Our Microbiome May Be Looking Out for Itself

August 18, 2014 4:48 AM

Your body is home to about 100 trillion bacteria and other microbes, collectively known as your microbiome. Naturalists first became aware of our invisible lodgers in the 1600s, but it wasn’t until the past few years that we’ve become really familiar with them. This recent research has given the microbiome a cuddly kind of fame. We’ve come to appreciate how beneficial our microbes are — breaking down our food, fighting off infections and nurturing our immune system. It’s a lovely, invisible garden we should be tending for our own well-being. But in the journal Bioessays, a team of scientists has raised a creepier possibility. Perhaps our menagerie of germs is also influencing our behavior in order to advance its own evolutionary success — giving us cravings for certain foods, for example.

Maybe the microbiome is our puppet master.

Is eating behavior manipulated by the gastrointestinal microbiota? Evolutionary pressures and potential mechanisms BioEssays
Microbes in the gastrointestinal tract are under selective pressure to manipulate host eating behavior to increase their fitness, sometimes at the expense of host fitness. Microbes may do this through two potential strategies: (i) generating cravings for foods that they specialize on or foods that suppress their competitors, or (ii) inducing dysphoria until we eat foods that enhance their fitness. We review several potential mechanisms for microbial control over eating behavior including microbial influence on reward and satiety pathways, production of toxins that alter mood, changes to receptors including taste receptors, and hijacking of the vagus nerve, the neural axis between the gut and the brain. We also review the evidence for alternative explanations for cravings and unhealthy eating behavior. Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating.

Microbial genes, brain & behaviour – epigenetic regulation of the gut–brain axis Genes, Brain and Behavior
To date, there is rapidly increasing evidence for host–microbe interaction at virtually all levels of complexity, ranging from direct cell-to-cell communication to extensive systemic signalling, and involving various organs and organ systems, including the central nervous system. As such, the discovery that differential microbial composition is associated with alterations in behaviour and cognition has significantly contributed to establishing the microbiota–gut–brain axis as an extension of the well-accepted gut–brain axis concept. Many efforts have been focused on delineating a role for this axis in health and disease, ranging from stress-related disorders such as depression, anxiety and irritable bowel syndrome to neurodevelopmental disorders such as autism. There is also a growing appreciation of the role of epigenetic mechanisms in shaping brain and behaviour. However, the role of epigenetics in informing host–microbe interactions has received little attention to date. This is despite the fact that there are many plausible routes of interaction between epigenetic mechanisms and the host-microbiota dialogue. From this new perspective we put forward novel, yet testable, hypotheses. Firstly, we suggest that gut-microbial products can affect chromatin plasticity within their host's brain that in turn leads to changes in neuronal transcription and eventually alters host behaviour. Secondly, we argue that the microbiota is an important mediator of gene-environment interactions. Finally, we reason that the microbiota itself may be viewed as an epigenetic entity. In conclusion, the fields of (neuro)epigenetics and microbiology are converging at many levels and more interdisciplinary studies are necessary to unravel the full range of this interaction.

Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve PNAS
There is increasing, but largely indirect, evidence pointing to an effect of commensal gut microbiota on the central nervous system (CNS). However, it is unknown whether lactic acid bacteria such as Lactobacillus rhamnosus could have a direct effect on neurotransmitter receptors in the CNS in normal, healthy animals. GABA is the main CNS inhibitory neurotransmitter and is significantly involved in regulating many physiological and psychological processes. Alterations in central GABA receptor expression are implicated in the pathogenesis of anxiety and depression, which are highly comorbid with functional bowel disorders. In this work, we show that chronic treatment with L. rhamnosus (JB-1) induced region-dependent alterations in GABAB1b mRNA in the brain with increases in cortical regions (cingulate and prelimbic) and concomitant reductions in expression in the hippocampus, amygdala, and locus coeruleus, in comparison with control-fed mice. In addition, L. rhamnosus (JB-1) reduced GABAAα2 mRNA expression in the prefrontal cortex and amygdala, but increased GABAAα2 in the hippocampus. Importantly, L. rhamnosus (JB-1) reduced stress-induced corticosterone and anxiety- and depression-related behavior. Moreover, the neurochemical and behavioral effects were not found in vagotomized mice, identifying the vagus as a major modulatory constitutive communication pathway between the bacteria exposed to the gut and the brain. Together, these findings highlight the important role of bacteria in the bidirectional communication of the gut–brain axis and suggest that certain organisms may prove to be useful therapeutic adjuncts in stress-related disorders such as anxiety and depression.

