Description of Micro-Organisms like Bacteria, Virus, Fungi etc is given in hindu mythology epic poem, Mahabharata which was written more than 5000 years ago.
Scientists have found existence of Bacteria in 17th century AD but they were known as minute organisms, invisible to naked eye, but destroyed at blink of an eyelid.
Arjuna, the third among Pandavas talks about ‘Survival of the Fittest‘, which was later advocated by Charles Robert Darwin.
Santi Parva Section XV
Arjuna talks about the strongest species killing the weakest for its survival and how that is the nature of this world.
“I do not behold the creature in this world that supports life without doing any act of injury to others. Animals live upon animals, the stronger upon the weaker. The mongoose devours mice; the cat devours the mongoose; the dog devours the cat; the dog is again devoured by the spotted leopard. Behold all things again are devoured by the Destroyer when he comes.This mobile and immobile universe is food for living creatures. This has been ordained by the gods. The very ascetics cannot support their lives without killing creatures. In water, on earth, and fruits, there are innumerable creatures. It is not true that one does not slaughter them. What higher duty is there than supporting one’s life? ”
He even talks about how gods are given powers to destroy, punish people in this world and ahimsa (non-violence) is not for everyone (especially kings/kshatriyas/rulers).
सूक्ष्मयॊनीनि भूतानि तर्क गम्यानि कानि चित
पक्ष्मणॊ ऽपि निपातेन येषां सयात सकन्धपर्ययः
Transaltion : There are many creatures that are so minute that their existence can only be inferred. With the falling of the the eyelids alone, they are destroyed.