Molecular Dialogues of the Microbes Inside Us

(Source)

         Professor Guillemin’s talk at the Microbes of the Modern World lectures inspired awe in listeners about the microbes within us.  While many people think of pathogens that cause diseases in people when they hear the word “microbes”, Professor Guillemin’s work with the Human Microbiome Program illustrated how integral microbes are for the function of our body.  She opened her lecture by providing some context for the influence that microbes have on the human body: there are more cells of bacteria in the gastrointestinal tract than there are cells in the entire body.
  
           The Human Microbiome Program works to survey the micro-organisms throughout the human body.  They look note the differences in composition of these microbes at different locations throughout the body.  Data by the HMP has found that people have completely distinctive microbial communities, as distinctive as fingerprints.  This individuality raises several questions for further research:
            -    What factors determine microbial composition?
            -    How stable is the gut microbial community (is it stable over a person’s lifetime?
                 Across generations?)
            -    Can changes in microbial communities cause disease?

Graph showing microbial composition of babies based on
method of birth

            A human baby is sterile or without microbes until it is born.  As you can see from the graph, the composition of a baby’s microbes is determined by the method by which it is delivered.  A baby that was born vaginally has microbes similar to that of its mother’s vagina whereas a baby born via cesarean section has a microbial composition similar to the skin of the mother as well as the skin of the doctors and nurses present in the operating room.  Additionally, it has been found that microbial communities change as a diet changes.  It has even been found that breast milk contains sugars that specifically support growth of particular microbes.  These data suggest that microbial composition is determined by a person’s exposure to people, environments and even diet.

           Another important issue to examine was whether altered microbiota communities cause disease or are merely a consequence of it.  Through the use of model organisms, such as zebrafish, Guillemin can look for possible sources of causation.  Characteristic shifts in communities have already been associated with specific diseases.  This could have important implications as disease could soon be seen as changes in microbial communities.

Zebrafish: the model organism (source)

             One important feature that makes the model organism zebrafish prime for research on microbes is that they can be reared sterile and then have microbes introduced into their systems.   This allows researchers to determine whether differential microbial communities cause symptoms, such as inflammation, or are a consequence of these symptoms.  Guillemin’s lab looked at a mutant fish that had difficulty clearing their gut of old microbes from their food also tended to have an inflamed gut and increased concentrations of immune cells.  By using germ-free fish, they found that inflammation was actually caused by the different microbiota.  This data suggests that different microbiota might actually drive disease or cause transmissible intestinal inflammation.  Learning about the important impact that microbiota can have on human health inspires us to learn to nurture our internal microbes as well as the microbes found in the environments we live in. 

Sources cited:

 Guillemin, Karen. "Molecular Dialogues with the Microbes inside Us." Microbes and the Modern World: From the Globe to the Gut. Lillis Business Complex, Eugene, OR. 29 May 2012. Lecture.