The adoptive transfer of behavioral phenotype via the intestinal microbiota: experimental evidence and clinical implications Current Opinion in Microbiology
Intestinal commensal bacteria or their products may be used to treat CNS disorders.
There is growing interest in the ability of the intestinal microbiome to influence host function within and beyond the gastrointestinal tract. Here we review evidence of microbiome–brain interactions in mice and focus on the ability to transfer behavioral traits between mouse strains using fecal microbiota transplantation (FMT). Transplantation alters brain chemistry and behavior in recipient ex-germ free mice, raising the possibility of using FMT for disorders of the central nervous system, and prompting caution in the selection of FMT donors for conditions that may include refractory Clostridium difficile infection, diabetes and inflammatory bowel disease in humans.

•Behavioral phenotype can be transferred via the intestinal microbiota in mice.
•Changes in behavior in recipient mice are accompanied by changes in brain chemistry.
•Investigation of the intestinal microbiome in central nervous system (CNS) disorders is warranted.
•Donor screening for fecal transplants should exclude CNS and psychiatric illness.

The potential for Microbial Psychiatry previously

posted by Blasdelb (56 comments total)

Not really clear on why that is creepier than the reptilian sections of your brain developing tastes and urges tailored to benefit some ancestor you've never seen and are only aware of from whatever biology you understand.
posted by LogicalDash at 5:08 AM on August 18, 2014 [16 favorites]

Colbert was right!
posted by Mogur at 5:09 AM on August 18, 2014 [1 favorite]

Not really clear on why that is creepier than the reptilian sections of your brain developing tastes and urges tailored to benefit some ancestor you've never seen and are only aware of from whatever biology you understand.

'Cause germs, ewww
posted by Brandon Blatcher at 5:15 AM on August 18, 2014 [2 favorites]

Or, maybe, drawing a sharp line around our "selves" is as impossible and impractical as other kinds of sharp distinctions. If the bacteria inside us have always influenced us, how are they not part of the complex set of interactions that create us in each moment?

In the interests of full disclosure, I welcomed the rule of my innerlords a long time ago. Hail the new old flesh!
posted by GenjiandProust at 5:17 AM on August 18, 2014 [14 favorites]

I think this is going to make it easier for me to fight cravings for shortbread and muffins. Its like I'm fighting against the will of an occupying army.
posted by Slackermagee at 5:17 AM on August 18, 2014 [21 favorites]

And all this time I've been blaming my parents for my problems instead of my fat, anxious bacteria! Bring on the vanco!
posted by mittens at 5:24 AM on August 18, 2014 [6 favorites]

I would like to take this opportunity to thank both the chocolate and the beer germs for their continued support.
posted by Thorzdad at 5:28 AM on August 18, 2014 [39 favorites]

This is really only a distinction if you believe in free will.
posted by shakespeherian at 5:35 AM on August 18, 2014 [5 favorites]

"During fetal development, one part turns into your central nervous system while the other develops into your enteric nervous system. These two systems are connected via the vagus nerve, the tenth cranial nerve that runs from your brain stem down to your abdomen. This is what connects your two brains together, and explains such phenomena as getting butterflies in your stomach when you're nervous, for example."
posted by dragonsi55 at 5:36 AM on August 18, 2014 [9 favorites]

[more inside]
posted by Curious Artificer at 5:39 AM on August 18, 2014 [54 favorites]

As a layperson I'm glad that links such as this are clearly written so that I can get the broad implications.

I'm impatient to see treatment methodologies come from bettering our understanding of our interdependence, but greater knowledge of our mutual interdependence should make us even more cautious about the little bitty "others" we may tread upon.
posted by mightshould at 5:46 AM on August 18, 2014

I think this is going to make it easier for me to fight cravings for shortbread and muffins. Its like I'm fighting against the will of an occupying army.

