A bit of googling answered my own question: they're just plasitc bags, unlikely to hold pressure for long on the moon. However the faecies itself might provide enough protection in its core for survival. Anything beneath the surface of the turd would be protected against uv, and would have some protection against vacuum and dessication. Maximum surface temperature is usually quoted as 123 deg c, with an average of 107, which is within the survival range for dormant microbe spores. So i wouldn't be surprised if something survived, but it doesn't look like conditions would be protected enough for reproduction, which only puts the moon on a par with mars. Sorry to rain on your parade mate...