Difference Between Psychrophiles and Psychrotrophs

The key difference between psychrophiles and psychrotrophs is that psychrophiles are microorganisms with an optimal growth temperature of 15 ⁰C or lower, a maximum temperature below 20 ⁰C, and a minimal growth temperature at 0 ⁰C or lower while psychrotrophs are microorganisms that can grow at 0 ⁰C but have an optimal temperature of 20-40 ⁰C.

The chemical and physical state of the environment greatly influences the growth of microorganisms. Temperature, pH, oxygen availability, water activity, light and pressure are some of these physiochemical factors that affect the microbial life. Microorganisms that inhabit extreme environments possess specific properties. For example, microbes that inhabit habitats that are very hot or very cold have specific properties. Psychrophiles and psychrotrophs are two groups of microorganisms that are able to grow at cold temperatures.

CONTENTS

1. Overview and Key Difference
2. What are Psychrophiles
3. What are Psychrotrophs
4. Similarities Between Psychrophiles and Psychrotrophs
5. Side by Side Comparison – Psychrophiles vs Psychrotrophs in Tabular Form
6. Summary

What are Psychrophiles?

Psychrophiles are microorganisms with an optimal growth temperature of 15 ⁰C or lower, a maximum growth temperature of 20 ⁰C or lower and a minimum growth temperature of 0 ⁰C or lower. They are present in environments that are constantly cold such as oceans with an average temperature of 5 ⁰C, sea ice, snowfields and glaciers and marine sediments, etc. Since psychrophiles are unable to survive at a temperature higher than 20 ⁰C, they may be killed by exposure to room temperature.

Psychrophiles produce enzymes that function optimally at cold temperatures. These cold-active enzymes show greater amounts of α-helix and lesser amounts of β-sheet secondary structure since β-sheet secondary structures tend to be more rigid than α-helices. Thus, the greater α-helix content of cold-active enzymes probably allows these proteins greater flexibility for catalyzing their reactions at cold temperatures. Cold-active enzymes also tend to have greater polar and lesser hydrophobic amino acid contents. Furthermore, they have lower numbers of weak bonds (hydrogen and ionic bonds) and fewer specific interactions between regions. All of these characteristics collectively increase the functionality of cold-active enzymes at low temperatures.

In addition, cytoplasmic membranes of psychrophiles tend to have a higher content of unsaturated fatty acids and shorter-chain fatty acids. This helps to maintain a semifluid state of the membrane at low temperatures. Another molecular adaptation of psychrophiles to cold temperature is “Cold-shock” proteins, which are able to maintain the functionality of other proteins in cold condition. Moreover, they produce cryoprotectants, including antifreeze proteins or specific solutes that help to prevent the formation of ice crystals that can damage the cytoplasmic membrane.

What are Psychrotrophs?

Psychrotrophs are the microorganisms that can grow at 0 ⁰C but have an optimal temperature of 20-40 ⁰C. They are more likely to be found in environments that are seasonally cold. Psychrotrophs are more abundant in nature than psychrophiles. Hence, they can be isolated from soils and water in temperate climates, as well as from meat, milk and other dairy products, cider, vegetables, and fruit stored at refrigeration temperatures. Moreover, although psychrotrophs grow at 0 ⁰C, most do not grow very well at that temperature.

Various bacteria, Archaea, and microbial eukaryotes are psychrotrophs. These microbes are the major food spoiling agents of refrigerated foods. Therefore, psychrotrophs are a major problem in the dairy industry.

What are the Similarities Between Psychrophiles and Psychrotrophs?

• Both psychrophiles and psychrotrophs are cold-loving microorganisms.
• They are extremophiles.
• Both can grow at 0 ⁰
• Furthermore, they are capable of enduring extended periods of cryobiosis.

What is the Difference Between Psychrophiles and Psychrotrophs?

Psychrophiles and psychrotrophs are two groups of cold-loving microorganisms. The key difference between psychrophiles and psychrotrophs is that psychrophiles are the microorganisms with an optimal growth temperature of 15 ⁰C or lower, a maximum growth temperature of 20 ⁰C or lower and a minimum growth temperature of 0 ⁰C or lower while psychrotrophs are the microorganisms that can grow at 0 ⁰C but have an optimal temperature of 20-40 ⁰C. Besides, the exposure to room temperature may kill psychrophiles while psychrotrophs do not die at room temperature. So, this is also a difference between psychrophiles and psychrotrophs.

Another difference between psychrophiles and psychrotrophs is that psychrophiles are found in constantly cold environments, while psychrotrophs are found in seasonally cold environments. Moreover, psychrophiles grow well at 0 ⁰C. Psychrotrophs also grow at 0 ⁰C, but they do not grow very well at that temperature like psychrophiles.

Summary – Psychrophiles vs Psychrotrophs

Psychrophiles and psychrotrophs are two types of microorganism groups that grow at cold temperatures. They are cold-loving extremophiles. Psychrophiles have the optimum temperature of 15 ⁰C or lower while psychrotrophs have an optimal temperature of 20-40 ⁰C. Furthermore, psychrophiles grow very well at 0 ⁰C while psychrotrophs do not grow very well at 0 ⁰C. Thus, this summarizes the difference between psychrophiles and psychrotrophs.

 Reference:

1.“Microbiology.” Lumen, Available here.
2. “Psychrotrophic Bacteria.” Psychrotrophic Bacteria – an Overview | ScienceDirect Topics, Available here.

Image Courtesy:

1. “Xanthoria elegans 97571 wb1” By Jason Hollinger (original photograph), Papa Lima Whiskey (derivative edit) – This image is Image Number 97571 at Mushroom Observer, a source for mycological images (CC BY-SA 3.0) via Commons Wikimedia
2. “Listeria monocytogenes PHIL 2287 lores” By Elizabeth White – comes from the Centers for Disease Control and Prevention’s Public Health Image Library (PHIL) (Public Domain) via Commons Wikimedia