Yeah the paper seems more like a material science paper than a biology paper. There was no test/simulations/discussion about biological function; similar to DNA computing/data storage, it’s mostly interested in the properties of the material than how it interfaces with pre-existing biology.
They did optimize for foldability, and did successfully produce the folded protein in (standard bacterial) cells. So it can be produced by biological systems (at least briefly), and more complex proteins had lower yields.
Their application they looked at was hydrogels, and it seems to have improved performance there? But functioning in biological systems introduces more constraints.
I would strongly recommend reading Species Concepts in Biology for a history and explanation of the current system(s). In summary, there are multiple joints at which you can carve reality, and which joints you choose to carve depends on why you are carving reality in the first place.
As someone who studies viruses of bacteria, how are you supposed to apply the Biological Species Concept to asexual organisms anyways? Are there no bacterial “species”? But we need a way to categorize and talk about them, even if they’re not a species under the BSC. Even if this will group bacteria together whose genome lengths can vary by an entire order of magnitude.
Fundamentally, the Species Concept is the same problem. We need a way to categorize and talk about animals, so we find ways to categorize them based on how useful the categories are. Birds are feathered reptiles. Reptiles are non-feathered reptiles. We form these categories not because they carve reality at the phylogenetic joints but because these categories are useful. Fish are fish. Trees are trees.
(Viral species are even worse. Linear phylogenetic inheritance is thrown out the window. Everything is modular and recombines with each other.)
I don’t really follow the IUCN or like the focus on “biodiversity” for its own sake (just expose them to mutagens if you want more genetic diversity) (I also have philosophical issues with “conservation”—what, exactly, are you conserving and why is that time more worth conserving than any other time?) I’m probably informed by my study: in my opinion everything is a bag of genes, and genes constantly flow between them; species aren’t real and are just useful lines to draw in a continuum of gene flow, which constantly changes over time.
But can you verify it? Do you have experimental evidence that a human from location A can form fertile offspring with a human from remote location B? That’s why geographical isolation is used to define species; because they (mostly) don’t overlap, we don’t have evidence if they can or cannot interbreed. Only when we have evidence of hybridization can we start discussing whether to collapse them into the same species (ring species notwithstanding).
Also, I don’t know nearly enough about plant hybridization, but I’m pretty sure that plants can hybridize extremely easily and if we applied only an “interbreeding” species concept the categories would collapse into uselessness.