Temperature Requirements for Microbial Growth - Online Tutor, Practice Problems & Exam Prep

Microbial growth is influenced by temperature, categorized into cardinal temperatures: minimum, optimal, and maximum. Microbes are classified into five groups based on their growth temperatures: psychrophiles thrive in cold (−10°C to 15°C), psychrotrophs in cool (−10°C to 35°C), mesophiles at moderate (10°C to 40°C), thermophiles in hot (40°C to 80°C), and hyperthermophiles in extreme heat (70°C to 120°C). Understanding these classifications aids in comprehending microbial ecology and their applications in various environments.

Temperature Requirements for Microbial Growth

In this video, we're going to begin our lesson on temperature requirements for microbial growth. As you may already know, different microbial species have specific temperature ranges in which these microbes are able to grow. These temperature ranges include minimum and maximum growth temperatures. If the temperatures are too cold or if the temperatures are too hot, then the microbes may not be able to grow. Cardinal temperatures refer to characteristic temperature values that define the specific temperature ranges in which a microbe can actually grow. The cardinal temperatures include a minimum temperature, which is the lowest possible temperature that an organism can actually grow at. Usually, the minimum temperature is not associated with the best growth. It will usually be some form of ineffective growth at the minimum temperature. Then there is the optimal temperature, which is the best temperature for an organism to grow, where the organism is able to multiply and grow most rapidly. The optimal temperature is the temperature that is best suited for that particular organism. The cardinal temperatures also include a maximum temperature, which, of course, is the highest temperature that an organism can grow at. The maximum temperature typically only allows for ineffective growth.

If we take a look at our image down below, we can get a better understanding of cardinal temperatures, which again include a minimum temperature, an optimal temperature, and a maximum temperature. Notice that in this graph that we have down below on the left-hand side, we're showing you the cell growth rate. Having a low value on this y-axis means that the cells are growing really slowly and so they're not growing very well. However, having a high value on the y-axis corresponds with high cell growth, and the cells are able to grow at a very fast rate. Notice that down below what we have is the specific temperature. This curve has a shape that somewhat resembles a bell curve. The minimum temperature is the coldest possible temperature that will allow for cell growth, but note that the cell growth is not going to be very effective at the minimum temperature in most cases. Somewhere in between the minimum temperature and the maximum temperature is the optimal temperature. The optimal temperature is the specific temperature value that allows for the highest amount of growth, the highest growth rate. Over here what we have is the maximum temperature, which is the highest possible temperature that allows for cell growth. Once again, in most cases, the maximum temperature does not allow for very effective cell growth. This concludes our lesson on temperature requirements for microbial growth, and we'll be able to get some more practice applying these concepts and learn more about microbial growth as we move forward in our course. So, I'll see you in our next video.

Which bacterial culture will have the highest growth rate?

• A. E. coli bacteria being grown between the temperatures of 37°C & 40°C (optimal temperatures).
• B. E. coli bacteria being grown between the temperatures of 15°C & 20°C (minimum temperatures).
• C. E. coli bacteria being grown at 45°C (maximum temperature).
• D. E. coli bacteria would grow at the same rate at any temperature.

Classification of Microbes by Growth Temperature

In this video, we're going to begin our lesson on the classification of microbes by growth temperature. And so microbes are actually classified into 5 groups based on their cardinal temperatures, which recall from our last lesson video is referring to the growth temperatures. From the minimum growth temperature up to the maximum growth temperature for these cells to survive. And so if we take a look at this image down below, notice that we're showing you a graph where on the y-axis it has the cell growth rate where the higher the y-axis is the higher the rate of growth for those cells. And the lower the y-axis is, the lower the growth rate is for those cells. And then on the x-axis, what we have is the temperature in degrees Celsius, increasing from left to right. And so notice that we have these 5 different curves here in this graph where each of these curves corresponds to a different group of microbes. And so the first group of microbes that we have is the one that's on the far left over here in light blue, which is referring to the psychrophiles. And so "psycho" is actually a root that means cold, and "phile" is a root that means loving. And so these are organisms that love extremely cold temperatures. And so you can see that they can thrive from temperatures anywhere between negative 10 degrees Celsius and about 15 degrees Celsius. And the optimum growth rate is going to be at a temperature somewhere between 0 and 10 degrees Celsius. And so these psychrophiles really, really do grow best in really cold environments, such as, for example, icebergs. Now the next group that we have here is the one in green, which is referring to the psychrotrophs. And once again, "psycho" is a root that means cold, and "troph" is actually a root that's referring to nutrients. And so this can help remind you of refrigerators since refrigerators store a lot of the nutrients that you and I consume. And so these psychrotrophs tend to live inside of cool temperatures. And they can survive from temperatures anywhere between negative 10ish degrees Celsius all the way up to about 35 degrees Celsius. But notice that the optimum growth temperature for these psychrotrophs is somewhere between 20 and 30 degrees Celsius. And so they survive in cool environments, like, again, refrigerators. Now the next group that we have here is the one here in purple which is referring to the mesophiles. And so as this scientist here is saying, mesophiles grow on me. And so humans have body temperatures right around 35ish degrees Celsius. And so notice that the optimum growth temperature for these mesophiles is right around 35ish degrees Celsius. And so these mesophiles can survive anywhere from between 10 degrees Celsius up to over 40 degrees Celsius. But once again, mesophiles are gonna be somewhat in the middle here, and they are the middle group, for these 5 groups that we see here. Now the next group that we have here is the curve that is here in orange which is referring to the thermophiles. And thermophiles survive in much warmer and hotter temperatures such as hot springs, for example. And thermophiles can survive from anywhere between 40 degrees Celsius up to over 80 degrees Celsius, but the optimum growth temperature is pretty high somewhere around 70 degrees Celsius or so. Then, the last group that we have here is the one that is in dark red over here, which is referring to the hyperthermophiles. And so "hyper" is a root that's referring to very high. And so, hyper thermophiles can survive in extreme amounts of heat. And so notice that they can survive in temperatures from about 70ish to 75ish degrees Celsius all the way up to about 120 degrees Celsius. And notice that their optimal growth temperature is extremely high, right around 100 degrees Celsius. And so these hyperthermophiles can survive in hydrothermal vents deep underneath the ocean where the temperatures are extremely hot. And so these are the 5 classes of microbes that are grouped based on their growth temperatures: the psychrophiles, the psychrotrophs, the mesophiles, the thermophiles, and the hyperthermophiles. And so we'll be able to get some practice applying these concepts as we move forward in our course. So I'll see you all in our next video.

