The Science of Sustainability

The Human Microbiome: A Rogue's Gallery

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Scientists are starting to get a handle on what kinds of microbes live in the human body and, roughly, how those populations differ from one individual to another. A key question now is whether there is such a thing as an “ideal” microbiome. In the meantime, get to know some of the microbes that may be in your gut.

H. pylori has lived in our stomachs for 200,000 years. (Photo: Yutaka Tsutsumi)

H. pylori has lived in our stomachs for 200,000 years. (Photo: Dr. Yutaka Tsutsumi)

Helicobacter pylori

Humans have a love-hate relationship with H. pylori. It has dwelled inside our stomachs for 200,000 or so years, but its role is unclear. Scientists believe the microbe causes peptic ulcers and have linked it with an increased risk of stomach cancer. But the percentage of people with H. pylori has been shrinking, particularly in the Western world where antibiotic use has been widespread for more than half a century. Those lacking in H. pylori may be at higher risk for asthma or obesity, since the bacteria helps tell us when we’re full. Scientists aren’t sure whether the absence of the microbe actually causes asthma or obesity, but the two occurrences do correlate.

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C. difficile can cause some nasty problems if left unchecked by "good" bacteria. (Photo: Centers for Disease Control)

C. difficile can cause some nasty problems if left unchecked by "good" bacteria. (Photo: Centers for Disease Control)

Clostridium difficile

The “good” bacteria in your gut often keep bad stuff at bay. When the good guys are destroyed (possibly with antibiotics), C. difficile takes over, which can cause severe diarrhea or deadly inflammation of the colon. The condition most commonly affects hospitalized older adults or those in long-term care. The cure: more antibiotics — or a fecal transplant.

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Bifidobacterium

Bifidobacterium lives throughout the body and can be damaged by antibiotic treatments. (Photo: Wikimedia Commons)

Bifidobacterium lives throughout the body and can be damaged by antibiotic treatments. (Photo: Wikimedia Commons)

The gut biota ecosystem is a dramatically changing environment in the first two years of life. Bifidobacterium include a range of bacteria species that exist symbiotically throughout our bodies. But the evolution of Bifidobacterium in infant bodies can be stunted by early antibiotic treatment. The bacteria are linked with many probiotic benefits, and scientists do not yet understand the long-term health consequences of reducing their numbers.

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P. gingivalis can make your teeth fall out. (Photo: Flickr user AJC1)

P. gingivalis can make your teeth fall out. (Photo: Flickr user AJC1)

 

Porphyromonas gingivalis

Did you brush your teeth this morning? The microflora in our mouths can cause some real problems. Take P. gingivalis (pictured). The bacteria places a role in the onset of periodontitis, an inflammation of the gums that causes teeth to fall out. P. gingivalis is also associated with rheumatoid arthritis and heart disease. It’s less abundant in the mouth than, say, Streptococcus parasanguinis. Those bacteria colonize the surface of your teeth, forming plaque.

 

 

 

 

 

 

 

 

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Sean Greene

About the Author ()

Sean Greene was an intern for KQED Science. He is a proud alumnus of UCLA (2011) and the Daily Bruin and is now a student at the UC Berkeley Graduate School of Journalism. Before moving to the Bay Area, he freelanced for the Ventura County Star and The Orange County Register. Each story is an adventure, and the best ones are those that get him outside and exploring new places.