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   The Scientist >> Magazine >> Thought Experiment    
   Who Are We Really?    
   Manipulating the human microbiome has ethical implications.    
      
   By Kieran O'Doherty | March 1, 2012    
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   image: Who Are We Really?    
   BACTERIAL FINGERPRINT: There is the possibility that microbial DNA may contain   
   even more information about a person than does their human DNA.Lucy   
   Reading-Ikkanda    
      
   Bacterial Fingerprint: There is the possibility that microbial DNA may contain   
   even more information about a person than does their human DNA.    
   LUCY READING-IKKANDA    
      
   We are human beings. Normally, one might take this to mean that, at least on a   
   biological level, we are defined by our own genome. But living in and on the   
   human body is an ecosystem of microorganisms that outnumber our own cells by   
   at least a factor of    
   ten. It is estimated that there are 100 times as many microbial genes as human   
   genes associated with our bodies. Taken together, these microbial communities   
   are known as the human microbiome. Recent technological and scientific   
   advances, mainly in the    
   field of metagenomics, are rapidly enriching our knowledge of the genomes and   
   functions of many of these microbial communities.    
      
   The ultimate aim of much of this research is to discover how perturbations of   
   the microbiome might be related to various diseases, including inflammatory   
   bowel disease, asthma, and obesity. Other research is currently investigating   
   the potential role of    
   microbes in anxiety, depression, and autism. These findings have the potential   
   to change the landscape of medicine. And they also have important   
   philosophical and ethical implications.    
      
   A key premise of some microbiome researchers is that the human genome   
   coevolved with the genomes of countless microbial species. If this is the   
   case, it raises deep questions about our understanding of what it really means   
   to be human. Typically, we draw    
   a distinction between environmental and genetic factors in understanding human   
   traits and the development of disease. What precisely is meant by   
   "environmental" varies dramatically across disciplines. Irrespective of how   
   environmental factors are    
   conceptualized in a given study, a common focus is their interaction with   
   stable genetic factors. Traditionally, the microbial communities in and around   
   us would be counted towards the environmental, rather than the genetic side of   
   this equation. Given    
   recent findings from human microbiome research, however, this classification   
   may need to be reconsidered. If the microbiome, on a species level, coevolved   
   with the human genome and, on an individual level, is a unique and enduring   
   component of biological    
   identity, then the microbiome may need to be thought of more as "a part of us"   
   than as a part of the environment.    
      
   Ethics of DNA manipulation    
      
   The human microbiome may need to be thought of more as "a part of us" than as   
   a part of the environment.    
   There are practical ethical implications associated with these somewhat   
   philosophical considerations. Over the past few decades a strong ethical   
   position has emerged regarding manipulation of the human genome. In most   
   jurisdictions it is deemed unethical    
   (and illegal) to alter a human genome in such a way that these changes might   
   be passed on to offspring. There are several arguments supporting this   
   position, an important one being to safeguard the right of the child to an   
   "open future." Because the    
   consequences of even ostensibly benign genetic manipulations cannot be   
   predicted with certainty, it is currently deemed unethical to make choices on   
   behalf of a child as it might lead to permanent changes to its biological   
   identity. This reasoning    
   underlies the prohibition in many countries against manipulation of germ-line   
   DNA. An important question thus arises about how permanent certain changes to   
   the human microbiome might be, especially to the microbiomes of infants and   
   children, and whether    
   such changes could be transmitted to offspring.    
      
   Planning for the future    
      
   We alter the mix of our microbial genomes all the time, through changes in our   
   diet and surroundings and, significantly, every time we take antibiotics. It   
   is currently not known how permanent these and other changes to the microbiome   
   are. Certainly some    
   changes are very transient, with the microbiome eventually returning to a   
   fairly stable state. However, it is unclear just how stable the microbiome   
   really is across a person's lifespan. There seems to be an emerging scientific   
   consensus that there is a    
   critical period in infancy and early childhood during which the microbiome   
   initially develops and gains a certain degree of stability. Neonates emerge   
   from a sterile uterine environment and are immediately colonized by microbes   
   from the baby's    
   environment, beginning with the birth canal or, in the case of cesarean   
   section, the mother's skin, which hosts a significantly different bacterial   
   community. It is thus possible that, starting with the mode of birth, early   
   childhood exposure or lack of    
   exposure to certain microbial communities may have important implications for   
   health and illness later in life. For example, researchers in British Columbia   
   are currently investigating the possible role of early childhood use of   
   antibiotics in later    
   development of asthma.    
      
   More important in the context of ethical considerations is the possibility   
   that if the adult microbiome is indeed relatively stable, then such early   
   childhood manipulations of the microbiome may be used to engineer permanent   
   changes that will be with the    
   child throughout life. There is thus the potential that an infant's microbiome   
   may be "programmable" for optimal health and other traits. For example, might   
   we program a baby's microbiome to decrease chances of becoming obese? Or might   
   we program it such    
   that the person will always have a dislike of alcohol? While such manipulation   
   is likely to be motivated by many good intentions, it does raise the familiar   
   specter of "designer" babies, and the ethical problem of making choices for   
   infants and children    
   that may permanently affect their biological identity.    
      
      
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