Bugs: Coming soon in an ice-cream near you!

'Nanners and Rummy Raisin
Ice Cream"' by ulterior epicure
under a CC license

Within a few days after our birth our intestines get populated by numerous bacteria. Such bacteria will, normally, keep us company until the end of our lives. With them, we are connected by a bit more than a mere co-existence. Current knowledge describes our relationship with plenty of the gut flora microorganisms as "symbiotic": we feed them, provide warmth and shelter to them and in return the keep our guts safe from pathogens, train our immune systems and release metabolites of theirs, some of which are necessary for us. Well, that relationship does go pear-shaped occasionally, but life is full of messy stuff, isn't it?

The interesting thing is that the more we look into our intestinal population the more links we find between their existence and our lives. Yesterday, the New Scientist was highlighting research findings on rats, which suggest that the composition of the gut flora has an effect on appetite, initially, and, later on, changes in the body weight: Changing the gut flora of obesity-resistant rats to that of the obesity-inclined one increased the appetite, firstly, and the weight, secondly, of the former.

Weight changes and the composition of the gut flora is nothing new. In 2006, the New Scientist featured a corresponding article. It was based again on research carried out on mice. That time they compared normal μmice with ones that had been living in sterile conditions and, thus, had no microorganisms within their digestive track. Those mice tended to stay slim. Having their gut populated by the flora of the normal mice lead to a body weight increase of about 25%. If the flora used was similar to that of obese mice, the weight gain was much higher. That observation was attributed to the effect of the gut flora on the food that passes via the intestines; the microorganisms living there help metabolize it more efficiently, thus producing more energy the mass unit than without their intervention. The more efficient the microorganisms are, the higher the weight gain for mice.

Combining the two observations there are several questions that come to mind:

• Let's assume that gut flora that is more efficient in processing the food we normally eat leads to us getting more calories out the food. Temporarily, that will lead to weight increase unless we either reduce our food intake or increase our physical activity. However, it is suggested in the 2012 article that the appetite (of rats) is enhanced. Does this mean that the flora microorganisms mess with the energy intake - appetite mechanism of the host? And if yes, is that a temporary effect? What pathway does it messes up with?
• Since the gut flora lives on what food we consume and on the metabolites secreted by our cells, locally, do they have any mechanism to "encourage" us to eat the food that is most nutritious to them? I don't necessarily refer to "mind-control" but to any pleasant or unpleasant symptom that may encourage or discourage us from eating stuff that "tastes" nice or not-so nice, respectively, to our intestinal guests.
• Is it possible to sustainably change one's gut flora in such a way that it will lead to better weight control? Can this be done in a safe way? What will be the catches (because, surely, there will be at least one downside!)?

The last point carries particular weight for the food industry. Foodstuffs with probiotic content have been consumed practically since the beginning of civilisation; fermented dairy products being a common example. Recently, the trend has expanded and, for some time, probiotics (and prebiotics) became central to what is typically referred to as "functional food".

'Strawberry Panna Cotta'
by Matthew S. Cain under
a CC license

If probiotic microorganisms can indeed help maintain a healthy body weight, without negative side effects, they could become particularly interesting for foods that tend to be tempting and are often responsible for making a weight-loss diet feel particularly punishing.

Ice-cream is a good example. The idea has been explored a few years ago and there seems to be little concern for technological limitations. Household-oriented recipes have also been available for - say - yoghurt ice-cream or more exotic stuff, such as kefir-based chocolate ice-cream.

Having said that, I find the path of "slimming" foods to be a potentially slippery one. Regardless of how pleasant the thought is of devouring tons of yummy ice-cream and, still, lose weight, the wise thing to do is seek for a healthy, balanced diet and live a life with plenty of physical activity. And then, why not, enjoy the occasional scoop or two of our favourite dairy vice....

Mind control... the natural way...

'Zombie walk 2010'
by rodolpho.reis
under a CC license

A few weeks ago, the story of the 'ability' of some humble members of the lactobacillus genus to alter the behaviour of mice made headlines in many online media and gained several minutes of publicity on the TV.

The story was based on a paper of Cryan et al. in PNAS, which describes the effect on the behaviour of mice when fed with feed supplemented with Lactobacillus rhamnosus; altogether, mice became more relaxed. Although that's not the first time that gut bacteria have been shown to have an effect on the mood of mice in vivo, this time the impact to the public seems to be higher.

Symbiotic relationships in living organisms is nothing too uncommon. That applies to both mutualistic and parasitic symbiosis. Although 'mind control' cases have been known, especially in parasitic symbiosis, it wouldn't have been easy for me to imagine that the same would apply to a mutualistic symbiosis, especially if that was taking place in the gut.

The 'mind control' cases one would imagine that they should involve an organism with direct access to the brain or, at least, to the bloodstream. The infection of the bullet ants from cordyceps is an example. The fungus forces the infected ant to climb upwards and firmly grab itself. There, the ant will eventually die and the ascocarp (the fruiting body of the fungus) will come out of the ant's head.



'Mind control' can be used by insects which want to lay their eggs on their ideal host, too. For the orb spider, for instance, the nemesis is the pompilid wasp, which temporarily immobilises the spider, lays an egg on it and let the larva do the rest. The larva sucks nutrients from the spider and, when the time comes, chemically instructs the spider to alter its web in such a way that it can support the cocoon that the larva will later on make for itself. Needless to say that the orb spider doesn't survive the process and becomes dinner, after all. (the video below shows the process - the action starts from about 03:00)



An even spookier approach is practiced by the Ampulex compressa wasp. That uses cockroaches to lay its eggs onto. To manipulate the cockroach, the wasp injects, in series, firstly a temporary numbing agent in the cockroach's brain and, then, a chemical that blocks its escape reflex. After the process, the cockroach is alive and well (not for too long though) and follows the wasp's will. The end is bitter in this case, too, as the larvae will consume the cockroach in the process, starting from its non-vital organs.

Snails, too, can host parasites. (I found a link to the video below at http://primesurrealestate.com/2010/04/mind-altering-parasites/).



For humans, the list of parasites is not too short, either. But I am not aware of any zombie-like mind control bugs. Yes, toxoplasma gondii can alter the behaviour and behavioural characteristics of people, affecting males and females in different ways but not in the grotesque way that bullet ants are controlled by the fungus. Still though, the effect from toxoplasma might be responsible for the macroscopic properties of societies around the world, taking into consideration how widespread toxoplasmosis is, although other factors are likely to exercise far higher influence (http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1635495/).

A number of diseases are also known to affect the mental processes, usually messing with the brain tissue (e.g., Alzheimer's, syphilis, etc.) but such changes - I suppose - are non-reversible.

Going back to the story with the mice and lactobacillus rahmnosus, the beauty in it is that the effect is 'subtle'. Measurable and real but mild and reversible. And that shows a lot of potential to be explored on the use of probiotics not only for the protection of the gut's normal function but also for the delivery of 'brain-related' interventions. What makes things even more interesting is that living bacteria are adaptable and 'intelligent' in the sense that they may be able to perform their 'mind-controlling action' (e.g., excreting a cocktail of chemicals) only under the right conditions. Just imagine mitigating the stress feeling by adopting a diet rich in probiotics - e.g., within fermented food - with the ability to respond to in-gut stress markers. It is so much easier than having to take pills and the fact that their action is subtle may allow individuals to also train themselves to feel less stressed.

It seems, after all, that diet does have the potential for an even greater impact on our lives...