Obesity-associated microbiome has increased capacity to harvest energy from food.

Our recent discussion in class about obesity and the microbiome has spurred my interested in the idea of the bacteria that are associated with obesity being more able to extract energy from the food that people eat. This study specifically speaks about this happening in mice, where the microbiota of an obese individual, where the ratio of Firmicutes to Bacteroidetes is higher, is better able to extract energy from a specific diet than lean mice. One piece of evidence they pointed to that showed this idea was the result of a bomb calorimetry test, which showed that the faeces of the obese mice had significantly less energy remaining in them than did the faeces of lean mice. In this study, the transplanted the microbiota from the caecum of either lean or obese mice into germ-free mice.   After a 14-day period, there was no significant difference between the two groups of recipients in the measures of chow consumption, initial body fat, or initial weight of recipients. However, the results did show a statistically significant difference in increase in body fat over the two week period. These results suggest that an increased capacity for energy harvest in at least one type of obesity-associated gut microbiome. 

This article was really interesting to read in that it does provide some evidence that shows that some types of gut bacteria are better able to extract calories from the food that we are taking in. However what I found equally interesting was that the gut microbiomes of the lean and obese mice were able to be transplanted to the germ-free mice. This made me think about the discussion we had about how similar our microbiomes can become to those people we spend a lot of time around. Is it possible that if someone lives with either a lean or obese person, their lean or obese gut microbes could influence the gut microbiome of the person they’re living with? The idea that the gut microbiome can be transplanted also leads me to wonder what type of treatment options are available to help shift the microbiome of people with obesity. 

Turnbaugh, P.J., Ley, R.E., Mahowald, M.A., Magrini, V., Mardis, E.R., Gordon, J.I. (2006) An obesity-associated gut microbiome with increase capacity for energy harvest. Nature 44: 1027-1031. 



More Microbes From Mom: Bacteria in Breast milk

After discussing the effects of c-section on the microbiome that an infant receives from its mother, I wondered in what other ways the mother affects the infants microbiome. To investigate this, I looked at whether or not breast milk had any effect on the baby’s microbiome. As it turns out, there are bacteria in breast milk that are transferred from the mother to the baby. This is a new and interesting discovery, as it was previously thought that breast milk was sterile. So where does this bacteria come from? Part of it comes from the baby, as there is some flow-back from the babies mouth as it drinks from the nipple. However it is suggested that the rest of this bacteria is transferred by immune cells, specifically dendritic cells, from the gut to the breast. While there is still more research to be done, this hypothesis of the bacteria from the gut being transferred to the breast milk seems to be the most promising. It appears that the bacteria that babies receive from their mother’s breast milk replace the gut bacteria they received during the birthing process. 

I think that this article raises a lot of interesting questions about the importance of breast milk in a baby’s development from the perspective of building their microbiomes. The first thing that I am curious about is how important this bacteria from the breast milk is to the development of the baby. If it is super important, how do we ensure that mothers who are able are breast feeding their babies? Also, what happens if the mother is unable to breast feed their baby, or if the mother is prescribed antibiotics while breast feeding? Is there a way to supplement babies whose mothers are unable to breast feed them? Also, how would antibiotics prescribed to the baby effect their ability to acquire a microbiome from their mother? The discovery that breast milk contains bacteria raises many questions about how this affects the baby that I believe could spur much future research. 


Gould, S.E. “The bacteria in breast milk.” Lab Rat. Scientific American, 8 December 2013. Web. 27 April 2014. 



Modern medicine and the microbiome



This NPR interview with Dr. Martin Blaser, who directs the Human Microbiome Project at NYU, really grabbed my attention because it addresses a wide range of issues that are linked to the interaction between the human microbiome and some aspects of modern medicine. As someone who is interested in medicine, I believe that it is important for doctors to understand how their decisions about a patient’s course of treatment could affect the patient’s health by altering the microbiome, as is discussed by Blaser. Blaser discusses the idea that antibiotics increase a patient’s risk for obesity because it alters the gut microbiome. Blaser also discusses that babies born by c-section do not begin developing their microbiome from their mother’s birth canal, but instead receive exposure to a skin microbiome. Blaser suggests that babies receive lactobacilli, bacteria that help to break down lactose – the main component in milk, from the birth canal, which helps to build the foundation for the babies’ gut microbiome. He suggests that a study showed that children born by c-section were more likely to have increased fat than naturally born children.

It seems to me that the idea here is that medical advances such as the use of antibiotics to treat disease and c-sections to keep at-risk mothers safe during child birth are causing potentially harmful changes to our microbiomes. However, this is part of what makes me struggle a little bit with this article. These advances in medicine, antibiotics and c-sections, seem to be life-saving practices helping people to overcome bacterial disease and mothers to survive complicated births. But, as this interview suggests, these potential life-saving practices may have health consequences. So how do we balance the harm that is done to people receiving treatment? At this point, it seems that interventions such as antibiotics and c-sections can be crucial in helping people, and so these are things we cannot get rid of. However, I hope that it is possible that future research can be done to help find other interventions for these ailments, or to help to lessen their negative effects. In the meantime, I believe that it would be useful for doctors to at least become more aware of how often they prescribe antibiotics, in order to lessen the occurrence of these harmful effects. This would include determining if infections are caused by bacteria or viruses, in order to reduce the longterm costs of prescribing antibiotics when they are not necessary.


Blaser, Martin. “Modern medicine may not be doing your microbiome any favors.” Interview by Terry Gross. Fresh Air. NPR. 14 April 2014. Radio.