Does UV light treatment of water to kill pathogenic microbes also kill the novel life forms?

Unfortunately, this is correct. It is a function of time and that is true for the antimicrobial activity to begin with. It will be a fine line between the two. In other words, the amount of UV exposure needed for sterilization with respect to microbial organisms known to science, the others of a novel form may survive, although barely, but it is such a fine line that it will be impractical for people to achieve reliable and total sterility with regard to potentially harmful microbiological life and these novel life forms being allowed to persist unharmed. So this is not a practical strategy if one’s goal is to maintain the novel life forms in the presence of significant bacterial pathogens, a filtration strategy would be a better course to use.