Lactic acid bacteria play a fundamental role in the food-intestinal microbiome axis. Food is the primary source of lactic acid bacteria for the intestine, a study of their genomes shows in Nature Communications.
The intestinal microbiome is a complex set of microorganisms that works in our intestines and plays a fundamental role in our health.
The functioning of the gut microbiome can be helped by probiotic microorganisms, many of which are lactic acid bacteria.
In addition to being available as supplements, probiotic lactic acid bacteria can also be taken with certain food categories.
How many and which of these bacteria then become part of the intestinal microbiome potentially influencing human health? This is the question answered by the newly published study.
The fingerprint of a microorganism is its DNA, its genome. Analyzing hundreds of thousands of lactic acid bacteria genomes present in food and in human intestinal samples from all over the world, the researchers found that lactic acid bacteria are so similar to those present in the human intestine, that it is legitimate to hypothesize that the main source of these bacteria for humans are foods such as yogurt and cheeses. In this perspective, fermented foods rich in lactic bacteria can also be considered as "potentially and naturally functional".
Lactic acid bacteria (also called lactic ferments in the most common language) are among the most studied microorganisms. They are responsible for obtaining by fermentation many foods such as yogurt, cheeses, traditional leavened bakery products, fermented meat or vegetable products. The fermentation processes have been studied for over a century, that is since the practice of fermenting food began as a strategy for the conservation of milk, meat and vegetables. The role of lactic bacteria is to transform raw materials, and to contribute their metabolic activities to the rheological and sensory characteristics of the food. In other words, there would be no yogurt or cheese without the action of these important microorganisms.
Many strains belonging to species of lactic acid bacteria are also studied and marketed as probiotics, the most common belonging to genus Lactobacillus. Probiotics are the subject of considerable interest thanks to their potential to add functional properties to certain foods or to their use as food supplements for different purposes.
The good news is that the majority of fermented foods contain several thousand (often hundreds of thousands) of live lactic bacteria which are then ingested at the time of consumption of yogurt, cheeses etc. Some of these may contain probiotic bacteria naturally present in raw materials or selected during food production. Therefore, many fermented foods could be "naturally functional"Because they contain high levels of lactic acid bacteria, some of these potentially probiotic.
Overcome the gastric barriers, how many of these microorganisms reach the intestine? And how many go to the large gut microbiome community?
Some scholars belonging to the research group of Professor Ercolini of the Department of Agriculture and to the University Task Force for Microbiome Studies, in collaboration with other European partners, like the Teagasc (Agriculture and Food Development Authority, Ireland) and CIBIO of the University of Trento, have analyzed hundreds of thousands of genomes to try to answer these questions. The study was conducted as part of the MASTER (Microbiome Applications for Sustainable food systems through Technologies and Enterprise) project, one of the main EU funding for the Horizon 2020 Microbiome studies (www.master-h2020.eu).
Through modern computational analysis algorithms, genomes of lactic acid bacteria have been reconstructed from about 300 foods and nearly 10.000 human biological samples from different continents, verifying the distribution of lactic acid bacteria based on geographical origin, age and lifestyle of the subjects involved. In general, the researchers found a variable prevalence, dependent on the level of westernization in the lifestyle, and a relatively low abundance of lactic acid bacteria in humans especially when compared with the highest levels of the other members of the intestinal microbiome. The lactic bacteria most frequently found are Streptococcus thermophilus and Lactococcus lactis, very commonly found in yoghurt and cheeses.
In addition, around 3000 lactic acid genomes were compared: the high level of similarity of the lactic acid genomes from food and humans suggests that actually consuming foods rich in lactic acid bacteria can enrich our intestines with potentially probiotic microorganisms.
The study, just published in Nature Communications (https://doi.org/10.1038/s41467-020-16438-8) can open new horizons of study on fermented foods as potentially functional. Furthermore, the research offers ideas and methodologies for the development of appropriate and modern strategies for verifying the efficacy of probiotic bacteria in relation to their ability to permanently join with the human intestinal microbiome.