We tend to think of ourselves as ourselves: a collection of DNA-directed human cells that make up our bodies and carry out life’s important processes. Only we need help. A lot of help. In sheer numbers of cells, we’re arguably more parts bacteria and other microbes than human. That universe within is called the microbiome— actually multiple microbiomes inhabiting different parts of the body. Without them, we couldn’t live.

Science is just now getting a handle on the body’s microbiomes and their surprising impacts on human health. It’s not easy work.

“We’re studying the whole complexity of the human body. We’re also studying the whole complexity of billions of microbes of hundreds of different species—each one of them with their own genes and their own proteins,” says Jotham Suez, PhD, MSc, an assistant professor in the W. Harry Feinstone Department of Molecular Microbiology and Immunology.

Teasing meaning from that complexity, researchers are already overturning assumptions about disease susceptibility, drug effectiveness, and other issues. One example: Suez found that probiotics can have positive, negative, or no effects on an individual, depending on how their microbiome responds to the probiotics.

Working on this new frontier, scientists are gleaning new microbiome insights for improving human health.

The Universe Within

ORAL MICROBIOME

Hundreds of bacteria species live in the human mouth, creating the most diverse microbiome after the gut. Intrigued by findings that connect periodontal disease and adverse pregnancy outcomes like preterm birth, Daniel Erchick began gathering oral microbiome samples in rural Nepal. Data from that research may help lead to interventions promoting healthy oral bacteria that could, in turn, improve outcomes for mothers and their infants.

VAGINAL MICROBIOME

“There are so many questions,” says OB-GYN Anne Burke of the vaginal microbiome. Though it isn’t as diverse as the gut microbiome (<500 species vs. >30,000), it remains a difficult research challenge. Other complicating factors: hormonal contraceptives and antibiotics that dramatically alter the vaginal microbiome. So, Burke, Laura Ensign, and Khalil Ghanem are working together to understand their effects on reproductive and sexual health.

COLON MICROBIOME

A global surge in early-onset colorectal cancer has Cynthia Sears worried … and working. Knowing that just 15% to 30% of individuals respond to immunotherapy to treat cancer, Sears wants to up the odds of treatment success. Monitoring the microbiomes of 400 patients throughout their treatment, Sears is seeking ways to boost organisms in the colon that promote immunotherapy and dial down microbes that hinder the treatment.

SMALL INTESTINE MICROBIOME

Sugar substitutes may seem harmless, but they can promote risky changes to one’s gut microbiome. In ongoing research, Jotham Suez is finding that noncaloric sweeteners can disrupt the microbiome and lead to elevated blood glucose and increased risk for type 2 diabetes in some people. Suez is now trying to understand the mechanisms involved and ultimately devise diagnostics that can show who should avoid the faux sugars.

LARGE INTESTINE MICROBIOME

Microbes thrive in the small and large intestines, covering mucosal surfaces and interacting with human immune cells. Subhra Chakraborty wants to know if that microbial swarm determines an individual’s susceptibility to disease. She’s studying whether subtle changes to microbe populations could boost immunological protection against enteric diseases—and possibly even neurological and respiratory illnesses.

RECTAL MICROBIOME

Can the rectal microbiome be a new target for preventing STIs? It’s an important question: Rectal STIs have been associated with an increased risk of HIV infection. Susan Tuddenham is seeking answers by analyzing samples from a cohort of Nigerian men who have sex with men. She’s also addressing a weakness in the current science: Most rectal microbiome samples in MSM are from the U.S. and Europe.

Sources: Anne Burke, MD, associate professor, Obstetrics and Gynecology in JHSOM and Population, Family and Reproductive Health; Subhra Chakraborty, PhD, MPH ’13, MSc, associate scientist, International Health; Laura Ensign, PhD, associate professor, Ophthalmology, and Obstetrics and Gynecology in JHSOM; Daniel Erchick, PhD ’17, MPH ’12, assistant scientist, International Health; Khalil Ghanem, MD, PhD ’08, professor, Medicine in JHSOM and PFRH; Cynthia Sears, MD, professor, Medicine in JHSOM and Molecular Microbiology and Immunology; Jotham Suez, PhD, assistant professor, MMI; Susan Tuddenham, MD, MPH ’09, associate professor, Infectious Diseases in JHSOM and Epidemiology

Meet Your Microbiomes