Don't forget about Deinococcus Radiodurans. It's extremely
radiation-tolerant, though I don't know quantitatively how long it

could

stand the typical radiation flux in interstellar space. One account I
found stated that its ability to live and reproduce was unaffected by

a

1.5 million rad dose of ionizing radition. That's a couple of

thousand of

times what it takes to kill a human.

I wonder how old this organism is, could be interesting looking for
anything turning up in the DNA such as a pattern etc, if it is so
resistant to radiation it may well be that it has suffered the minimum
of damage through time.
It would be good if something like that would be fundable, as SETI is
(or was) to find distant transmissions, this could be far cheaper and
no less unlikely/likely than a message being beamed across the void.
Maybe there are several means, in case we don't see the transmission,
we may discover the message in the DNA, maybe there is another or there
are more backup plans in case we don't get the hint!