Path 10: Bioengineering Novel Life Forms – “Build to Understand” Approach

Rationale: One powerful way to test alternative biochemistries is to create them in the lab. This path doesn’t correspond to a single chemistry, but rather a methodology: using synthetic biology and bioengineering to construct organisms (or protocells) with alternative chemistry, thereby probing viability directly. If we can build a cell that uses XNA instead of DNA, or that has a mirror genome, or that replaces a key element (like an E. coli that lives without phosphate), we obtain proof that life can function that way – or discover fundamental barriers. This path complements the observational paths by providing tangible “alien” life models on Earth. For example, Venter’s team built minimal genomes; the next step could be incorporating non-standard amino acids or XNA into those genomes systematically. Similarly, Jack Szostak’s group works on RNA-based protocells – one could attempt an ammonia-based protocell in the lab to see what hurdles appear. The rationale is that by pushing engineering beyond Earth-normal biology, we identify which aspects of biochemistry are universal requirements and which are just one solution among many. It’s an unsolved challenge how far we can deviate and still have a living system. Also, this approach helps develop biosafety measures (e.g., an orthogonal biochemistry could be used for genetic confinement – an organism that can’t mix with natural life, as discussed for mirror or XNA life). In summary, “build to understand” is a path that ties together insights from all other paths into practical demonstrations.

Prerequisites: This ambitious path requires advanced tools of synthetic genomics, chemical synthesis, and possibly automated evolution platforms. A major prerequisite is the ability to chemically synthesize whole genomes or chromosome-sized XNAs, since natural enzymes may not copy them. We also need robust cell-free systems: for instance, to test a new biochemistry, one might start with a cell extract and add synthetic components to see if it can sustain metabolism or replication. Another prerequisite is computational modeling to predict viability – because constructing a full alternative cell is extremely complex, we’d use models to narrow down designs (like what minimal set of changes could yield a working mirror-E. coli). Having a library of modular biological parts is needed – e.g., ribosomes that accept unnatural amino acids (some progress here: the genetic code has been expanded artificially to include 1–2 extra amino acids beyond the standard 20), or polymerases that work on XNA (from Path 6). Essentially, Path 10 stands on the shoulders of Paths 5–7: it needs the outcomes of those (like a polymerase from Path 6, a mirror enzyme from Path 7, a P-free membrane from Path 5) to assemble into a whole system. Lab infrastructure prerequisites include containment facilities (in case our novel organism could interact unexpectedly with the environment – though using XNAs or mirror forms inherently reduces that risk as those forms are inedible and non-infectious to standard life). Also, extremely sensitive analytical methods are needed to troubleshoot these synthetic cells – e.g., if your engineered cell isn’t thriving, you need to analyze which pathway failed (metabolomics for unusual metabolites, microscopy for structural issues, etc.).

Dependencies: All previous paths feed into this engineering effort. For instance, Path 6 gives the building blocks for an XNA genome, Path 7 provides knowledge for synthesizing mirror proteins, Path 5 gives ideas for alternative metabolism. Path 10 then attempts to integrate some of these into a single prototype. There’s dependency on systems biology: to redesign life, we must know how to tweak multiple pathways without fatal consequences. A minimal cell like Mycoplasma (with ~500 genes) might be the chassis to re-engineer with alternative components one by one (dependency on minimal genome research). Another dependency is on automation and directed evolution: some things we can’t rationally design, but we can evolve in the lab if we set up selection pressure. For example, to make a DNA-free organism, one idea is to progressively replace DNA bases with analogs until the genome is entirely synthetic (done partially by Romesberg’s group for an expanded-code E. coli). This requires continuous culture and selection – thus depending on evolutionary methods. Importantly, Path 10 depends on a strong ethical and safety framework: creating novel life is subject to bioethics and regulation. This is not a scientific dependency per se, but without addressing it, the research could be stymied. Garnering support for such visionary experiments means aligning them with societal values (e.g., highlighting biosafety and knowledge gains).

Signs of Progress: Some are already visible: e.g., semi-synthetic organisms with 6-letter DNA (two extra bases) have been made to stably propagate the expanded alphabet. That’s progress toward a broader genetic system. Another sign: the genetic code expansion – scientists have engineered cells to use a 21st or 22nd amino acid by reassigning codons. This shows we can push the biochemistry envelope within living cells. In 2019, researchers recoded the entire E. coli genome to remove a particular codon, freeing it to be repurposed – an example of large-scale genome editing paving the way for further changes (like incorporating noncanonical chemistry). On the mirror life front, while no mirror cell exists, signs of progress include mirror enzymes retaining activity (which indicates viability in principle) and the fact that no fundamental physics disallows mirror life (it’s just a matter of implementation). A big future milestone would be a phosphorus-independent bacterium in the lab. Perhaps by knocking out pathways stepwise and providing alternatives, one could coax a microbe to use arsenate or purely sulfur/energy currencies. Even partial success (say a strain that uses 30% less phosphorus than wild type by substituting some components) is a sign. Another sign is creating a cell-like system from scratch (bottom-up synthetic biology) that operates with XNAs or other deviations. The construction of fatty-acid vesicles that can grow and divide (by Szostak’s group) was a sign we can mimic cellular compartments; replacing their RNA with XNA would be another. Each demonstration – an alternative polymer sustaining information, an alternative catalyst running metabolism, an alternative membrane enclosing it – is a milestone. When one of these artificial assemblies actually achieves self-reproduction and evolution, even if only in a simplified form (e.g., a protocell that makes daughters with slight variations), we will have essentially created a novel life form. That will conclusively show which biochemical features are non-negotiable and which can be different. In essence, success in Path 10 would be the Rosetta Stone of biochemistry: building a second example of life to compare with Earth life. Even intermediate “half-lives” (like a microbe with a hybrid DNA/XNA genome or a cross-chiral ribosome) are major progress indicators, showing us the continuum of possibilities between known life and truly alien life.

(Path 10 is a meta-path combining approaches from all other paths — it serves as the engineering integration layer. Base camps for this path would recap cross-steps from Paths 1–9, so they are not detailed separately here. The document notes: “Path 10 base-camps might include specifics like ‘Design of mirror-XNA orthogonal cell’ or ‘Incorporating XNA into living cells’ – but Path 10 is meta, combining multiple as said, so its base-camps might just recap cross-steps from others and is somewhat redundant.”)