What if this is just what they want you to think?
posted by GenjiandProust at 5:46 AM on August 18, 2014 [3 favorites]

Then my lord is wise and kind.
posted by mr. digits at 5:52 AM on August 18, 2014 [1 favorite]

I think Bill Bryson summed it up appropriately: it's Bacteria's world. We just live in it.
posted by dry white toast at 5:53 AM on August 18, 2014 [2 favorites]

[cue ominous Godspeed You! Black Emperor drone] We are trapped in the belly of this horrible machine, and the machine demands shortbread and muffins, damn your eyes.
posted by Ryvar at 5:55 AM on August 18, 2014 [5 favorites]

"I'm impatient to see treatment methodologies come from bettering our understanding of our interdependence, but greater knowled ge of our mutual interdependence should make us even more cautious about the little bitty "others" we may tread upon."

There is a lot of crazy and woo around all of this, like how the modern anti-vaxx movement is built around Wakefield's clearly fraudulent connection between the gut and the MMR vaccine, as well as various diets that all lack clear evidence. However, as this shows, the basic idea that some neurological disorders can be positively or negatively affected by the microbial composition of the gut has been very plausible for a while - even if there is no clear evidence pointing to any particular neurological disorder being affected this way, or microbial composition that can have such an effect, or treatment that can cause that composition. The effects of something like that being found are kind of fun to think about though, psychiatric facilities would need to get a lot more particular about poop, the ethics and logistics of fecal transplants for both C. difficile problems and psychiatric/neurological disorders would get really weird really fast, and "splashback" would turn into a simultaneously dead serious, disorienting, and hilarious epidemiological concern.

I hope the subject will be a lot more clear over the next year or two, Behavioral/neurological microbiology was beginning to be a thing back in the '90s before it kind of fizzled out with a lack of results that could be described as both exciting and solid, at least beyond a few clearly demonstrated but very narrow conclusions - like how you can treat some brain disorders in mice with antibiotics in ways that don't make sense otherwise. What is exciting is the ability of papers like this one to use the modern sequencing techniques that have pretty clearly demonstrated how linked microbiota is to obesity in the last couple of years, as well as Chrons disease just recently, the radical clarity of which I think the Zimmer undersells.
posted by Blasdelb at 5:56 AM on August 18, 2014 [7 favorites]

MegaPost of Parasites that turn their hosts into zombies Previously
posted by Blasdelb at 5:57 AM on August 18, 2014 [4 favorites]

Because microbiota are easily manipulatable by prebiotics, probiotics, antibiotics, fecal transplants, and dietary changes, altering our microbiota offers a tractable approach to otherwise intractable problems of obesity and unhealthy eating.

So the new and easier way to deal with intractable problems of obesity and unhealthy eating may involve dietary change? Hmm.
posted by Segundus at 5:57 AM on August 18, 2014 [1 favorite]

So the new and easier way to deal with intractable problems of obesity and unhealthy eating may involve dietary change? Hmm.

Maybe with less shitty judging and haha fat people!

Nah, who wants to stop shitty judging and haha fat people, amirite?
posted by winna at 6:01 AM on August 18, 2014 [9 favorites]

I would like to take this opportunity to thank both the chocolate and the beer germs for their continued support.
posted by octobersurprise at 6:03 AM on August 18, 2014

"So the new and easier way to deal with intractable problems of obesity and unhealthy eating may involve dietary change? Hmm."

While I get the appeal of reasoning that you has been right about whatever all along, our models for understanding obesity, much less its relationship to diet or the food choices that create diets, remain wildly inadequate to the task of effectively treating it.
posted by Blasdelb at 6:07 AM on August 18, 2014 [5 favorites]

You are what your gut microbes seduce you to eat?
posted by notyou at 6:07 AM on August 18, 2014 [2 favorites]

This is really only a distinction if you believe in free will.

