“New bacteria/plant cell symbiosis discovered”

And if “symbiosis” is too much, “combination”. I also like “meld(ing)”, but that might be somewhere in the middle.

I wouldn’t use “hybrid” because that word has definitely made it into common vernacular and implies they’ve bred which isn’t strictly accurate, and “chimera”, while more accurate, is probably the more terrifying-sounding, if not still technical alternative.