Bleary-eyed and staggering, many of us partake in a morning coffee ritual before mustering the courage to face the daily workload. In addition to psychoactive chemicals (drugs, anyone?), the coffee routine provides structure and emotional support — rumours suggest it may be largely a placebo effect, but I won’t go into that debate. Instead, I have developed a sudden curiosity in how caffeine may affect construction quality: after all, it is common to see construction workers cuddling with cups of coffee on a cold morning. Should we be afraid? Turns out, yes, we should be — if the construction workers in question are amoebae.
The above shell, reminiscent of medieval scale armour, was built by an Assulina species, a member of the Euglyphid clan. Euglyphids are thin-footed(=filose) amoebae notable for their orderly construction and secretion of siliceous scales. To push the construction (or even bricklaying!) analogy a bit further yet, the scales are held together by the cement between them. The shapes and arrangement of scales is characteristic of each species, meaning their formation is strictly regulated and not all that random. As soon as you see something morphologically prominent being not random in biology, your first instinct should be to do drugs. On the cells. This can help reveal some of the cellular components involved in the process, but much more importantly — generates freaks. And if you’re a cell biologist, freaks are fun!
So, back to coffee. *sip* This is what caffeine does to our neat and organised Assulina species:
Oh no, our euglyphid has gone out in public completely disheveled! This is from a study by O. Roger Anderson (who also happens to be the god of forams and radiolarians), where Assulina was treated with 5mM of caffeine (Anderson 1995 J Morphol) — for a comparison, drip coffee typically has 3.5-4mM, from a back of the envelope calculation. The scales become crooked, and you can see pieces of cement (the long gooey stuff) horribly misplaced atop the scales. On top of that, some of the scales end up standing perpendicular to the surface altogether!
The scales are made by a membrane system associated with the Golgi apparatus. Presumably, a template is laid down (I don’t know how in the case of Euglyphids, but coccolithophorids (algae with calcareous scales) use a protein-cellulose structure first), and the containing vesicle can then be seen with silica-depositive vesicles fusing with it. This silica gradually accumulates, and the scale matures. It is then delivered towards the mouth of the cell during cell division, where an entirely new test is constructed from scratch, opposite of the older cell. (I wonder if they can repair the test too…). In short, membrane dynamics and the Golgi are essential for scale formation. On the left are scales made by a healthy amoeba:
In addition to neurology magic (I suck at vertebrate biology, go talk to Scicurious instead), caffeine disrupts the Golgi function and membrane trafficking. In plants, caffeine treatments disrupt the cell plate formation, where cellulose-containing vesicles fuse to form the wall between the cells — this produces some really fun freaks! (don’t water your plants with coffee, by the way). If building things within a cell is so dependent on membrane gymnastics, you can imagine that a membrane-trafficking inhibitor might not be the best friend of quality there. And that is exactly the case on the right of the above image — the vesicles are bloated and disorderly, while their contents fare no better.
In the caffeine-treated euglyphids, the scale vesicle struggles to control the shape of its contents. Scales become thicker, rounder, and marred by an irregular surface — along with some organic gunk on the surface, perhaps the cement. There’s a closeup of the weirdness:
The control of the direction of scales upon deposition is also lost — some are perpendicular, while others are inverted altogether. There is a malfunction in whatever mechanism ensures the vesicles are oriented correctly while releasing their scales into the daughter test. The Golgi apparatus itself develops some impressively large tubules which are invisible in normal cells. These can be seen as regularly packed circles near the nucleus in the picture below:
The follow-up question regards what other psychoactive substances do to the amoeba’s construction capabilities. Out of purely academic interests, for example: THC, psilocybin, LSD and LSA, mescaline, DMT… once again, out of entirely theoretical curiosity. Environment Canada has already explored this topic with spiders, but the research field just BEGS for a greater phylogenetic diversity. Furthermore, perhaps testate amoebae and other protists can be used to explore further psychoactive (and, for actual academic research, cytoactive) chemicals. Here’s a guaranteed fundable grant application waiting to be written, for anyone who’s bored (or eager to rise to the heights of scientific and humanitarian contribution!).
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