To make kefir, it takes a team. A team of microbes.
That is the message of new research from EMBL and Patil group and Cambridge University colleagues, published in Nature microbiology today. Members of the group study kefir, one of the world’s oldest and fastest-growing fermented food products seen as a ‘superfood’ with many claimed health benefits, including digestion better and lower blood pressure and blood glucose levels. After examining 15 samples of kefir, the researchers found that it was not surprising that the main species of Lactobacillus bacteria found in kefir grains cannot survive on their own in milk – the main another ingredient in kefir. However, when the sex works together, feeding on each other’s metabolites in kefir culture, they all provide something that each other needs.
“Collaboration allows them to do something they couldn’t do on their own,” says Kiran Patil, group director and co-author of the paper. “It’s particularly interesting how L. kefiranofaciens, which dominates the kefir community, uses kefir grains to bind together all the other microbes it needs to survive – similar to the ruling ring of the Lord of the Rings. One grain for the whole connection. ”
A model for microbial interactions
Kefir consumption was initially popular in eastern Europe, Israel, and regions in and around Russia. It is made up of ‘grains’ that resemble small caraway pieces and are fermented in milk to make a probiotic drink of bacteria and yeast.
“People were storing milk in sheepskin and they noticed that the grains that came out kept the milk from spoiling, so that they could store it longer,” said Sonja Blasche, postdoc in the Patil group and co-author of the paper. “Because milk spoils relatively easily, there was great value in finding a way to store it longer.”
To make kefir, you need kefir grains. These cannot be made artistically, but must come from another batch of kefir. The grains are added to milk for fermentation and growth. About 24 to 48 hours later (or, in the case of this research, 90 hours later), the kefir grains have eaten the nutrients available with them. The grains grow in size and number during this time and kefir process is complete. The grains are removed and added to fresh milk to restart the process.
For scientists, however, kefir provides more than just a healthy drink: it is an easily cultivated microbial community model for studying metabolic interactions. And while kefir is very similar to yogurt in many ways – both fermented milk products or a culture full of ‘probiotics’ – kefir’s microbial community is far larger than yogurt, including not not only bacterial cultures but also yeast.
Learning from kefir
Although scientists know that microorganisms often live in communities and depend on their community members for survival, mechanical knowledge of this phenomenon has been very limited. . Historically, laboratory models have been limited to two or three microphone types, so Kefir – as Kiran explains – offered a ‘Goldilocks zone’ of not too small complexity ( about 40 species), but not too inconvenient for detailed study.
Sonja began this research by collecting kefir samples from several places. Although most specimens have been found in Germany, they appear to have originated elsewhere, as kefir grains have been handed down over the centuries.
“Our first step was to look at how the specimens grow. Kefir microbial communities have many member species with individual growth patterns that respond to their current environment. This means fast and slow growing species and some that vary in speed depending on the amount of nutrients available, “Sonja says. “This is not unique to the kefir community. However, the kefir community had a lot of lead time for coexistence to bring it to perfection, because they’ve been coming together for a long time already.”
Collaboration is the key
Finding out the extent and nature of the interaction between kefir microbes was far from straightforward. To do this, the researchers combined several innovative methods such as metabolomics (studying the chemical processes of metabolites), transcriptomics (studying genome-produced RNA transcripts), and mathematical modeling. This revealed not only major representatives of molecular interactions such as amino acids, but also different sexual dynamics between the grains and the milk component of kefir.
“The kefir grain acts as a basic camp for the kefir community, from which members of the community settle the milk in a complex but organized and cooperative manner,” Kiran says. -this wonder in kefir, and then we will see that it is not limited to kefir. If you look at the whole world of microorganisms, collaboration is also a key part of their structure and function. “
In fact, in another paper from the Kiran group in collaboration with the Bork group EMBL, released today in Ecology Nature and evolution, scientists combined data from thousands of microphone communities around the world – from soil to the human gut – to understand similar collaborative relationships. In this second paper, the researchers used advanced metabolic modeling to show that the constituent groups of bacteria, groups often found together in different habitats, are either highly competitive or highly cooperative. This sheer polarization has not been observed before, and sheds light on evolutionary processes that shape microbial ecosystems. While both competitive and co-operative communities are common, collaborators appear to be more successful in terms of higher abundance and taking over diverse habitats. Stronger together.
###
Disclaimer: AAAS and EurekAlert! they are not responsible for the accuracy of press releases posted to EurekAlert! by sending institutions or for using any information through the EurekAlert system.