Creatures Worth Meeting

[THEO] Okay, picture this. You walk into a workshop, and every tool on the wall only fits one brand of screw. That's molecular biology for most of the history of molecular biology. We built this incredible toolkit — plasmids, promoters, CRISPR — and almost all of it was tuned for about three organisms. E. coli, baker's yeast, maybe a couple of others.

[DR. MARA] The model organisms. We chose them for good reasons. They grow fast, they're safe, they take up DNA readily. But that convenience quietly narrowed what questions we could ask. The vast majority of life on Earth — the microbes doing the interesting chemistry — we couldn't touch genetically.

[THEO] And that's the subject today. Creatures worth meeting. The organisms that aren't on the standard menu, and the slow, grinding effort to make them workable in the lab. Mara, give people the word they'll hear all day — intractable.

[DR. MARA] Intractable just means you can't easily manipulate it. Usually it comes down to two walls. First, you can't get DNA into the cell efficiently. Second, even when you do, the cell destroys it — restriction-modification systems chop up foreign DNA as a defense against phage. That's the arms race I spent my postdoc on, and it's exactly what makes a new organism a nightmare to engineer.

[THEO] And when we say "get DNA in" for a bacterium, the right word is transform — transformation, conjugation, electroporation. Transfection is for eukaryotic cells. People blur those and it drives you a little crazy, right?

[DR. MARA] It's not pedantry. The mechanisms are genuinely different, and calling them the wrong thing signals you don't know which barrier you're fighting.

[THEO] So why bother? Why not stay in the E. coli comfort zone?

[DR. MARA] Because the organism often is the capability. If you want to fix carbon from sunlight, a cyanobacterium already does that. If you want an enzyme stable at ninety degrees, an extremophile already evolved it. You can try to port those traits into E. coli, or you can learn to engineer the thing that already works.

[THEO] Cell factory is the phrase — turning an organism into a little production line for a chemical or fuel or material. And that brings us to the first paper in the arc. Fatma and colleagues, 2020, a review laying out non-model microbes as cell factories.

[DR. MARA] It's a good starting point because it names the thesis the whole field is built on. Non-model microbes can be workhorses, but only if you build organism-specific tools — and CRISPR especially — to get past that intrinsic intractability. Actinobacteria, cyanobacteria, yeasts, fungi. The review's argument is that there's no universal shortcut. You do the custom tooling, species by species.

[THEO] Which sounds exhausting.

[DR. MARA] It is. And that's what makes the second 2020 paper so striking, because it's the field admitting the problem is too big to solve one lab at a time.

[THEO] This is the marine protist one. And I love this just as a piece of scientific organization. Forty-one research groups, a hundred and thirteen authors, funded by the Moore Foundation. They went after thirty-nine species of marine protist.

[DR. MARA] Protists being the eukaryotic microbes that aren't plants, animals, or fungi — a staggering slice of diversity. They deliberately spanned all the eukaryotic supergroups. The whole tree, not one cozy corner.

[THEO] And the scorecard: thirteen first-ever transformation protocols. First dinoflagellate nuclear transformation. First Antarctic diatom. Plus eight more advanced protocols on top.

[DR. MARA] But here's what I think is the real contribution. They published the failures. They distilled everything — what worked, what didn't — into a synthetic roadmap for transforming a new protist. The turning point isn't any single protocol. It's treating tool-building itself as a shared, systematic science instead of a thing each lab suffers through alone.

[THEO] So 2020 sets the thesis and the strategy. Then there's this gap, and the 2024 papers come in attacking from totally different angles. Let's take the cloning one first, because Mara, this is the part where I need the kitchen-table version myself.

[DR. MARA] Modular cloning. The idea is you want to snap DNA parts together like standardized bricks — a promoter, a gene, a terminator — in a defined order, reliably. Golden Gate assembly uses enzymes that cut outside their own recognition site, which lets you design little single-stranded overhangs that act like the nubs on a brick. Matching nubs find each other.

[THEO] So it's LEGO, but the studs are three-letter DNA sequences.

[DR. MARA] Essentially. The de Vries paper from 2024 uses an enzyme called SapI that leaves three-nucleotide overhangs. Three nucleotides is a codon — the unit that codes one amino acid. So you can join parts right at codon boundaries and leave no scar, no leftover junk sequence between them.

[THEO] Which matters because a scar is extra bases that could change how a protein folds or a site functions.

[DR. MARA] Right. And the clever second half is what they call Out-Cloning. Instead of needing a pre-made acceptor plasmid for your specific organism, you generate the organism-specific acceptor on demand from modular parts. For a field where every species needs its own plasmid with its own origin of replication, that's the difference between waiting months and building what you need that week.

[THEO] So it directly answers the 2020 complaint — custom tools, species by species — by making the custom part fast. Where does the CRISPRi Pseudomonas paper fit?

[DR. MARA] That one's Roghair Stroud and colleagues, also 2024, and it pushes the tools out of the flask and into the dirt. P. alloputida KT2440 is a soil bacterium. CRISPRi means CRISPR interference — a dead Cas9, dCas9, that can't cut but still binds, so it parks on a gene and blocks transcription. Repression instead of deletion.

[THEO] And they built it to be controllable — a promoter you can switch on with an inducer — and they stitched dCas9 into the chromosome using mini-Tn7, which is a transposon tool that drops your cargo at a specific site.

[DR. MARA] And the headline is they achieved gene repression in situ in the rhizosphere — the zone around plant roots — a living, messy environment. They also shut down pyoverdine, a siderophore. Siderophores are molecules bacteria secrete to scavenge iron; whoever grabs the iron wins the competition. So they're not just editing a gene, they're tuning who outcompetes whom in a microbial community.

[THEO] That's a big jump. From "can we get DNA in at all" in 2020 to "can we control gene expression in soil and referee a competition between microbes."

[DR. MARA] And the last two papers remind us why we want these organisms in the first place. The polyextremophile framework boils extreme-environment stress down to four root causes — reactive oxygen species, covalent damage, protein unfolding, membrane fluidity — and asks which combinations of extremes reinforce each other versus cancel out. That turns designing an extremophile chassis from guesswork into prediction.

[THEO] For space, even. In-situ resource utilization — making stuff on Mars instead of shipping it.

[DR. MARA] And then Deming's piece on Colwellia, the psychrophiles in sea ice that keep functioning below the temperatures we predicted should stop them. A reminder that the organisms are still ahead of our theories.

[THEO] Which is the through-line, isn't it? Ten years ago the question was "can we touch this thing at all." Now it's "can we predict and control it in its own habitat." The creatures were always worth meeting — we just finally built the tools to say hello.

[DR. MARA] And the roadmap's published. So the next lab doesn't start from zero.

[THEO] On that note — we'll pick up the extremophile chassis thread after the break. Stay with us.