Jo: What is your relationship with microbes?

David: There isn’t a human being on Earth that isn’t in a deeply enmeshed and utterly intractable relationship with microbes. We are absolutely dependent on them. We are evolved from them. They are the ground floor for life.

If you look at the diversity of bacteria or of yeast - or protozoa, or amoebas - it dwarfs the diversity of the animal and plant world. Anything that we can see with our eyes is a fraction of the complexity of microbial evolution. They live on and in me. I’m dependent on them for normal digestion. My gastrointestinal tract, the health of my skin, all of it is dependent on microbes that use me as an environment. Organisms are more than just environments to each other. Organisms are entire worlds.

Everything from the pets in your house to a tree in a forest, they’re all dependent on microbes to function. And there’s this endless interchange of metabolic and bioinformational communication that mediates our world.

To engage with a microbe beyond, say, catching a cold or getting an ear infection, to actually understand what they need and how they work and their rhythms and their cycles - I see fermentation as an extraordinarily powerful tool to be able to foster relationships with microbes in which you understand their needs and their wants.

I don’t mean to anthropomorphise these creatures that are really, in so many ways, at once the most complex things imaginable but at the same time the simplest forms of life. But ultimately, what you do when you interface with microbes through fermentation, by working with them, by coaxing out the products of their metabolisms, you’re really interfacing with the rhythms of life itself.

Fermentation has definitely changed how I live in and view the world. The funny thing is going through it with them, learning about microbes so intimately, is a kind of ratchet. There’s no going back. Once you’ve seen the world from their perspective, you can’t unsee it, and everything forever onwards is filtered through a microbial view of life.

Jo: How are we so detached from this world of microbes?

David: We’ve always treated these things as some sort of a mythic force. Whether that was Dionysus or Bacchus or any of the gods of the harvest or the gods of wine, be it palm wine in west Africa or fermented cacao in Mesoamerica, we attributed these things to [divine forces], things that we thought lay beyond our perception, not because they were so small that they were invisible, but because they felt so big that they couldn’t possibly be of this world.

I think it’s completely normal to be disconnected. We live in a medium sized world, so we pay attention to medium size things. Bacterial communication relies on versatile chemical signaling molecules called autoinducers, which regulate bacterial gene expression in a process known as quorum sensing. Individual bacteria can sense and react to other bacteria next to them through autoinducers and quorum sensing, but they are also completely unaware of the person that they live inside.

It goes both ways. The universe echoes through scales of size and time. I wouldn’t say that it’s our fault that we’ve been blind to the finer details of microbial domains for most our species history. We’re made of the world and ultimately we have to interact with it to be able to edge towards some version of the truth about its constitution. That’s why the science of microbiology has been so informative. Lots of things that we’ve known in our hearts as folk science [have been shown to be true].

We’ve only recently realised the implications of that branch of science. Now that we have, the art of fermentation takes on a whole new meaning, because it’s not just the mastery of craft. It is about having the tools and new types of knowledge to interface with such very different forms of life. Fermentation allows you to build a bridge into their world, to hold a medium sized thing in your hand, that might be 25cm across. Something you can pick up, smell, and inspect, that allows you to cross over into their world, a world that you wouldn’t have had access to, at least as an idea, two or three hundred years ago.

Jo: What can we learn from microbes and the fermentation process?

David: When a batch of kombucha fails and the symbiotic culture of bacteria and yeast (known as the mother) goes limp, and you transfer it to a new container, brew a new base and watch it spring back to life, what you’re seeing as resilience is a population level effect. It’s uncountable organisms. It’s trillions of cells of bacteria and yeast in that five-litre bell jar. And maybe 99.99% of them died because they didn’t have the nutrients needed to sustain their own metabolisms and keep dividing.

But that microbial resilience is just evolution. And evolution, though we may think it poetic, is mercilessly unfeeling. It’s predicated on death and extinction. And that’s exactly the lesson that we should take away. That the cost of failed symbiosis is sometimes near eradication. There’s a lot to be said for actively paying attention to those implications and understanding that resilience can also imply untold amounts of suffering.

What can we learn from microbes? We can learn how to work together and not get blindsided by a changing environment, but actively adapt to it before disaster strikes. Because the sort of human resilience that I think we would prefer would see us all continue, versus the sort of microbial resilience that sees only a lucky few squeak by.

Jo: How do you think we can engage the general public with the importance of microbes?

