Uh ... I've seen one or two threads which have lots of vigorous debate over whether any life is natural. The assertion is that it's a design of some kind.
I'm still trying to get my mind around how you can have a meaningful abstract definition that can't be applied in the abstract.
What does "artificial" mean in the absence of an object's history?
The term "natural systems" means systems which occur in nature. It doesn't speak to design one way or the other.
js1138's question is like a challenge.
If the structure is the same, the difference between natural and artificial can be discerned from origin if that can be determined by the observer. I'm thinking of sci-fi human-looking artificial lifeforms, laboratory "life" in a test tube, etc.
For instance: Did it originate involuntarily (nature) or voluntarily? And if voluntarily, by replication (nature) or by creation? And if by creation, by intelligence of another lifeform (artificial) or by God (nature)?