I'd say I do, but then, it's not really my choice, is it.
posted by mrgoat at 6:07 AM on August 18, 2014 [4 favorites]

It this was true, wouldn't we just be eating feces like rabbits?
posted by Renoroc at 6:09 AM on August 18, 2014

I totally dig the way this topic lets me have fun reading something that is intellectually deep and very creepy at the same time. That said, I wish the popular press would stop emphasizing the "OMG, the bacteria are controlling us" meme. It seems quite clear that in many cases the bacteria are making us healthier. For example, in the first NYT link (my emphasis):

Adding certain species of bacteria to a normal mouse’s microbiome can reveal other ways in which they can influence behavior. Some bacteria lower stress levels in the mouse. When scientists sever the nerve relaying signals from the gut to the brain, this stress-reducing effect disappears.

Some experiments suggest that bacteria also can influence the way their hosts eat. Germ-free mice develop more receptors for sweet flavors in their intestines, for example. They also prefer to drink sweeter drinks than normal mice do.

[...]

Research by Dr. Cryan and others suggests that a healthy microbiome helps mammals develop socially. Germ-free mice, for example, tend to avoid contact with other mice.

So, yeah, the microbes "take care of themselves", but in many cases it's "enlightened self interest". Keeping their environment healthy is good for them!
posted by mondo dentro at 6:20 AM on August 18, 2014 [3 favorites]

One of the ways that my 5-year-old is not like me is that upon finding out about the existence of eyelash mites, he demanded to see pictures. I found him a youtube video of all the different mites that live on your skin and hair munching away on dead cells, and while I shuddered and itched, he gasped and said, "Mommy! They are so beautiful!"

Wait until he finds out about his gut bacteria bosses.
posted by Eyebrows McGee at 6:47 AM on August 18, 2014 [21 favorites]

Perhaps it might make us even more cautious about antibiotic use, which would be a generally good thing, I think. It seems like periodically killing off our gut bacteria cannot be a good thing given this relationship.
posted by idb at 6:48 AM on August 18, 2014 [4 favorites]

I love my inner biome and agree with its enlightened decisions of my own free will. And I'm not just programmed to say that.
posted by Naberius at 6:56 AM on August 18, 2014 [4 favorites]

i do know that killing off my gut bacteria with antibiotics caused me to be intolerant of coffee in excess of a cup a day, as per my docs. Come back bacteria, come back!
posted by angrycat at 6:59 AM on August 18, 2014 [2 favorites]

I've been thinking about these possibilities for several years now (and my wife is probably so tired of hearing about it), and I think you can even possibly see the influence of various dominant microbiota in the rise of different civilizations with distinctive cultures (cat worshipping Egyptians and toxoplasmosis anyone?). I agree it's probably not nearly as simple a reality as the scary thought that bacteria are "controlling us" suggests, as in many cases, microbiota are already legitimately part of us in every way that matters and have been here shaping us and being shaped by us all along. But I think there are varying degrees of benevolent and malevolent microbiotic influences at play in our world, and that changes in our microbiomes, invasive biota, etc., can effect large-scale cultural and historical trends. (I've been working on and off on a creative writing project on these very themes.) On one hand, we're sort of like giant biological robots who can be used to perform large-scale physical labor for the benefit of bacterial cultures, but on the other hand, those bacterial cultures are often integral parts of who we are, so it's not simple exploitation, but cooperation. The only catch is, we generally aren't conscious of any of this stuff going on in the background influencing us (that is, we know nothing of the politics of microbiota, so to speak), and some bugs behave malevolently towards us.

Even the nightmare total control scenario still doesn't disprove free will as it in fact just shifts all the agency to the bugs. If hypothetical behavior-controlling bugs can have agency, that would actually be an instance of free will, not a disproof of it.
posted by saulgoodman at 7:04 AM on August 18, 2014 [2 favorites]

So germ-free people are relatively laid-back introverts who prefer savory to sweet?
posted by rue72 at 7:09 AM on August 18, 2014 [3 favorites]

One of the ways that my 5-year-old is not like me is that upon finding out about the existence of eyelash mites, he demanded to see pictures. I found him a youtube video of all the different mites that live on your skin and hair munching away on dead cells, and while I shuddered and itched, he gasped and said, "Mommy! They are so beautiful!"

Were do you think the infamous power of your eyebrows comes from, anyway?
posted by GenjiandProust at 7:26 AM on August 18, 2014 [5 favorites]

Microbial driven improvements remind me of the Futurama episode featuring parasites improving Fry's life. Granted, Futurama goes way above and beyond what the research is hinting at.

