Weekend Rebel Science Excursion - 35

Not all messages are well received.

It is Friday again, so let's consider some strange science.

Let's consider how single celled organisms communicate or miscommunicate with each other and with human cells.

And let's consider why they communicate.

The Toxins of Power Blog has featured posts about hermeneutics in the context of microbial communications or lack of communication, as a source for both cognitive success and cognitive dysfunction:

Imagine a graduate student with two thesis advisors. One suggests focusing on the experiments. The other suggests some mathematical modeling. What should the student do? The first strategy might involve doing a little of each, effectively ‘‘averaging’’ their advice. Prioritizing one mentor over the other could be a second option. Finally, when the best choice is unclear, it may be best to flip a coin. Bacteria, which live in complex environments, face similar problems and must respond optimally to multiple conflicting signals.

(Microbial Hermeneutics, emphasis added, cf. 2, 3). Imagine the damage bacteria can do when they receive confusing communication, and therefore do the wrong thing.

The subject of microbial communication is so critical that The Journal of Experimental Biology (JEB) did an issue on it (JEB, January 2013).

One of the papers in that issue informs us that the research into the subject is relatively new:

The ability of parasites to alter the behaviour of their hosts fascinates both scientists and non-scientists alike. One reason that this topic resonates with so many is that it touches on core philosophical issues such as the existence of free will. If the mind is merely a machine, then it can be controlled by any entity that understands the code and has access to the machinery.

This special issue of The Journal of Experimental Biology highlights some of the best-understood examples of parasite-induced changes in host brain and behaviour, encompassing both invertebrate and vertebrate hosts and micro- and macro-parasites. The observation that parasitic infection can modify specific host behaviours is an old one (see Moore, 2002). The general consensus has been that these parasites have evolved the ability to manipulate host behaviour in order to advance their own reproductive success (Moore, 2002). Unfortunately, there has been a lack of information on two key points of this hypothesis. Firstly, it has proved difficult to unequivocally demonstrate that changes in host behaviour benefit the parasite (i.e. enhance parasitic fitness). Secondly, the mechanisms that parasites use to change host behaviour were completely unknown for many years, particularly in the case of vertebrate host systems.

(Neural Parasitology: Parasites Manipulate Host Behaviour, emphasis added). The use of propaganda, by parasitic elements in government, can be analysed as a macrocosm.

That is, human behavioural dynamics and messaging which works like microbial parasite messaging.

The behavioral changes that tiny microbes can bring about through propaganda messaging is nothing short of phenomenal:

Our first example of propaganda usage is about Sacculina, a parasite:

When a female Sacculina is implanted in a male crab it will interfere with the crab's hormonal balance. This sterilizes it and changes the bodily layout of the crab to resemble that of a female crab ... The female Sacculina has even been known to cause the male crabs to perform mating gestures typical of female crabs ... The natural ability of regrowing a severed claw that is commonly used for defense purposes is lost after the infestation of Sacculina. Although all energy otherwise expended on reproduction is directed to the Sacculina, the crab develops a nurturing behavior typical of a female crab... The male Sacculina looks for a female Sacculina adult on the underside ... then implants himself ... and starts fertilizing ... The crab ... then cares for the eggs as if they were its own, having been rendered infertile by the parasite.

(Wikipedia). Can there be any stronger deceit or propaganda than to deceive a male into thinking it is a biologically functioning female, robbing that male of reality?

Let's take a quick look at two other examples, beginning first with the protozoa Toxoplasma gondii:

If you take a lab rat who is 5,000 generations into being a lab rat, since the ancestor actually ran around in the real world, and you put some cat urine in one corner of their cage, they're going to move to the other side. Completely innate, hard-wired reaction to the smell of cats, the cat pheromones. But take a Toxo-infected rodent, and they're no longer afraid of the smell of cats. In fact they become attracted to it. The most damn amazing thing you can ever see, Toxo knows how to make cat urine smell attractive to rats. And rats go and check it out and that rat is now much more likely to wind up in the cat's stomach.

(Hypothesis: Microbes Generate Toxins of Power). The acts of propaganda also take place in order to deceive plant species:

Phytopathogens can manipulate plant hormone signaling to access nutrients and counteract defense responses. Pseudomonas syringae produces coronatine, a toxin that mimics the plant hormone jasmonic acid isoleucine and promotes opening of stomata for bacterial entry, bacterial growth in the apoplast, systemic susceptibility, and disease symptoms. We examined the mechanisms underlying coronatine-mediated virulence and show that coronatine activates three homologous NAC transcription factor (TF) genes, ANAC019, ANAC055, and ANAC072, through direct activity of the TF, MYC2. Genetic characterization of NAC TF mutants demonstrates that these TFs mediate coronatine-induced stomatal reopening and bacterial propagation in both local and systemic tissues by inhibiting the accumulation of the key plant immune signal salicylic acid (SA). These NAC TFs exert this inhibitory effect by repressing ICS1 and activating BSMT1, genes involved in SA biosynthesis and metabolism, respectively. Thus, a signaling cascade by which coronatine confers its multiple virulence activities has been elucidated.

(Cell - Host & Microbe). This is akin to war practices in the days of castles, with draw bridges and moats, in the sense that sometimes enemies would dress up like knights of that castle, then rushing toward the castle would give a secret signal that deceived the guards into lowering the draw bridge, allowing the adversary into the castle to wreak havoc.

(On The Origin of Propaganda, see also 2). We see that communication takes place in both plants and animals via the microbial version of propaganda.

This communication is not limited to internal communication, because plants and animals also receive various communications from the environment, and react as if they understand what is being communicated:

Vegetation around the world is on the move, and climate change is the culprit, according to a new analysis of global vegetation shifts led by a University of California, Berkeley, ecologist in collaboration with researchers from the U.S. Department of Agriculture Forest Service.

In a paper published June 7 in the journal Global Ecology and Biogeography, researchers present evidence that over the past century, vegetation has been gradually moving toward the poles and up mountain slopes, where temperatures are cooler, as well as toward the equator, where rainfall is greater.

(Climate Change Linked to Major Vegetation Shifts Worldwide, emphasis added). This ties in with last Friday's post concerning what plants know.

Some scientists have noticed that some microbes which are pathogenic have changed their behavior from time to time:

Like pretty much all multi-cellular organisms, humans enjoy the benefits of helpful bacteria. (As you may have heard, there are more [bacterial cells] in the human body than [human cells].) These mutualistic microbes live within the body of a larger organism, and, like any good long-term houseguest, help out their hosts, while making a successful life for themselves. It’s a win-win situation for both parties.

Scientists still don’t understand exactly how these relationships began, however. To find out, a team of researchers from the University of California, Riverside, used protein markers to create a detailed phylogenic tree of life for 405 taxa from the Proteobacteria phylum—a diverse group that includes pathogens such as salmonella as well as both mutualistic and free-living species.

Those analyses revealed that mutualism in Proteobacteria independently evolved between 34 to 39 times, the researchers report in the journal Proceedings of the Royal Society B.  The team was a bit surprised to find that this happened so frequently, inferring that evolution apparently views this lifestyle quite favorably.

Their results also show that mutualism most often arises in species that were originally parasites and pathogens.

(Microbial Languages: Rehabilitation of the Unseen -- 2). The new medical practices of communicating with microbes to change them are in the very early stages, but it seems to be a better way than the ongoing antibiotic wars which kill the good along with the bad.

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An index to this video is here.

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