Posts Tagged ‘bacteria’

Sourdoughs of Space

lacto-bigI recently read Ferrett Steinmetz‘s short story “Sourdough Station” that as the title suggests involves a sauerkraut-making operation on a space station. That’s not all the story is about, of course, but it did get me thinking about food and fermentation and what that might mean to folks living in space.

Sauerkraut is fermented cabbage and is high in vitamins, fiber, iron, folate and other nutrients.  Combine that with sauerkraut’s relatively long shelf life, and it seems like an ideal food for isolated outposts in space. Astronauts have already been experimenting with growing nappa cabbage and vegetables on the International Space Station, so it looks likely that growing leafy greens in space is within the realm of possibility. Assuming that the fermentation process works as well in space as it does on Earth, sauerkraut could become a space habitat staple as humans spread out among the stars. Or perhaps spacegoers would prefer something more like spicy Korean kimchi, since microgravity can dull the sense of taste.

Lactic acid bacteria  – primarily species of Lactobacillus – are not only involved in the process of fermenting sauerkraut and kimchi, but also the production of yogurt and cheese from milk, and making sourdough bread sour. But not any old microbe will do for optimal fermentation. Different species of bacteria are used in the production of different foods: Lactobacillus kimchii is a unique species found (naturally) in kimchi, Lactobacillus helveticus is used to ferment milk into swiss cheese, Lactobacillus delbrueckii subsp. bulgaricus (discovered in the course of researching the longevity of Bulgarians) and Lactobacillus acidophilus are used in yogurt production, and Lactobacillus sanfranciscensis gives sourdough bread its sourness.

The different species and strains of bacteria vary in their biochemistry and so can significantly affect the flavor of the sauerkraut or yogurt or bread being produced. Often there are several different species of bacteria that are involved in the fermentation process. DNA analysis during the sauerkraut production process has found a number of different bacterial species present during the fermentation process. There may be an entire ecosystem of microbes in every fermentation pot.

So why is this important to my hypothetical sauerkraut-eating spacefarers of the future?

Even assuming there are no technical issues with designing safe fermentation vessels or growing vegetables to ferment, culturing the necessary microbes might turn out to be a challenge.

8344600413_0dd3a38dba_mEven under optimal conditions of temperature and humidity, space stations are unlikely to have gravity equal to that on Earth and that can affect bacterial growth. For example,  Lactobacillus acidophilus has been shown to grow more quickly in the microgravity environment of the International Space Station.

It’s not a stretch to wonder whether new strains of bacteria will have to be developed – or perhaps will arise naturally – for the production of deliciously fermented food in space. It wouldn’t be that far different from the development of new strains of yeast that revolutionized the brewing industry here on Earth.

But the fact that the background radiation levels on a space station or spaceship could be significantly higher than that on Earth could significantly raise the mutation rate in bacteria onboard, and there is always a risk that such mutations could render otherwise harmless bacteria dangerous. And even harmless bacteria could harbor mutations that modify their metabolism in such a way that it affects the fermentation process or the flavor of the fermented product.

At the turn of the 20th century Alaskan gold rush old-timers were known as Sourdoughs because they were reputed to protect their sourdough cultures during Arctic winters by keeping lumps of dough warm with their bodies. Spacefarers would similarly have to carefully protect and maintain any bacterial cultures used in food production.

I can imagine humans spread through our solar system and beyond, with different space colonies developing their own special fermentation cultures. Freeze-dried microbes would be easy to carry and trade, perhaps helping form the basis of a space culture barter system. They could be known for this, perhaps becoming the Sourdoughs of space*. They probably wouldn’t be so grizzled (or as nearly exclusively male) as the Yukon prospectors of a century ago, but like the original Sourdoughs would be living in an environment hostile to humans and they would known for the products of those precious microbes they maintained.

Since food plays such an important role in human culture, I like to think that’s how we’ll refer to ourselves.

Or maybe I’m just hungry …

Top image: Fermented foods made with lactic acid producing bacteria. From “Genomic comparison of lactic acid  bacterial published“, DOE Joint Genome Institute.

Bottom image: Lactobacillus casei uploaded by AJ Cann (AJC1) on Flickr and shared under a CC BY-SA 2.0 license.

Yogurt makes you … shinier

At least if you’re a mouse. Research published this month found that mice fed yogurt were slimmer, sleeker and shinier than those that didn’t.

The male yogurt-eating mice also had larger testicles. (The junk-food eating mice had smaller testicles.) Female mice weren’t left out: they were smooth and shiny too, and had larger healthier litters.

In other words, eating yogurt made mice more attractive and more fertile, and presumably healthier. The researchers don’t know why, but they suspect it might have to do with the live bacterial cultures in the yogurt.

By the numbers, the human body is mostly bacteria: about one trillion human cells, and about ten trillion bacteria. (I don’t know the numbers for mice, but they’re probably similar.) We don’t even know what most of them are, though scientists think there are around 500 different species.

Many of those bacteria live in the digestive system, having colonized the infant during birth or shortly after. They help to digest the things we eat, release vitamins, help to keep out disease-causing bacteria: all sorts of useful things. The humans studied so far fall into one of three enterotypes, each of which has similar distinctive gut assemblages (even though they eat similar diets).

Nobody knows exactly what that means yet, but one possibility is that different enterotypes are more efficient at digesting particular foods. They may also be more or less effective at providing vitamins to their host. The abundances of different species change in response to diet, but mostly within certain limits. Gut flora have been linked to obesity, suggesting that bacteria may affect metabolism or efficiency of digestion. Having (or eating) the right bacteria might also be related to longevity.

When gut bacterial assemblages decline or get unbalanced, often as a result of taking antibiotics to treat some other condition, all sorts of problems can occur. One particularly nasty invader is Clostridium difficile, a bacterium that can cause persistent diarrhea and may become debilitating or life-threatening. Even C. diff, as it’s not-so-fondly known, is vulnerable to a diverse and balanced set of gut bacterial: a fecal transplant from a healthy individual is an effective cure.

Gut bacteria could have global environmental implications too: scientists are looking for ways to modify ruminal bacteria in cattle so that they eliminate less methane, a powerful greenhouse gas.

This stuff has all kinds of science-fictional implications. What about modifying the gut flora of planetary colonists to help them digest new foods, or to produce vitamins that they no longer get from their diet? Or superfoods that promote health or shininess or fertility? Such superfoods could be proprietary, or addictive. What happens if people try to culture them at home? Making your own yogurt is easy, and using a commercial yogurt as the starter ensures that you have the same culture. For the probiotics to contribute to the gut flora, they have to be alive.