On the other hand, it puts the end of The War of the Worlds in a different light.
posted by ZeusHumms at 7:52 AM on August 18, 2014 [3 favorites]

"I am large. I contain multitudes."
posted by five fresh fish at 8:14 AM on August 18, 2014 [8 favorites]

David Brin, More Science: Microbes, Pathogens & Parasites
posted by the man of twists and turns at 8:23 AM on August 18, 2014

Are we cultivating edible and useful plants or are they cultivating us? This teleological conundrum appears wherever agents interact.
posted by Mental Wimp at 8:25 AM on August 18, 2014 [5 favorites]

Random germ on the street: "I don't know what you're talking about."
posted by Sheydem-tants at 8:39 AM on August 18, 2014 [1 favorite]

I wonder if there's a correlation between antibiotic use and obesity, perhaps even in kids.
posted by idb at 8:44 AM on August 18, 2014 [1 favorite]

I should have thought to include this in the FPP,

A new study led by researchers at San Diego State University has found that more than half the world’s population is host to a newly described virus, named crAssphage, which infects one of the most common gut bacterial species, Bacteroides. This bacterium is thought to be connected with obesity, diabetes and other gut-related diseases. (4:45)

A highly abundant bacteriophage discovered in the unknown sequences of human faecal metagenomes
Metagenomics, or sequencing of the genetic material from a complete microbial community, is a promising tool to discover novel microbes and viruses. Viral metagenomes typically contain many unknown sequences. Here we describe the discovery of a previously unidentified bacteriophage present in the majority of published human faecal metagenomes, which we refer to as crAssphage. Its ~97 kbp genome is six times more abundant in publicly available metagenomes than all other known phages together; it comprises up to 90% and 22% of all reads in virus-like particle (VLP)-derived metagenomes and total community metagenomes, respectively; and it totals 1.68% of all human faecal metagenomic sequencing reads in the public databases. The majority of crAssphage-encoded proteins match no known sequences in the database, which is why it was not detected before. Using a new co-occurrence profiling approach, we predict a Bacteroides host for this phage, consistent with Bacteroides-related protein homologues and a unique carbohydrate-binding domain encoded in the phage genome.
posted by Blasdelb at 8:47 AM on August 18, 2014 [2 favorites]

Me and my microbes have an agreement, they keep my immune system running and I keep giving them live fermented foods and dark chocolate. It's win win.
posted by The Whelk at 8:53 AM on August 18, 2014 [2 favorites]

Scientifically speaking, it seems way off base to talk about any one species controlling the other. It seems far more likely that we're talking about a system in which these "sympathetic" and "antagonistic" interactions emerge as a co-adaptive or co-evolutionary response (depending on the time scale). That is, the "control" (such as it is) goes both ways. But then, I would say that, because my microbes thrive with a host who's a system scientist!

This leads to the following question: if people change their mood by exogenous means (say, talking therapy, picking up new hobby, exercising, etc.) can they alter the composition of their microbiome? My hypothesis would be "yes".

On a related tangent: I've noticed in the past year, perhaps because my aging regulatory processes are slipping in efficacy, that taking antibiotics can mess me up for months. So I now am loath to take them. They truly are a blunt instrument. I took a course of antibiotics a year ago for a sinus infection, and had digestive issues including severe reflux for about 8 months after that. The interesting (and distressing) thing about that is the clinicians operate within such a reductionist paradigm that if you follow their advice blindly you can get into a big-pharma feedback loop: I was prescribed proton pump inhibitors, which might cause other problems (like vitamin deficiencies), leading to the "need" for other drugs, and so on. I rejected the knee-jerk Prilosec Rx and just monitored my diet. The problem seems to have largely resolved itself.
posted by mondo dentro at 8:55 AM on August 18, 2014 [3 favorites]

mondo dentro: On a related tangent: I've noticed in the past year, perhaps because my aging regulatory processes are slipping in efficacy, that taking antibiotics can mess me up for months. So I now am loath to take them. They truly are a blunt instrument.

I've had the same bad experience. Local antibiotics have to be the answer in many cases, and I don't know why they're not used more often.

