Thursday, November 13, 2014

The history of _Herpetomonas megaseliae_ and the bracelet

The history of Herpetomonas megaseliae:

Herpetomonas megaseliae is a single-celled animal that lives naturally inside a tiny fly named Megaselia scalaris. In order to understand why H. megaseliae is so interesting, you have to appreciate the fly, M. scalaris. This fly is one of the truly obnoxious survivors, and so, it turns out, is the parasite H. megaseliae that lives inside it. Megaselia scalaris lays its eggs in about any kind of organic material from the rankest of garbage to the cleanest of sterile culture media, but generally it prefers the rank garbage, or better yet, sewage-soaked soil and even feces. Rotten fish that have been stored in formaldehyde are pretty attractive to this fly. So anything that might have been thrown away, from bacterial Petri plates to toad manure, is a magnet for M. scalaris. This wide range of larval substrates is the reason why M. scalaris is such a survivor; it can get by on all kinds of things other flies treat as garbage. Quite literally, M. sclaris has the ability to fall into a pile of shit and come out smelling like a . . . . well, about like a very healthy fly. Thus we have our basic metaphor: survivors are not very picky, regardless of the organisms playing this role.
Among the most remarkable demonstration of this survivorship ability involved a very large and beautiful lizard, Basiliscus plumifrons, that we had in the lab many years ago as part of a study of the biogeography of parasites that infect reptiles. This lizard had food and water dishes in its aquarium; the food was mainly meal worms and crickets, although once in a while it would get a roach. A dish full of meal worms was also attractive to Megaselia scalaris, and before long there were fly larvae crawling around in the litter and food dish. Naturally, B. plumifrons ate these fly larvae (it would also try to eat your hand if you didn’t handle it carefully.) But the fly larvae then ate their way out of the lizard’s stomach and through the skin, leaving tiny holes. The lizard eventually died and we didn’t figure out why until a grad student cultured a piece of muscle and discovered Herpetemonas megaseliae, a parasite that could only have come from the fly larvae. The lizard and formaldehyde fish provide a rather sobering lesson: environments intended to kill things can turn out to be breeding grounds for survivors.
Herpetomonas megaseliae is a member of the same family as numerous other parasites that cause untold misery and enormous economic loss around the world. Some of the diseases caused by these parasites include classical African sleeping sickness, nagana—the livestock disease that prevents cattle from being raised profitably over a 4 million square mile region of Africa, leishmaniasis (sometimes horribly disfiguring), and Chagas’ Disease, a devastating illness that occurs throughout much of Latin America and which, according to data provided by molecular biologists, has occurred there for thousands of years. So regardless of its fondness for garbage, H. megaseliae is a member of a distinguished group of organisms.
Most of H. megaseliae’s relatives can be cultured, but they are fastidious pansies that must have rich, sterile, usually blood-based environments, and the correct temperatures. Herpetomonas megaseliae, however, can grow in a lot of different environments. One of its favorites at the time was called LPG, which stands for Locke’s balanced salt solution (L) plus (P) Guinea pig shit (G). It also grew at relatively high temperatures that would kill its pansy-ass relatives (“If you can’t stand the heat, get out of the kitchen.”) Most of the world’s scientists and doctors, especially those in armies, think that the pansy-ass relatives are very important. If H. megaseliae could talk, it would probably agree with the doctors. But among its kin, H. megaseliae is, like its fly host, a survivor. Furthermore, it was quite cooperative, being easily manipulated to develop into particular life cycle stages on a human schedule, so that a person could do a set of experiments in the morning and be on the golf course by mid-afternoon.
When my students and I first decided to study H. megaseliae, back in the late 1960s or early 1970s, that decision was based on our sense that this parasite was simply a very interesting animal. As we studied it for years, we realized that not only was it interesting from a biologist’s perspective, but it was also interesting metaphorically because of its survivorship qualities and its ability to perform under the most trying of culture circumstances. All of the students who were attracted to H. megaseliae seemed to be people who could, or would, do things that other students couldn’t, or wouldn’t, do, and furthermore, those things seemed to advance the careers of people who could, or would, do them. If you’re in academia, you know what those “things” are and how such activities produce transferable skills by default.
About this time in my career I was walking through a mall in Lincoln, NE, where a bunch of artists had set up exhibits. One of these artists was making jewelry, and just on a whim I asked her if she could make a bracelet with H. megaseliae on it. She said it would be easy, so I drew her a picture, and a week or later I picked up this bracelet. People, especially my departmental colleagues at UNL, probably thought I was a jewelry jerk for having this bracelet made, and then wearing it, but it was actually my statement that I thought the students in my lab who could do anything under trying conditions were more admirable role models for the next generation of young scientists than were my pansy-ass colleagues. I’ve worn that bracelet now, pretty much every day, for the past 40+ years.


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