects on Growth
What is the optimum growth temperature for most human pathogens? Explain.
37C is the optimum temperature for most human pathogens because that is the human body temperature.
A. What is the estimated optimum growth temperature for Serratia marcescens? B. What is the estimated optimum growth temperature for Escherichia coli?
A. The estimated optimum growth temperature for Serratia marcescens is approximately 26C, as that is the peak of S. marcescens on the graph. B. The estimated optimum growth temperature for Escherichia coli is approximately 41C, as that is the peak of E. coli on the graph.
Psychrotrophs
Bacteria that are capable of surviving or even thriving in the extremely cold environment. They provide an estimation of the product's shelf life, also they can be found in soils, in surface and deep-sea waters, in Antarctic ecosystems, and in foods.
Name three cellular components involved in metabolism that is influenced by temperature changes.
Enzymes, cell membranes and transport, ribosomes
Hyperthermophiles
Growth optimum above 80C; many Archaea occupy environments that are heated by the volcanic activity where water is superheated to above 100C. These organisms have been isolated from thermal vents deep within the ocean floor and from volcanic heated hot springs.
Mesophiles
Optimal Growth between 20C and 50C. Includes most bacteria; most pathogens grow between 35C and 40C.
Psychrophiles
Optimal growth between -5C and 20C. Can be found in supercooled waters of the Arctic and Antarctic.
Thermophiles
Optimal growth between 50C and 80C. Bacteria in this group include soils where the midday temperature can reach greater than 50C or in compost piles where fermentation activity can cause temperatures to exceed 60-65C.
Differentiate between psychrophile and psychrotroph.
Psychrophile - typically found in supercool waters Psychrotroph - mesophilic bacteria that can grow are 4C causing food spoilage
Which temperature seems to be closest to the optimum temperature for pigment formation in Serratia marcescens?
The temperature that seems to be closest to the optimum temperature for pigment formation in Serratia marcescens is approximately 25C.
Why are psychrotrophic bacteria of concern to those in the food-service industry?
They are involved in food spoilage at refrigerator storage temperatures.
