Final answer:
Bacteria isolated from a hot tub at 39 °C are likely to be mesophiles, as they thrive at moderate temperatures which include the range of a hot tub's temperature.
Step-by-step explanation:
Bacteria isolated from a hot tub at 39 °C are most likely to be mesophiles. Mesophiles are organisms that thrive at moderate temperatures and have an optimal growth range between 20-45 °C. The 39 °C temperature of a hot tub falls within this range. These bacteria are commonly found in environments such as the human body, where the internal temperature is close to 37 °C, and in temperate and tropical environments where such temperatures are common. Examples of mesophiles include many of the common bacteria such as E. coli and Staphylococcus aureus.
In contrast, thermophiles are adapted to much higher temperatures, typically ranging from 50 °C to 80 °C, and would not be the primary type found at 39 °C. Hyperthermophiles, which grow best at temperatures above 80 °C, and psychrophiles, which prefer temperatures of 15 °C or lower, would not thrive in the conditions of a hot tub at 39 °C either.