Which one of the following living organisms gives litmus ?

Litmus is a natural water-soluble dye mixture used as a pH indicator to determine the acidity or alkalinity of a substance. It is primarily extracted from various species of lichens, which are symbiotic organisms composed of fungi and algae. Specifically, the genus Roccella, including species such as Roccella tinctoria and Roccella montagnei, serves as a major source for producing litmus and the dye archil [1]. While other organisms like Saccharomyces (yeast) are microorganisms used in fermentation and bread-making [1], and protozoa have been studied using litmus to observe pH changes in digestion vacuoles, they do not produce the substance themselves. Lichens are unique in their biochemistry, producing specific chemical compounds that are not found elsewhere in the natural world, making them the definitive biological source for litmus.

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 2: The Invisible Living World: Beyond Our Naked Eye > Activity 2.8: Let us perform > p. 21