For example, why do I need to send a huge dose of antibiotics through my intestines of which only a tiny amount will reach my hurting tooth? Surely a much better option would be an injection of antibiotics directly into my gums. It's not like the dentist isn't already jabbing needles in there anyway.
posted by clawsoon at 9:07 AM on August 18, 2014 [3 favorites]

Well, I for one, welcome our new innerlords.
posted by srboisvert at 9:26 AM on August 18, 2014 [7 favorites]

There is an analogy I've been thinking about lately.
We are like cities for bacteria. Industrial infrastructure designed to furnish a community of organisms with the energy and resources they need, dispose of their waste, provide them an optimal climate and so on. The simplest multicellular organisms are little more than a gut. Everything else - locomotion, senses, behavior - evolved to more effectively acquire resources for that gut.
This might be stretching an analogy, but this is why I feel that our increasingly complex and interconnected industrial, civil and informational systems are probably already conscious. Conscious at a level that we will never be able to comprehend or communicate with, any more than our microbiome can talk to us.
posted by calmsea at 9:27 AM on August 18, 2014 [1 favorite]

Maybe with less shitty judging...

While I get the appeal of reasoning that you has been right all along...

You're misinterpreting me (I think): I was piqued to see they were implicitly describing diet change as easy. After all, it's sort of the point of their paper that it isn't. They suggest we can control the bugs 'easily' by diet change (among other things - I paused over the idea of fecal transplant being easy too) - but the paper says our diet is controlled by the bugs.
posted by Segundus at 9:31 AM on August 18, 2014

I kind of assumed that if our microbiome affects us, it's likely yo do so in a symbiotically. Encouraging the host to seek more food than is absolutely necessary was advantageous until pretty recently in the Western world, not sure about parts of the world where calories are more scarce. We're an incredibly complex system,so I can see how things could get out of whack, on the large scale or more subtly.

This encouraged me to follow a number of links, and to learn a little more about conscious stimulation of the vagus nerve for relaxation. Great post, blasdelb.
posted by theora55 at 10:56 AM on August 18, 2014

...and it does look like there might be some research on antibiotic use and obesity.
posted by idb at 11:51 AM on August 18, 2014

One of the things that's most interesting to me about the microbiome is its similarity to the current plight of widespread environmental destruction and degradation. Just as we've pushed millions of species towards the brink of extinction with habitat destruction, we've also effectively wiped out the rich diversity that used to exist in our microbiomes whether through the use of antibiotics, or the reshaping of our diet via industrial agriculture and a homogenization of culinary traditions.

Doctors, like zoologists and botanists before them, are scrambling to collect poop from isolated populations of people who've never had access to an antibiotic in order to preserve some of the genetic diversity that took eons to produce.
posted by ghostpony at 12:23 PM on August 18, 2014 [2 favorites]

ghostpony: One of the things that's most interesting to me about the microbiome is its similarity to the current plight of widespread environmental destruction and degradation. Just as we've pushed millions of species towards the brink of extinction with habitat destruction, we've also effectively wiped out the rich diversity that used to exist in our microbiomes whether through the use of antibiotics, or the reshaping of our diet via industrial agriculture and a homogenization of culinary traditions.

It feels like you're attempting to force the paradigms you're accustomed to on the new data. You're just assuming that industrial agriculture and a homogenization of culinary traditions would reduce the 'rich diversity', when I'm willing to posit that the average person has a diet far more complex than their ancestors, which would promote more diversity, at least within the individual. Plus, with the global movement of people, people have an opportunity to acquire strains that they'd never have encountered previously. On the downside, you might have 'invasive species effects' where weedy, oversuccessful bugs wipe out regional diversity.

Basically, I'm trying to say you can't predict the effects that human development has had on the microbiome just because you dislike industrial agriculture and the homogenization of culture. And it's possible for negative 'ecological' effects to occur while human health effects improve (e.g. a loss of diversity across all humanity while the diversity inside individuals increases).
posted by Mitrovarr at 1:45 PM on August 18, 2014 [6 favorites]

Mitrovarr, I shouldn't have couched my comment in the language of environmentalism, nor should I have made assumptions. It didn't add anything to the conversation.

