Attached Microbes

The Attached Microbes (密着微生物), also known as the Martian Microbes (火星微生物), are supposedly a lifeform native to the planet Mars in the Toaru Majutsu no Index universe, an intelligent species speaking Japanese. They are actually artificial microbes, developed in the scientific project called Mars World experiment.

Toaru Majutsu no Index: Mars SS
After receiving signals from the Martian Microbes in her laboratory, Bisai Otome wished to take them back to Earth and shelter them. She tried to artificially create similar microbes by reproducing the same environment as Mars on Earth and thus make regular microbes evolve. This was so she could investigate the microbes beforehand. This experiment was conducted in a small dome named Mars World (マーズワールド). She managed to create microbes fertile enough to survive in the Martian environment, yet they gained no calculation ability like that of the Martian ones.

Bisai Otome raised the suspicion that someone might be pretending to be the Martian Microbes based on how the information about them leaked out; this is left unanswered.

Baggage City Arc
Shar Berylan mentioned Natural Selector participant who claims to talk with a mass of bacteria collected from Mars. It is unknown if the 'mass of bacteria collected from Mars' is related to the Martian Microbes.