  The discovery of potentially habitable planets around the ultracool dwarf
star Trappist-1 naturally poses the question: could Trappist-1 planets be home
to life? These planets orbit very close to the host star and are most
susceptible to the UV radiation emitted by the intense and frequent flares of
Trappist-1. Here we calculate the UV spectra (100 - 450 nm) of a superflare
observed on Trappist-1 with the K2 mission. We couple radiative transfer models
to this spectra to estimate the UV surface flux on planets in the habitable
zone of Trappist-1 (planets $e$, $f$, and $g$), assuming atmospheric scenarios
based on a pre-biotic and an oxygenic atmosphere. We quantify the impact of the
UV radiation on living organisms on the surface and on a hypothetical planet
ocean. Finally, we find that for non-oxygenic planets, UV resistant lifeforms
would survive on the surface of planets f and g. Nevertheless, more fragile
organisms (i.e. \textit{E. coli}) could be protected from the hazardous UV
effects at ocean depths greater than 8m. If the planets have an ozone layer,
any lifeforms studied here would survive in the HZ planets.