David: You know what would be a really fun exercise? A video that showed a side-by-side split of two people going through a completely western day, but one with fermentation and the other missing everything that wasn’t available to them.

Do you imagine what a McDonald’s cheeseburger would taste like without fermentation? It would be so funny to see a plain white flour flatbread and no mustard, or cheese. On a cheeseburger. No pickles. Just raw cucumbers. What would that look like?

It would be absurd and it would probably taste horrible. But the point is that I think that reaching people where they are and through their existing habits is a great way to communicate and enlighten and educate people about the importance of fermentation.

I think the kneejerk reaction when people hear “fermentation” back in the late nineties before it blew back up into everyone’s public consciousness, is that it was something gross or stinky or implied rotting fish or whatever.

But some of the most expensive comestible beverages and the finest cheeses on Earth are fermented. So there are genres of fermentation that exist as cultural edifices to the most fine and desirable objects made by humankind.

Not that we make them ourselves. They’re made by microbes and plants and humans. It needs all three. But I really do think that meeting people where they are and explaining what already exists within the world of fermentation, to lift up the veil of what goes on inside all these stainless-steel factories that sell something without telling you how it’s made, you know, I think that helps a lot.

I think that we have to stay vigilant about communication and accessible information about these things so it doesn’t just become a niche interest. It deserves to be blown wide open and deserves to be a part of everyone’s understanding of what it means to be human. I think learning about fermentation in high school, for example, is way more important than learning about rocks buried in the centre of the Earth. Knowledge of fermentation is something people can actually use in life.

Jo: Where do you think current thinking about fermentation will lead us in ten years time?

David: It’s so easy to ferment, that’s the thing. There may be this experience gap if someone hasn’t held your hand or told you that it’s OK that something looks this way or that there’s a little bit of mould on top of the sauerkraut. I think once you get past that, it becomes so easy and it’s so rewarding to have the stuff in your fridge or fermenting on your counter. I would hope we get back to the point of parents just doing this with their kids, so we can hook people young and get the next generation. This is Coca Cola and McDonalds’s marketing trick, if you market to eight-year-olds you hook them for life.

There’s no one lobbying to market to eight-year-olds the joy of pulling up your own carrot from the ground or shredding that carrot and some kohlrabi and some cabbage into an amazing kraut that you can have on your hotdog or with your fishcakes. So that really rests on anyone who’s interested in this stuff today to implant in the next generation. Again, it’s a bridge to understanding nature in a much more intimate way.

Sometimes as a fermentation hobbyist, teaching just one class of students at an art university or a community centre how to ferment can feel good in the moment, but when you take yourself out of it, you’re like: “What does this really mean in the face of some of the biggest food corporations on Earth?” But if the history of microbial life has any teaching to do in that regard, big things have small beginnings.

Jo: How can microbes make food delicious? How do you think flavours have changed your perception with food as a chef?

David: I think you can achieve some extremely satisfying flavours. They are flavours that definitely grow on you. I dare say that they can edge towards being a bit samey if you are heavy-handed with it, but it is also extremely easy to be adept at changing the overall hue of a painting. Sometimes just a drop of a garum or Thai fish sauce in the most unassuming places, just one drop can flutter beneath the surface to elevate a dish fivefold.

Mixing tomatoes and fruit, one of these classic flavour combinations that’s sees something savoury mingle with something sweet: flavours of fermentation are great bridges between disparate main components.

There’s a lot of reasons why humans might have settled on the foods that we’re very familiar with: anything that you find in a grocery store, the 100 or so plants that most of the people in the western world eat throughout their lives. Once people start eating a specific variety of carrot, they keep eating it.

And just by the sheer virtue of their being eaten you end up in this reinforcing feedback loop. But just across the valley, a short walk away, is something that people didn’t figure out that still grows wild.

I ferment for myself at home. I just pulled off a batch of sauerkraut. I bought everything to make a radish kimchi tomorrow, just to have stuff in the fridge. I love these flavours - I love having them around. I’m always kind of playing. You’ll find all sorts of counterfactual histories that are accessible if you know what to look for and curious enough to explore. I remember when I did lacto-fermented unripe figs and how wild those tasted. Or the time I made a kombucha out of roasted seaweed. Or the first time I ever fermented oyster mushrooms. The process of katsuobushi can be applied to everything, from pumpkin to horseradish. It’s such an amazing, endless world of discovery.