I think what I was trying to get at was the idea that we may be seeing a very contemporary picture of the microbiome in terms of diversity, whether due to changing eating habits or increased usage of antibiotics.
posted by ghostpony at 3:51 PM on August 18, 2014

Antibiotics are routinely given to beef cows because it makes them gain weight faster. Not for any illness, just for weight gain. My readings says this is another cause of antibiotic overuse, creating resistant pathogens.
posted by theora55 at 7:14 PM on August 18, 2014 [2 favorites]

when I'm willing to posit that the average person has a diet far more complex than their ancestors

Wait, is that true? It obviously has to depend on how we're defining ancestors, but it seems like most ancestors of the average person (at least the average American) would have eaten many more animal species than the current person's reliance on chicken and beef, and would've been exposed to more plant species because of seasonality--as opposed to having hundreds of species available all the time, but only eating a couple of them in bulk. Am I thinking of this the wrong way? There would certainly be complexity-limiting bottlenecks...thinking about the Southeastern US diet of a few generations ago which featured pork, corn, and whatever green might be growing, and very little else, but I'm not sure those kinds of situations are representative, are they?
posted by mittens at 4:45 AM on August 19, 2014 [1 favorite]

I woke this morning to find this story in my email about a fungus that turns ants into zombies, getting them to die near the entrance of a colony to ensure the fungus has access to new hosts.
posted by Toekneesan at 4:56 AM on August 19, 2014

Personally, in addition to influencing food based urges, I personally think we will find a huge range of behaviors subject to such influences- the first that comes to my mind is cleaning behaviors because what faster way can microbes proliferate than weakening the host and diminishing cleaning behavior in the home? I would be curious to know what microbes can live both inside and out of the human body which I feel sure someone somewhere has researched but I don't know how to pull up that sort of data.

I wonder if roaches similarly can produce chemicals or specifically carry microbes that damage the health and cleaning abilities of the host, increasing their food supply and likelihood of remaining un-eradicated.

Slime mold controlling a robot.
Slime mold solving a maze.

The videos I've seen of slime mold robots have not focused on input or food sources being accessible to the mold through it's use of the robot, but I imagine that research is being done and that we are vastly underestimating the level of influence such creatures have on our functioning. The ability for a host to identify and fight off pathogenic or parasitic invasions, and also to identify symbiotic and beneficial invasions is something going on in our bodies all the time. Microbes even without entering the brain (and some do just that!) can excrete substances and most certainly if those behaviors increase their access to food or other favorable environmental variables they will learn to do more of that!
posted by xarnop at 9:40 AM on August 19, 2014

Just 5 questions.
posted by 0rison at 3:13 PM on August 20, 2014 [3 favorites]

Holy shit is this an interesting paper,

Commensal bacteria protect against food allergen sensitization PNAS

Abstract
Environmentally induced alterations in the commensal microbiota have been implicated in the increasing prevalence of food allergy. We show here that sensitization to a food allergen is increased in mice that have been treated with antibiotics or are devoid of a commensal microbiota. By selectively colonizing gnotobiotic mice, we demonstrate that the allergy-protective capacity is conferred by a Clostridia-containing microbiota. Microarray analysis of intestinal epithelial cells from gnotobiotic mice revealed a previously unidentified mechanism by which Clostridia regulate innate lymphoid cell function and intestinal epithelial permeability to protect against allergen sensitization. Our findings will inform the development of novel approaches to prevent or treat food allergy based on modulating the composition of the intestinal microbiota.

Significance
The prevalence of food allergy is rising at an alarming rate; the US Centers for Disease Control and Prevention documented an 18% increase among children in the United States between 1997 and 2007. Twenty-first century environmental interventions are implicated by this dramatic generational increase. In this report we examine how alterations in the trillions of commensal bacteria that normally populate the gastrointestinal tract influence allergic responses to food. We identify a bacterial community that protects against sensitization and describe the mechanism by which these bacteria regulate epithelial permeability to food allergens. Our data support the development of novel adjunctive probiotic therapies to potentiate the induction of tolerance to dietary allergens.

posted by Blasdelb at 5:42 AM on August 27, 2014 [2 favorites]