Grand Prismatic Spring 

If you have visited the Grand Prismatic Spring in Yellowstone national park, or any other thermal pool for that matter, you surely remember the impressive colorful rings around their edges. Although the Grand Prismatic gets its name from the resemblance of these colorful rings to the splitting of white light through a prism into a rainbow, the colors in these rings are unrelated to refraction of light. Commonly called microbial mats, they are actually living bacteria, and their color arises from pigments secreted by the bacteria.

Why do the Grand Prismatic Spring rings differ in color?

Bacteria were one of the earliest living creatures during evolution. They survived all these years with their adaptable nature to extreme conditions. So, while the bacteria in our gut love a comfortable body temperature of 37 °C, some others, like thermophiles, prefer much higher temperatures. Thermal pools are literally ‘hotspots’ for such thermophiles. The pools consist of a temperature gradient; they are extremely hot in the center (where almost no lifeforms survive) and cooler towards the edges. Different types of bacteria thrive in these different rings, sorted according to their temperature preference. For e.g., the orange filamentous cyanobacteria prefer a cooler outer rim temperature of 45-60 °C, while Thermus aquaticus, which produce a yellow pigment thrive in the inner rim at 70 °C. 

Why do bacteria produce pigments?

Apart from unintended tourist attention, bacteria actually produce pigments for numerous self-benefits: photosynthesis, protection from UV radiation, and stress-combat. Some pigments also possess antibiotic properties, while some confer resistance to antibiotics, causing the menace of multi-drug resistant microbes. Microbiologists have managed to isolate and use bacterial pigments as natural dyes in textile, pharma, and food industries. The thermophile, Thermus aquaticus is an undying hero in biotech industries. Any DNA analysis involves its amplification using a method known as polymerase chain reaction (PCR), as the amount of DNA from the original samples is quite low for further experiments. Thermus aquaticus bacteria are the source of the greatest boon in biology research: Taq polymerase, an enzyme that is functional at high temperatures and widely used in DNA amplification by PCR. 

Further reading

1. Brock, Thomas D. Life at high temperatures. Yellowstone Association for Natural Science, History &, 1994.
2. Venil, Chidambaram Kulandaisamy, Zainul Akmar Zakaria, and Wan Azlina Ahmad. “Bacterial pigments and their applications.” Process Biochemistry48.7 (2013): 1065-1079.
3. Breithaupt, Holger. “The hunt for living gold.” EMBO reports 2.11 (2001): 968-971.