There are more microbial cells than human cells in your body; this is a good thing. Bacteria help us break down foodstuffs by fermentation, synthesize vital molecules, and help us get rid of excess nitrogenous wastes. Furthermore, it has been demonstrated that the kind of bacteria you have in your gut is predictive of obesity: the right bacteria can help keep you thin1, 2. Thus, it is important to have a source of good microbes in your diet, like yogurt or kombucha (a fermented tea drink rich in microbes), especially if you’re engaging in activities that tend to kill off these organisms, like drinking heavily or taking antibiotics which don’t discriminate between the good & the bad bacteria.
While drugs may not be able to discriminate between good and bad bacteria, our bodies must be able to in order to maintain intestinal homeostasis; how this happens has been unclear, to-date. However, new research demonstrates how one type of “bad bacteria” – the so called gram-negative strains – are selectively targeted by the body’s immune system3. These microbes present an excess of a type of molecule on their membranes (peptidoglycans) which the body recognizes. The detection of these molecules causes the body to generate lymphatic tissue that specifically targets these bacteria.
As we come to understand more and more about the relationship between gut flora and health in general, this type of research will prove invaluable because it facilitates our understanding of the body’s innate ability to regulate the subset of flora residing within. In other words, there is surely a gradient of immune system function such that some individuals are better able to select which flora to keep and which to oust; understanding how the body achieves this feat will thus widen the scope of western medicine.
1. Turnbaugh PJ, Ley RE, Mahowald MA, Magrini V, Mardis ER, Gordon JI. An obesity-associated gut microbiome with increased capacity for energy harvest. Nature 444: 1027-1031, 2006.
2. Ley RE, Turnbaugh PJ, Klein S, Gordon JI. Microbial ecology: human gut microbes associated with obesity. Nature 444(7122):1022-1023, 2006.
3. Bouskra D, Brézillon C, Bérard M, Werts C, Varona R, Boneca IG, Eberl G. Lymphoid tissue genesis induced by commensals through NOD1 regulates intestinal homeostasis. Nature 456: 507-510, 2008.