How microbes survive in extreme environments
Feb 2023
It’s getting hot in here…
It is estimated that there are 10⁹ times more microbes on Earth than there are stars in the universe. 90% of the cells in the human body are microbes that live everywhere in and on you, from your gut to your skin. Microbes are by far the most diverse life form, living in extreme environments from 400ºC deep sea hydrothermal vents to highly acidic sulfuric pools. Studying their structures and mechanisms has applications for weather control, biofuel generation, energy and so much more.
Us fragile humans prefer temperatures lower than 50ºC. But for certain bacteria, called thermophiles, the optimal temperature range can go way beyond 100ºC. These bacteria have certain built-in mechanisms for making sure that they don’t just melt. The hotter it is, the more likely it is for proteins to unfold, since heat causes molecules to bounce around faster, disrupting the bonds holding the protein in its structure.
To avoid denaturing, proteins have densely packed, hydrophobic (water-repelling) interiors and more ionic bonds on their surface, the strongest kinds of intermolecular forces. Thermophiles also have more chaperone molecules that contribute to protein folding and cell membranes with more saturated fatty acids, which are rigid and provide stability.
Enzymes from these microorganisms are used in many industrial applications, such as food, paper, detergents, and textiles.
But winter is coming…
On the other end of the spectrum, we have psychrophiles, that survive in extremely cold temperatures. In contrast to their hot-headed relatives, psychrophiles need to find ways to avoid overly slow enzymatic activity. Therefore, they have shorter, more unsaturated fatty acids, more hydrophilic (water-loving) molecules and less ionic bonds, providing flexibility and fluidity.
Imagine, for example, how butter stays solid in the fridge but melts at room temperature: psychrophiles want to avoid being too solid, because then they can’t carry out functions necessary for life, such as movement and reproduction.
These bacteria have also served as inspiration in industries such as cosmetics, refrigeration and pharmaceuticals.
Other extremophiles
Acidophiles thrive in pH levels of 2.0 and below. For context, pH ranges from 0 to 14, and the average pH in the human body is 7.40, right around the neutral range. These microbes are found in acid mine drainage, volcanic soils, and our stomachs. They have a highly impermeable membrane for protection, specialized proton gradient mitigation and resistance towards metals, making them applicable to electricity generation, animal feed digestibility and detoxification of harmful metals.
Barophiles survive in extreme pressure environments, such as ocean floors. Halophiles regulate their osmotic balance to exist in high salt concentrations. There are also bacteria that range from complete dependance on oxygen for survival (obligate aerobes), to bacteria that can tolerate oxygen but don’t need it (aerotolerant anaerobe), to bacteria that thrive in anoxic (no oxygen) environments. There are even microorganisms that are resistant to bacteria.
Understanding how these incredibly diverse microbes function can open up opportunities for innovation in a wide range of industries and shine light on the conditions that make life possible.