Although we try to side-line bacteria throughout the entire food chain, they do in fact play an important part in the final few metres. In the human intestine, thousands of different types of bacteria that form our intestinal microbiota (previously called intestinal flora) release carefully cultivated, harvested and processed nutrients into our body. This complex ecosystem is gradually revealing its secrets.
Why does one person falls ill from a Salmonella infection while another feels fine? What are the chances that someone will become obese? The answers to these and many other questions can be found by understanding the system that organises human resistance and food intake. This system is the intestinal system; a complex ecosystem comprised almost entirely of bacteria. An estimated 90 percent of cells in the human body is bacterial and lives in the intestine. They are the object of a study by a team of biotechnologists, micro biologists, biochemists, bacteriologists, geneticists and medical biologists at Wageningen UR headed by Willem de Vos, professor of microbiology.
The discovery that the ecosystem of intestinal bacteria determines the (non-)development of diseases is relatively recent. In the past, physicians have regarded many diseases as an infection by certain pathogens such as Salmonella or E. coli bacteria. Treating the disease starts with removing the infection. Now there is a growing realisation that it is the level of disturbance of the existing intestinal system by the intruder that determines whether someone will or will not suffer permanent discomfort. Sometimes the pathogen is able to disrupt the system, but often the system stands firm or recovers quickly. By getting to know the interaction between the intruder and the existing system, we will be able to control a number of diseases in a more effective, and possibly less expensive way.
Connected in consortia
The intestinal microbiota do not simply consist of a collection of individual bacteria. The bacteria are connected in consortia that are jointly responsible for the complex process of converting food into fatty acids, vitamins and other useful substances, transportation through the intestinal wall to the cells, the dis charge of waste products, and resistance to foreign and toxic substances. Researchers of Wageningen UR recently discovered that they play a role in a number of diseases. Intestinal microbiota work together in various ways and have countless signal transduction systems with which they exchange information with each other and their environment. Part of this environment are the host cells that allow communication with the human body. The communication between bacteria makes the collective stronger than the sum of its parts.
In their research the scientists approach the consortium as if it were a single organism. They used meta-genomics to map the total genetic functionality of the intestinal microbiota without having to unravel the genome of all individual bacteria. The European research programme MetaHit, in which Wageningen UR is a participant, served as a precursor. In addition, the Wageningen scientists worked with systems analysts from Helsinki University to realise a meta-analysis of the intestinal microbiota in over five thousand human subjects. The resulting data was collected in a large databank and subjected to extensive analyses. This offered a clear picture of unique compositions of intestinal microbiota (not two single persons have an identical collection of bacteria) with recognisable patterns.
These patterns provide insight into the functioning of the consortia and help predict the effects of changes to the bacterial composition. The analysis supports the hypothesis that people inherit two things from their mother at birth. In addition to the DNA as a genetic unchangeable code, a baby inherits intestinal bacteria from the person who has most contacts in early life; usually the mother. Other research has shown that this collection of bacteria generally remains stable throughout a person’s life. If the hypothesis is correct, metabolic diseases like diabetes and obesity can be predicted by means of the intestinal microbiota.
Moreover, the knowledge that the healthy intestinal microbiota is relatively stable over at least a decade makes it possible to recognise and repair disruptions and imbalances at an early stage. We might be able to tackle the major disruptions that currently still lead to chronic diseases, such as inflammatory bowel disease (Crohn’s disease and colitis ulcerosa), by supplementing the shortage of bacteria with a so-called faecal transplant. Researchers in Wageningen and Amsterdam have shown this to work efficiently in Clostridium difficil infections as recently published in the medical leading journal the New England Journal of Medicine.
Recovery intestinal system
Supplementing bacteria may seem like drinking over-the-counter probiotics with lactobacilli. But, whereas probiotics can at most provide healthy people with a boost, faecal transplants involve a medical procedure for sick people with an extreme imbalance. An example of such a disease is obesity. Obese people consume more calories from food than they require and store it as fat reserves. As with people who don't absorb enough calories, this is related to a disruption of their insulin resistance. A faecal transplant could result in a durable recovery of the intestinal system for both groups and could complement programmes based on changing dietary or exercise patterns.
Research is also currently being performed into the functioning of the intestinal microbiota in relation to dietary patterns and medicinal use. The first impression is that the dietary pattern, especially in the early years, can affect the intake of nutrients and possibly even the development or intensification of obesity. The repeated use of antibiotics may also be an important factor. The exact relations are not yet entirely clear, however. The knowledge of intestinal microbiota is currently rapidly developing and has unprecedented potential. It can possibly help people grow older in a healthier way, and limit obesity, inflammatory bowel disease, or irritable bowel syndrome. The knowledge may also be used to develop alternative nutrients. The general concepts that are being developed could also help improve nutrient intake and general health outside of the wealthy Western world, but the technology is yet too expensive to apply on a global level.
In addition, knowledge is being collected on the intestinal microbiota of production animals with an eye on using the resulting insights in breeding to improve the health of pigs, cattle and poultry. A major project was recently established in partnership with TI Food & Nutrition, for example, looking into reducing methane production from cattle and thus increasing the food conversion efficiency in the cows themselves. A larger understanding of intestinal microbiota in animals and humans can result in a better intake of food and thus limit the primary food demand. At least as important is the possible effect of the research on our health and quality of life."