What is the optimum growth temperature of mesophiles?

• A. 0-10 °C.
• B. 0-20 °C.
• C. 20-30 °C.
• D. 50-60 °C.

A thermophile or a hyperthermophile species would have thermo-stable proteins & enzymes that…

• A. Resist denaturation in extremely high temperatures.
• B. Perform more efficiently in cool temperatures.
• C. Easily denature in extremely high temperatures.
• D. Have a particular amino acid sequence that restricts bond formation.

How to Memorize the Classification of Microbes by Growth Temperatures

In this video, we're going to talk about a silly way to help you guys memorize the classification of microbes by growth temperatures, from the lowest growth temperature to the highest growth temperatures. Recall from our previous lesson videos that psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles are those five groups of microbes organized by their growth temperatures. Recall that psychrophiles grow at the coldest temperatures, whereas hyperthermophiles grow at the hottest growth temperatures.

Really, all you need to do to remember the order of these five groups is to remember the following phrase, which is "Psycho Phil psyched my temperate horse." Notice that we've got Psycho Phil over here saying he's crazy, and notice he's in the cold temperatures. He's psyching out this horse over here. Notice he's like, "ah." He is a temperate horse here clearly with this thermometer trying to cool down his temperatures.

If you can remember "Psycho Phil psyched my temperate horse," then that could help you remember that psychrophiles are going to be the coldest, followed by psychrotrophs. Then we have mesophiles, then thermophiles, and last but not least, what we have are the hyperthermophiles.

Once again, this is just a silly way that could possibly help you memorize the order of these groups from lowest to highest growth. This here concludes our brief lesson on this, and we'll be able to get some practice as we move forward. So, I'll see you all in our next video.

The temperature of a human body is anywhere from 35-40C. What type of pathogen can infect humans?

• A. Thermophile.
• B. Hyperthermophile.
• C. Psychrophile.
• D. Mesophile.

Here’s what students ask on this topic:

What are the cardinal temperatures for microbial growth?

Cardinal temperatures refer to the characteristic temperature values that define the specific ranges in which a microbe can grow. These include the minimum, optimal, and maximum temperatures. The minimum temperature is the lowest temperature at which an organism can grow, but growth is usually ineffective. The optimal temperature is the best temperature for growth, where the organism multiplies most rapidly. The maximum temperature is the highest temperature at which an organism can grow, but growth is typically ineffective at this point. Understanding these temperatures helps in studying microbial ecology and their applications in various environments.

How are microbes classified based on their growth temperatures?

Microbes are classified into five groups based on their growth temperatures: psychrophiles, psychrotrophs, mesophiles, thermophiles, and hyperthermophiles. Psychrophiles thrive in extremely cold temperatures (−10°C to 15°C). Psychrotrophs grow in cool environments (−10°C to 35°C). Mesophiles prefer moderate temperatures (10°C to 40°C), which include human body temperature. Thermophiles thrive in hot environments (40°C to 80°C), such as hot springs. Hyperthermophiles can survive in extreme heat (70°C to 120°C), like hydrothermal vents. These classifications help in understanding microbial ecology and their applications in various environments.

What is the optimal temperature for mesophiles?

The optimal temperature for mesophiles is around 35°C. Mesophiles are microbes that thrive in moderate temperature ranges, typically between 10°C and 40°C. This group includes many human pathogens and microbes that inhabit the human body, as the human body temperature is approximately 37°C. Understanding the optimal temperature for mesophiles is crucial for studying human-related microbial activities and infections.

Why is it important to understand the temperature requirements for microbial growth?

Understanding the temperature requirements for microbial growth is crucial for several reasons. It helps in identifying the optimal conditions for culturing microbes in laboratory settings, which is essential for research and industrial applications. It also aids in controlling microbial growth in food preservation, medical sterilization, and environmental management. Additionally, knowing the temperature preferences of different microbes can help in understanding their ecological roles and how they adapt to various environments, from extreme cold to extreme heat.

What environments do hyperthermophiles thrive in?

Hyperthermophiles thrive in extremely hot environments, with temperatures ranging from 70°C to 120°C. Their optimal growth temperature is around 100°C. These microbes are often found in hydrothermal vents deep under the ocean, hot springs, and other geothermal areas. Their ability to survive and grow in such extreme conditions makes them of particular interest in studies of extremophiles and potential applications in biotechnology, such as in the development of heat-stable enzymes.