Bacteroides Influence on Host Behavior
Introduction
Bacteria often live in a special mutualism with large multicellular organisms: one such relationship of particular interest is that of the human digestive system and its "gut flora", or the microbial life that colonizes it. It is fairly intuitive that in such a relationship the host will dictate temperature, pH level, substrate availability, and a variety of other environmental factors that will determine what types of bacteria are able to colonize it, how these bacteria will behave, and how successful any given species will be in that environment. What is not always such an intuitive aspect of the host/bacteria relationship is the role that the bacteria may play in the behavior and physiology of the host.
The rise in obesity in the western world over the past several decades has prompted researchers to explore possible explanations for this drastic shift in human physiology. An important determinant of the physiology of an individual is that individual's particular genome; and while this may account for a natural tendency towards weight gain for certain genotypes, the human genome has certainly not undergone a radical transformation since the "obesity epidemic" hit the western world. If we look at what has changed in the past few decades, we see people consuming larger-portioned, higer-calorie diets. But how and why does this shift in diet translate to a shift in body composition? Scientists are now looking at the role of the human body as a host to a plethora of bacteria, in particular, the inhabitants of the human gut—referred to collectively as the microbia. The gut flora engage in a key mutualistic relationship with the host, aiding in digestion. The microbia is composed of approximately 1013 organisms that fall into somewhere between 500 and 1,000 distinct species of bacteria (REF2). Of these bacteria the classes Bacteriodes and Firmicutes make up a substantial portion: over 90% of all gut flora fall into one of the two classes (REF3).
Bacteriodes is a gram-negative, rod-shaped bacteria. It resides in the human/mammalian cecum where it ferments polysaccharides from plant fibers using anaerobic respiration. The substrates catalyzed by bacteroides cannot be broken down by host enzymes, but once fermented by bacteriodes can be used and/or stored as energy by the host. It is estimated that up to 15% of the caloric value humans obtain from food is made available to us by bacteriodes (REF), making it a key player to consider when examining the pathway from diet to physiology. Its vital role in energy processes has prompted researcher to explore the role that bacteroides and other bacteria may be playing in the rise in obesity. More specifically put: perhaps the shift to the modern western diet is manipulated/exploited by our gut flora—resulting in a change in body composition and weight.
Host/Bacteria Relationship
What this Means for Humans
Include some current research in each topic, with at least one figure showing data.
Possible Therapeutic Options
Include some current research in each topic, with at least one figure showing data.
Conclusion
Overall paper length should be 3,000 words, with at least 3 figures.
References
Edited by student of Joan Slonczewski for BIOL 238 Microbiology, 2009, Kenyon College.
