  In a few years, space telescopes will investigate our Galaxy to detect
evidence of life, mainly by observing rocky planets. In the last decade, the
observation of exoplanet atmospheres and the theoretical works on biosignature
gasses have experienced a considerable acceleration. The~most attractive
feature of the realm of exoplanets is that 40\% of M dwarfs host super-Earths
with a minimum mass between 1 and 30 Earth masses, orbital periods shorter than
50 days, and radii between those of the Earth and Neptune (1--3.8 R$_\oplus$).
Moreover, the recent finding of cyanobacteria able to use far-red (FR) light
for oxygenic photosynthesis due to the synthesis of chlorophylls $d$ and $f$,
extending in vivo light absorption up to 750\ nm, suggests the possibility of
exotic photosynthesis in planets around M dwarfs. Using innovative laboratory
instrumentation, we exposed different cyanobacteria to an M dwarf star
simulated irradiation, comparing their responses to those under solar and FR
simulated lights.~As expected, in FR light, only the cyanobacteria able to
synthesize chlorophyll $d$ and $f$ could grow. Surprisingly, all strains, both
able or unable to use FR light, grew and photosynthesized under the M dwarf
generated spectrum in a similar way to the solar light and much more
efficiently than under the FR one. Our findings highlight the importance of
simulating both the visible and FR light components of an M dwarf spectrum to
correctly evaluate the photosynthetic performances of oxygenic organisms
exposed under such an exotic light~condition.
