DuPont Challenge Science Essay Competition

Got Bugs? The Promise of Human Microbiome

by Meera Ramakrishnan

Winsor School
Boston, Massachusetts
Sponsoring Teacher: Tonya Rawlings

Second place, junior division, 2011

Imagine a world where you could consume a special yogurt to cure obesity or take a vaccine for diabetes. That utopian concept is quickly becoming reality as we begin to deepen our understanding of the symbiotic relationship humans have with the microbes in their bodies.

Humans have been battling with bacteria, or microbes, for thousands of years. Bacteria have been viewed as enemies in the fight for better human health. However, this past decade has seen a dramatic shift in our thinking. Were beginning to realize that many of these microbes are really our friends. As the Nobel Laureate in Medicine, Joshua Lederberg, observed, We are not just human beings but human-microbe hybrids or super-organisms, dependent on a vast number of microbes that cohabitate our bodies (Lederberg 287).

The insight that the humans and their microbial guests are symbiotically related has major implications. We are beginning to appreciate this special connection and how it affects obesity, drug metabolism, and ailments as diverse as autism, colon cancer, Crohns disease, diabetes, and psoriasis.

Microbes live in all parts of the human bodythe intestines, the skin, the nose, the mouth, the throat, the respiratory tract, and the elbows. Human guts are full of bugs that help digestion, provide 10% of our calories by breaking down dietary fibers we cannot process ourselves, and synthesize vitamins. They also stop disease-causing bugs from invading our bodies. Our bodies provide microbes with a diversity of habitats, much like the multitude of landscapes on Earth. The damp rainforest of our armpits, the anaerobic swamp of our gut, and the dry surface of our elbows recruit unique populations of bacteria (Everts 33). Collectively, they are known as the human microbiome. Their numbers are massive: 100 trillion microbes live in the average human. Given that our body contains only 10 trillion cells, were 10% human and 90% microbe!

The human microbiome plays an important role in metabolic processes. Professor Jeffrey Gordon of Washington University in Missouri found that transplanting gut bacteria from overweight mice into normal-sized mice caused them to eat more and gain weight. Later studies showed that both obese mice and obese people have fewer Bacteroidetes bacteria and a high proportion of Firmicutes bacteria in their intestines than their lean counterparts (Turnbaugh 2006 1027). These findings suggest that changes in gut microbiota due to shifts in diet or the environment may be responsible for the recent global obesity epidemic.

Microbiome seem to greatly influence the development of our immune system. By interacting with immune cell receptors, they cause the production of certain immune system cells. For example, an abundance of the gut bacterium Faecalibacterium prausnitzii, proven to have anti-inflammatory properties, seemed to help protect against the recurrence of Crohn's disease, an inflammatory bowel disorder (Manichanh 205). In another study, inserting bacteria taken from healthy guts into patients infected with Clostridium difficile restored the microbial communities, magically curing chronic diarrhea. Pioneering research by Sydney Finegold of UCLA showed that nine species of Clostridium histolyticum bacteria are present uniquely in autistic children, suggesting a link between gut microbiome and autism (Finegold S6).

While the recent discoveries to find a cure for life altering diseases are encouraging, plenty of big unknowns and multiple challenges remain in our quest to harness the power of the human microbiome. First, scientists are still unsure just how and when these communities of microbes colonize themselves in the body. The human microbiome seems to vary in response to diet, health, environment, and even the time of day. As a result, multiple samples of multiple subjects at various times are needed to get an accurate picture of whats going on. Second, the microbes are mostly anaerobic, meaning that they live without oxygen, and do not survive outside of the human body. Only 20% of them are culturable; therefore, DNA sequencing and other complex techniques are required to characterize the structure of microbial communities (Zhao 185). While the cost of sequencing is dropping, it is a long and cumbersome process, given the number of tests that need to be conducted. In the gut alone, as many as 1000 species bring to the body 100 times as many genes as our own DNA. Lastly, new bio-informatic tools are needed to analyze the flood of new data from the experiments and to allow scientists to draw conclusions. To address these challenges, several large-scale projects to catalog the diversity and activities of our microbial families have begun. One of the best known, the National Institute of Healths Human Microbiome Project (HMP), has been initiated to map out how an individual's personal microbial signature relates to health and disease (Turnbaugh 2007 804). The HMP is modeled after the Human Genome Project and promises to yield profound insights.

Despite the challenges, the potential healing power of microbiome is significant and untapped, motivating us to pursue this difficult science. The human genome cannot be altered, but our microbiome can be manipulated. Thus, in the future, we may be able to reconstitute the body's microbial profile to improve human health and fight diseasethis might include drugs, diets, probiotics, and functional foods that encourage the right bacteria to grow. We can imagine a time when each of us will be screened for native microbiota and given immunizations to fill in important missing bacteria. You are what you eat may have a deeper meaning than in the past, as meals could become more like a course of sumptuous medical treatment. Food labels and restaurant menus will soon include bacterial information. Indeed, ­ome cooking will become more important than Home cooking!

The progress in our understanding of the human microbiome is a great example of how break-through discoveries in science often require knowledge of, and advances in multiple disciplines. The new field of Human Microbiome, by integrating microbiology, medical science, and bio-informatics, holds the promise to diagnose and cure a range of diseases and fundamentally change the face of 21st-century medicine.

How exciting is that?

Sources

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