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.

Recommended by Forbes
What Will Humans Look Like 100,000 Years From Now?
Is Theoretical Physics A Waste Of Resources?
Comcast BusinessVoice: How To Enhance Customer Service With Network Capabilities

How Much Energy Are You Actually Generating When You Pedal A Stationary Bi... Experts Are Saying You Probably Need A Lot More Sleep Than You Think
MOST POPULAR Photos: MLB valuation 2017
+68,682 VIEWS How United Became The World's Most Hated Airline In One Day
MOST POPULAR Photos: The Richest Person In Every State
MOST POPULAR Stan Lee Introduces Augmented Reality For His Kids Universe

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

Kara Margolis, a pediatric gastroenterologist at New York Presbyterian Hospital and a researcher at Columbia University Medical Center, is among the clinicians today exploring the link between autism and gastrointestinal problems, particularly bacterial
dysbiosis. In this article in the Atlantic, she shares some of her clinical experiences showing how treating some autistic patients' gastrointestinal problems helped alleviate some of their behavioral issues, namely aggression and anxiety. In hindsight,
it is easy to see a link between gut health and the central nervous system (CNS). Serotonin is important for many CNS functions such as "appetite, mood and sleep," and as the article in the Atlantic says, the bulk of serotonin is generated in the gut by
the enteric nervous system.

3. Fecal bacteriotherapy

Fecal Bacteriotherapy: transplanting fecal bacteria from healthy individuals into recipients. Alexander Khoruts at the University of Minnesota Medical Center was among the 1st to use this approach to treat Clostridium difficile infections, which are
otherwise difficult to treat with antibiotics. Subsequently, this treatment showed some promise for neurological diseases such as Parkinson's as well, alluding to the microbiome's influence on neurophysiology.

In animal models:

1. A molecular sensor that allows a gut commensal to control its nutrient foundation in a competitive ecosystem

Lora Hooper, then working in Jeff Gordon's lab, used a mouse model experimentally derived to be completely free of microbiota (germ-free mice; Germ-free animal), incolulated with just one lab bacterial strain, Bacteriodes thetaiotamicron, and in this
Proceedings of the National Academy of Sciences article showed that colonization with this one bacterial species alone was sufficient to induce a physiological remodeling program in the mouse small intestine epithelium. Subsequently, she has published
several other papers exploring host-microbe interactions that influence host physiology and immunity.

2. Microbiota Modulate Behavioral and Physiological Abnormalities Associated with Neurodevelopmental Disorders

Sarkis Mazmanian and colleagues at Caltech recently showed in this article in Cell that changes in gut microbiota influence neurophysiology in mice, changes that appear to recapitulate elements of "Autism Spectrum Disorders".

This question originally appeared on Quora. Ask a question, get a great answer. Learn from experts and access insider knowledge. You can follow Quora on Twitter, Facebook, and Google+. More questions:

Microbiome: What do we know about the function of viruses in the microbiome? Bacteria: What are some of the most interesting bacteria?
Human Behavior: What is the smartest thing you have ever done under pressure?

https://www.forbes.com/sites/quora/2016/09/20/how-much-does-the-bacteria-in-our-bodies-influence-our-behavior/#b8f5eab25ac6

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)