From: mjs23x@gmail.com   
      
   How Much Does The Bacteria In Our Bodies Influence Our Behavior?   
      
      
      
   SEP 20, 2016 @ 01:11 PM    
   How Much Does The Bacteria In Our Bodies Influence Our Behavior?   
      
      
   Quora ,   CONTRIBUTOR   
       
      
   Opinions expressed by Forbes Contributors are their own.   
      
   (Photo: GEORGES GOBET/AFP/Getty Images)   
      
   How much does the bacteria colonizing our bodies influence our behavior?   
   originally appeared on Quora: the knowledge sharing network where compelling   
   questions are answered by people with unique insights.   
      
   Answer by Tirumalai Kamala, Immunologist, Ph.D. Mycobacteriology, on Quora:   
      
   In my opinion, this question cannot be adequately addressed without addressing   
   its context. We discovered microorganisms in the context of human diseases   
   (Germ theory of disease) and ever since we have tended to perceive   
   microorganisms as either    
   potentially pathogenic (with respect to humans) or as potentially benign (with   
   respect to saprophytes). This thinking has informed not only the culture of   
   fields such as immunology and medicine but indeed modern culture itself. Even   
   a casual observation    
   of advertisements touting hand washes that can eliminate 99.9% of "germs"   
   suffices to underscore the extent to which we, as a population, have   
   internalized the message that "germs" are bad and need to be eliminated.   
   However, technology today has brought    
   us to a critical juncture where we are being forced to confront this schism in   
   our thinking on microbes, and to try to engage in some serious rethinking on   
   this issue.   
      
   My view is that we (multi-cellular organisms) would not have been able to   
   evolve if we had engaged with our microbial brethren on such strictly   
   adversarial terms. Existing before our arrival on the scene, the latter have   
   inherent advantages over us,    
   namely, shorter generation times and higher rates of mutations. Given such   
   advantages, we (multi-cellular organisms) perforce needed to negotiate and   
   compromise with the microbial world in order to even evolve in the first   
   instance, let alone continue to    
   exist and thrive. Taking such thinking to a logical next step then would be to   
   acknowledge that microbes could potentially influence every aspect of our   
   physiology, including behavior. This is an important consideration because   
   scientific research is not    
   pursued in a vacuum, but rather underlying, often implicit assumptions drive   
   research, and I believe that for far too long an adversarial stance towards   
   microorganisms has dominated thinking in the biomedical field.   
      
   I am not sure that there is one compelling example yet in humans of a   
   particular microorganism influencing behavior in the manner that Toxoplasma   
   gondii infection has been shown to influence the behavior of an infected   
   mouse, but a body of work is being    
   generated that shows that the microbiome shapes not only gut health but also   
   other aspects of our physiology including neurophysiology. I consider what   
   follows to be a short introduction to this topic.   
      
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   To my knowledge, it was the renaissance scientist René Dubos who first showed   
   that merely transferring the intestinal microflora from one mouse strain to   
   another soon after birth was itself sufficient to imprint many characteristics   
   of the former to the    
   latter, characteristics such as growth rate, body weight and resistance to   
   infections, that then stably persisted for the life of the mouse. In fact, as   
   far back as 1960, Dubos generated much compelling evidence through a series of   
   extensive experiments    
   in mice models and concluded that "many characteristics assumed to be inherent   
   in an individual can in reality be determined by the intestinal flora of the   
   intestinal tract." One such example is this paper from 1960: The Effect Of The   
   Intestinal Flora On    
   The Growth Rate Of Mice, And On Their Susceptibility To Experimental   
   Infections.   
      
   A remarkable example of the intertwining between a microorganism and a   
   multicellular organism is that of Vibrio fischerii and the deep-sea squid.   
   Margaret McFall-Ngai of the University of Wisconsin elegantly demonstrated   
   that the light organ (the eye) of    
   the deep-sea squid is actually composed of a symbiotic bacterium, Vibrio   
   fischerii (V. fischerii). In order for the squid to have a functioning light   
   organ, its eye epithelium needs to be colonized at a particular stage in its   
   development by V. fischerii,   
    and only V. fischerii. Such is the exquisite specificity of this partnership   
   that the light organ does not develop if V. fischerii is substituted with   
   another Vibrio species. I recommend watching McFall-Ngai's NIH Director's   
   seminar on Jan 16, 2013, "   
   Living in a Microbial World: Deciphering the Molecular Language of   
   Partnership" where she describes in detail this exquisitely specific   
   dance-like process, and explores at length how the microbiome appears to   
   influence every aspect of our physiology    
   including behavior.   
      
   Today, with the great interest in the human microbiome, witness the NIH funded   
   Human Microbiome Project and others, we are witnessing an explosion of data in   
   the scientific literature rediscovering the seminal findings of René Dubos,   
   namely the profound    
   influence of the microbiome on our normal health and physiology. I mention   
   René Dubos as my attempt to right the oversight that those following in his   
   footsteps have tended to overlook his considerable contribution to this topic.   
      
   A few notable examples of the influence of the microbiome, to add to those   
   mentioned by Daniel Cisalpino:   
      
   In humans:   
      
   1. Microbial ecology: Human gut microbes associated with obesity   
      
   Jeff Gordon and colleagues at Washington University School of Medicine, St   
   Louis, MO, published in Nature one of the 1st populational analyses of human   
   gut microbiome sequencing showing differences in gut microbiota of obese and   
   non-obese individuals.   
      
   2. In Autism, the Importance of the Gut   
      
      
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