By Mangurleen Kaur, Biological Science, 23’

Author’s Note:  In one of my classes of basic biology, I got to learn about microbes. That class discussed some relationships between microbes and between human beings. One of the points that stuck in my mind was the relationship of microbes between humans and one of our favorite pets, dogs. By researching this topic, I found it so astounding that I decided to write about it. I hope this piece will be interesting not only for science-lovers but also for the general public.  

Both, inside and out, our bodies harbor a huge array of microorganisms. These microorganisms are a diverse group of generally minute life forms, which are called microbiota when they are found within a specific environment. Microbiota can refer to all the microorganisms found in an environment including bacteria, viruses, archaea, protozoa, and fungi. Furthermore, the collection of genomes from all the microorganisms found in a particular environment is referred to as a microbiome. According to the Human Microbiome Project (HMP), this plethora of microbes contribute more genes responsible for human survival than humans contribute. Researchers also estimated that the human microbiome consisted of 360 times more bacterial genes than human genes. Their results show that this contribution by microbes is critical for human survival. For instance, in the gastrointestinal tract bacterial genes are present, which allow humans to digest and absorb nutrients that otherwise would be unavailable. In addition to this, microbes also assist in the synthesis of many beneficial compounds, like vitamins and anti-inflammatory agents which our genome cannot produce. (4)

Where does this mini-ecosystem start from? The microbiome comes in our body as soon as we come out from the mother’s womb, we acquire them from the mother’s vagina and then, later on, by breastfeeding which plays a great role in making the microbes’ own unique community. There are several factors that influence the microbiome which include physiology, food, lifestyle, age, and environment. These are not only present in humans, but also in most animals and play a significant role in their health. For instance, gastrointestinal microorganisms exist in symbiotic associations with animals. Microorganisms in the gut assist in the digestion of feedstuffs, help protect the animal from infections, and some microbes even synthesize and provide essential nutrients to their animal host. This gives us an idea of how important these microorganisms are to our living system as a whole.(3)

Besides the human’s strong emotional connection with the dogs, there is also a biological relationship between the human and dog’s interactions. In context of this interesting relationship, research has been conducted. Computational biologist Luis Pedro Coelho and his colleagues at the European Molecular Biology Laboratory, in collaboration with Nestlé Research, studied the gut microbiome (the genetic material belonging to the microbiota) of beagles and retrievers. They found that the gene content of the dog’s microbiome showed more similarities to the human gut microbiome than to the microbiomes of pig or mice. When researchers mapped the gene content of the dog, mouse and pig microbiome in contrast to the human gut genes, they found that respectively 63%, 20% and 33% overlapped.(5) This shows the extensive similarities between human and dog’s gut microbiomes in comparison to other animals. Speaking on the discovery, Luis Pedro Coelho says: “We found many similarities between the gene content of the human and dog gut microbiome. The results of this comparison suggest that we are more similar to man’s best friend than we originally thought.” (1)

The University of Colorado Boulder did a study on the types of microbes present on the different parts of humans, to better understand the diversity and its significance for the human’s body. They conducted the study on 60 American families in which they sampled 159 people and 36 dogs. The team took samples from tongue, forehead, right and left palm and fecal samples to detect individual microbial communities. Through research, the researcher learned that people who own dogs are much more likely to share the same kinds of these “good” bacteria with their dogs. They have also learned that children who are raised with dogs are less likely than others to develop a range of immune-related disorders, including asthma and allergies. “One of the biggest surprises was that we could detect such a strong connection between their owners and pets,” said Knight, a faculty member at CU-Boulder’s BioFrontiers Institute.(6) The results found that adults who have a dog and they live together, share the greatest number of skin phylotypes while adults who neither have a dog nor live together share the least. 

The University of Arizona is also conducting another research study, with some other universities including UC San Diego, in which they are seeking healthy people from Arizona age 50 or older, who have not lived with dogs for at least the past 6 months. Then they are selecting persons who would like to live with the assigned dogs. The goal of the study is to see whether the dogs enhance the health of older people and work as probiotics (good bacteria). But this research is ongoing and the outcomes are not yet released. Rob Knight, Professor of Pediatrics and Computer Science & Engineering at UC San Diego and his lab studied microbiomes. Knight and his team found that the microbial community on adult skin are on average more similar to those of their own dogs than to others. They also found that cohabiting couples share more microbes with one another if they have a dog, compared with couples who don’t have a dog. Their research suggests that a dog’s owner can be identified just by analyzing the microbial diversity of the dog and its human, as they share microbiomes. These studies are finding a critical relationship that is very helpful in microbiology and the overall health field in science. (2) 

These studies reveal the various interesting relationships of microbiomes with us and other living beings. So far, the studies discussed how dog’s microbiomes are shared by the owner and how gene sequencing helps us to understand these connections. The growing understanding of this connection with microorganisms raises many other outstanding questions like what are the health benefits of a dog to a human? How can they help in preventing certain chronic diseases? This represents an exciting challenge for scientists and researchers to refine their understanding of microbiomes and find answers to these further emerging questions.

Work Cited

1. “NIH Human Microbiome project defines normal bacterial makeup of the body”. National Institutes of Health, U.S. Department of Health and Human Services. www.nih.gov. Published on August 31, 2015. Acessed May 10, 2020
2. Ganguly, Prabarna. “Microbes in us and their role in human health and disease”. www.Genome.gov. Published on May 29, 2019. Accessed May 10, 2020.
3. “Dog microbiomes closer to humans’ than expected”. Research in Germany, Federal Ministry of Education and Research. www.researchingermany.org. Published on April 20, 2018. Accessed May 11, 2020.
4. Trevino, Julissa. “A Surprising Way Dogs Are Similar to Humans.” www. Smithsonianmag.com. Published on April 23, 2018. Accessed February 11, 2020.
5. Song, Se Jin, Christian Lauber, Elizabeth K Costello, Catherine A Lozupone, Gregory Humphrey, Donna Berg-Lyons, Gregory Caporaso, et al. “Cohabiting Family Members Share Microbiota with One Another and with Their Dogs.” eLife. eLife Sciences Publications, Ltd. elifesciences.org. Published on April 16, 2013. Accessed May 11, 2020. 
6. Sriskantharajah, Srimathy. “Ever feel in your gut that you and your dog have more in common than you realized?” www.biomedcentral.com. Published on April 11, 2018. Accessed February 11, 2020.