Final answer:
Mesophiles are regarded as dangerous to humans because their optimal growth temperature coincides with the human body's temperature, making it easier for pathogenic mesophiles to grow and cause diseases. They typically thrive at temperatures between 20°C to 45°C.
Step-by-step explanation:
Mesophiles are organisms that thrive at moderate temperatures, typically between 20°C to 45°C. Mesophiles are considered the most dangerous to humans because pathogenic mesophiles have an optimal growth temperature of 37°C (98°F), which is the normal human body temperature. This means they can grow well inside human bodies and could potentially cause illness more easily compared to organisms preferring other temperature ranges. Mesophilic organisms are not only notable for their impact on human health but are also important in the production of various foods, such as cheese, yoghurt, beer, and wine, due to their ability to thrive within the same temperature range as these fermentation processes.