Microbiome And Its Relationship To Health

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microbiome relationship to health

Microorganisms are life forms that are so small we cannot see them with the naked eye; we need a microscope to see them. Microorganisms live in all habitats, and some of them are best known for their ability to make us sick. For example, human pneumonia is often caused by the bacterium Streptococcus pneumoniae, and food sickness can occur after ingesting certain types of Escherichia coli or Salmonella. In any given habitat, such as a lake, gram of soil, or animal gut, there are billions or trillions of microorganisms all living together as a community. The collection of these microorganisms within a specific habitat is known as the “Microbiota.” Different types of life forms can be part of the microbiota, including bacteria, fungi, and some tiny plants and animals.

Each member of the microbiota has its own collection of genes. Just as in humans, genes are the instruction set for making and maintaining individual organisms. Each microbial species has its own set of genes. The collection of genes within the microbiota is the microbiome. This collection of genes is vast and, in the human gut habitat, outnumbers the number of human genes1. Scientists can “read” these microbial genes using sequencing techniques to identify the microbial community in a given habitat.

Microbiome relationship to overall health

One habitat teeming with microorganisms is the animal gut. All animals, including humans, pets (dogs, cats, etc.), domesticated livestock (cows, sheep, etc.), and wild animals (hawks, deer, spiders, etc.) support an incredible number of microbes in their guts. In fact, current estimates suggest that the number of microbial cells in the human gut is approximately equal to the number of human cells2. Without these microbes, animals would be unable to digest all of their food or develop a fully functional immune system.

The microbiome has an extremely wide impact on health

Microbes living in and on animals can affect animal health in a variety of ways. Some microbes are essential for health. For example, in the gut, microbes assist with digestion3. On the skin, microbes may be important for preventing allergy4. In contrast, some microbes are not good for health, potentially making an animal sick, or in the case of microbes living in the mouth, may affect the development of periodontal disease5,6. Although microbes with these extreme effects exist, most microbes are somewhere in between: some of them are slightly beneficial, some of them have no effect at all, and others are partially detrimental but not bad enough to make the animal sick. This gets even more complicated when we think about microbes affecting each other and how those microbial interactions may change the outcome with respect to animal health. For example, microbe X may help with food digestion only if microbe Y is absent. However, if microbe Y colonizes the gut, microbe X produces a toxin to kill microbe Y, and this toxin inadvertently causes inflammation of the intestinal walls.

Conditions that affect gut health

According to recent studies, disruptions to microbiota, often referred to as “dysbiosis,” may play a role in the development of several conditions, including Inflammatory Bowel Disease (IBD)7-10, allergies4,11, obesity12, periodontal disease5, and diabetes13. Disruptions may be caused by many factors, including antibiotic usage, dietary changes, and stress14-16. For example, even though antibiotics have been essential for prolonging life by controlling infectious diseases, they also wreak havoc on the microbiota because they will kill innocent microbial bystanders in addition to the microbe causing disease. This can alter the abundances or presence of particular microbes in the gut, thereby disrupting the normal function of the gut microbiota. Other disruptions work similarly by upsetting the normal balance of microbiota. As more studies are conducted to identify the causes and consequences of disrupting the microbiota, scientists will be able to identify robust associations between changes in the microbiota and disease, and eventually identify effective treatments.   

Disrupting the microbiota is often unavoidable, and thus, in order to prevent loss of beneficial gut microbes, we need to do all we can to improve their ability to return their guts to a healthy, pre-antibiotic state.

Microbiome relationship to nutrition

The microbes in the gut help with digestion3, which means that they eat what their animal “host” eats. Thus, animal diet and nutrition has a strong impact on the gut microbiota17,18. Can an animal eat specific foods or nutrients in order to maximize the number of beneficial microbes living in their guts? Likewise, can specific foods reduce the numbers of detrimental microbes and/or steer microbial interactions to have outcomes that are favorable for animal health?

We cannot completely answer these questions until scientists conduct more research. But we do know that certain components of diet affect particular members of the gut microbiota in dogs and cats. For example, the amount of protein and carbohydrates that dogs and cats eat can steer the gut microbiota towards having more bacteria of the Firmicutes type19. Too much protein might negatively alter the gut microbiota and impact dog health20. Experiments with potato fiber in dog diets have shown that this fiber source resulted in “favorable fermentation,” butyrate production, and increased abundances of “good” gut bacteria21,22. Examining gut bacteria by “reading” their DNA sequences has now become much more affordable, paving the way for more studies to test particular dietary components for their effects on gut microbiota and overall health. Moreover, pet parents can also have the gut microbiota of their pets characterized in order to improve pet diet and overall health.


References

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  2. Sender R, Fuchs S, Milo R. Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans. Cell. 2016;164: 337–340. doi:10.1016/j.cell.2016.01.013
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