Interview with Dr. rer. med. Tewodros Debebe from Biomes
What is your favourite microbe and why?
All good microbes that are devoted to us and that play an important role in our well-being are my favourite microbes. But if I had to pick one specific bacterium I would go with Lactobacillus. Because Lactobacillus may benefit our health in several ways, such as reducing cholesterol, prevention or reduction of diarrhoea, improving symptoms of Irritable Bowel Syndrome (IBS), preventing vaginal infection, promoting weight loss, reducing common cold symptoms, reducing allergic reactions and eczema.
When was it discovered and by whom?
The genus Lactobacillus currently contains somewhat over 180 species. Each species of Lactobacillus was discovered at a different time. Nevertheless, the first Lactobacillus species was isolated in 1900 by Ernst Moro, an Austrian physician, from infant faeces and at the time it was designated as Bacillus acidophilus and later renamed to Lactobacillus acidophilus.
Do we know how long this microbe has been present on Earth?
An accurate statement on how long Lactobacillus species have been living on earth can hardly be made. However, as the members of Lactobacillus are associated with yogurt, which is produced by the bacterial fermentation of milk, Lactobacillus has been there at least since the origins of yogurt which is thought to have been invented around 5000 BC. Nearly every culture that has kept animals for milk has produced yogurt and it is likely that it was discovered in similar ways in different regions of the world. Even though people have used Lactobacillus for many years unknowingly, it was around 1900 that scientists started studying and isolating the bacteria that made yogurt. Lactobacillus acidophilus was then discovered by Ernst Moro, an Austrian physician, who examined the faeces of a child with gastrointestinal disorder.
In 1905, the Bulgarian Dr. Stamen Grigorov discovered a special kind of Lactobacillus in yogurt and called it Lactobacillus bulgaricus. Around 1907, Russian scientist Elie Metchnikoff who was interested in Dr. Grigorov’s discoveries, spent time in the remote villages of the Caucasus Mountains, where the majority of villagers lived longer compared to the general world population. Metchnikoff noticed the village centenarians were drinking a fermented yogurt drink on a daily basis, which contained a probiotic called Lactobacillus bulgaricus which may have helped to prolong their lives. Another scientist was a Japanese microbiologist named Minoru Shirota who was inspired by the work of Elie Metchnikoff and discovered a strain of Lactobacillus casei which he named Lactobacillus casei Shirota. Shirota believed that the production of lactic acid in the gut could destroy the bad bacteria in the intestines and thus improve the consumer’s health and prolong their lives. You may or may not have heard of Shirota, but the chances are high you’ve heard of his creation: the yoghurt probiotic drink Yakult, one of the first commercially available probiotics.
Which taxonomic level do we assign it to?
If we see the taxonomical hierarchy, Lactobacillus is at genus level and it is a major part of the lactic acid bacteria group (i.e. they convert sugars into lactic acid). Its name gives an indication of what it produces — lactic acid. It does this by producing an enzyme called lactase. Lactase breaks down lactose, a sugar found in milk, into lactic acid.
Where does it mainly occur in the human body?
In humans, Lactobacillus species constitute a significant component of the microbial community at a number of body sites, such as the digestive system, urinary system, and genital system. In women, Lactobacillus species are normally a major part of the vaginal microbiota. Lactobacillus exhibits a mutualistic relationship with the human body, as it protects the host against potential invasions by pathogens, and in turn, the host provides a source of nutrients.
Where in the environment and in which foods does it occur?
You can find Lactobacillus in and on plants and soil, but mainly in animal feeds, silage and manure. Members of Lactobacillus are the most common bacteria found in fermented food products such as yogurt and kefir. Various species of Lactobacillus are used commercially during the production of sour milks, cheeses, yogurt, and they play an essential role in the manufacturing of fermented vegetables (pickles and sauerkraut), beverages (wine and juices), sourdough breads and some sausages.
How can we enrich this microbe in our gut?
Normally, many Lactobacillus species belong to the microbial community in healthy intestines. However, Lactobacillus can also be enriched by the intake of Lactobacillus-containing probiotic supplements, either on its own or in combination with other probiotics or prebiotics. Furthermore, we can also get Lactobacillus from fermented foods and the best food sources of Lactobacillus are kefir, yogurt, sauerkraut, most types of cheese, miso and tempeh.
Can it be produced industrially?
Although a fairly complex process, it is possible to produce it on a large scale and under tightly controlled conditions. The common way is by mass cultivation of Lactobacillus in accredited laboratories, following international quality standards. The microbes are cultivated on a growth medium, the culture biomass is harvested and then undergoes the so-called lyophilisation (freeze-drying) which inactivates them. When they are exposed to a nutritious and benign environment such as a healthy gut they enfold and become active again. A number of Lactobacillus species are then used for probiotic dietary supplements either in the form of powder or capsules (containing the powder). Consumers can purchase them from the producer directly or in pharmacies. The quantity of the probiotic bacteria is indicated as CFU (Colony Forming Unit) and is used to quantify how many bacteria in probiotics are capable of dividing and forming colonies. It is a mouthful, but to make the long story short, think of CFU as one distinct bacterium.
As we already know, Lactobacillus is widely used in the food industry and fermented foods are available in almost every supermarket. This kind of fermentation process is usually made by using so-called starter cultures which is a mix of various microbes. Around 35% of the foods we consume are produced with the help of starter cultures.
What are their metabolites in the human intestine and what are they good for?
Lactobacillus species produce several beneficial products such as vitamins, enzymes, short chain fatty acids (butyrate, acetate and propionate), which have shown to exert multiple beneficial effects on human health and energy metabolism. For instance, by strengthening the gut lining, modulating the immune system and affecting our mental response through the gut-brain-axis. Interestingly, Lactobacillus species can produce a substance called Bacteriocin which inhibits the growth of bad microbes. In the vaginal flora, Lactobacillus species are very important in maintaining the vaginal ecology and preventing vaginal infections, usually caused by Candida, because Lactobacillus produces lactic acid as a metabolic product making the vaginal environment acidic so that bad microbes can’t survive in this environment.
Dr. rer.med. Tewodros Debebe
Dr. Tewodros Debebe is a medical microbiologist and since 2017 Head of Science at BIOMES – a Berlin-based biotechnology company specializing in microbiome analyses for end users and professionals. He earned his PhD in Medical Microbiology from the Faculty of Medicine at the University of Leipzig in 2017. Dr. Tewodros’s great passion is understanding the microbiota and the way it interacts with the human body. He has published more than ten scientific works in well-known peer-reviewed international journals, such as the Nature Scientific Report and PLoS ONE journals. Currently, his main role at BIOMES is developing a knowledge database on microbiota which is based on the latest scientific and clinical studies and serves as a basis for interpretation and recommendations.