Nature's Genius  Using molecules to make the world a better place |
by Sharon J. Proctor The headlines tell us we have some
critical problems to solve – pollution, overpopulation, nuclear proliferation,
climate change, and habitat destruction, to name a few.
When Plettner was a post-doctoral student in Toronto, she explored new industrial uses for subtilisin. Today you’ll find a modified bacterial subtilisin in many clothes detergents, where it dissolves protein stains. One of Plettner’s current research interests at sfu is an enzyme produced by certain bacteria that live in the soil. We’ll call it p450 (it’s actually cytochrome p450 camphor hydroxylase). Certain trees secrete toxic camphor into the soil as a defence against pests, and the bacteria fight back by producing p450, which makes the camphor soluble and non-toxic. Interestingly, we human beings also produce p450. In us its role is to break down noxious foreign substances that enter our bodies (drugs and smoke for instance). It makes those substances water soluble so we can excrete them. (That’s why we must take our antibiotics every few hours.) Plettner and her team are studying how p450 works. “We need to understand the mechanism and determine what products it produces in different chemical situations before we can develop synthetic applications,” she explains. Her group is also exploring some biological alternatives to insecticides. One focus is the gypsy moth. This Eurasian species was accidentally brought to North America in the 1860s and is now a serious forest pest. Gypsy moths eat leaves, stripping deciduous trees bare and killing them. In its life cycle, the female moth releases a chemical called a “pheromone” into the air to attract males. One way to prevent gypsy moth infestations, so the thinking goes, is to interfere with the male’s ability to recognize the female pheromone and thus prevent mating. The sfu team is studying proteins in the male moth’s antennae that bind to the airborne female pheromone molecules and carry them to a sensory nerve. Once they know the binding mechanism, the researchers can design a pheromone mimic that interferes with recognition. Plettner’s group is also studying a honeybee pheromone. It’s a “social” pheromone, called “ethyl oleate.” It controls how honeybees distribute the workload in the hive. “They are even more social than we are,” notes Plettner. “In our society, division of labour is based on career specializations; it’s the same with honeybees. But unlike us, bees divide up the jobs along reproductive lines. Only the queen reproduces. The rest do non-reproductive work, and that work is divided according to age. The oldest bees have the riskiest jobs. They fly away from the safety of the hive in search of nectar. The next oldest bees work at the outer fringes of the hive, and so on down to the youngest, who work at the centre.” What intrigues Plettner is that the oldest bees secrete ethyl oleate in order to inhibit the behavioural development of younger bees. It keeps the latter from advancing up the bee “career ladder,” so to speak. Should the old workers get killed in a storm, however, there’s no one to produce the pheromone. Thus, the next-oldest group quickly matures to replace the missing workforce. And each level below moves up a notch to fill the fresh void. Soon the new “old bees” secrete the inhibiting hormone, and a new generation appears at the bottom. Stability is restored to the hive. Okay, honeybees are interesting. So what! “Human societies also suffer disasters, where a whole generation is lost,” says Plettner. “In parts of Africa, for instance, malaria and aids have incapacitated a huge part of the workforce. Grandmothers now are rearing children. In our own society, older workers retire and younger ones move up the ladder. While our work decisions are not determined by chemical messages (pheromones), they are guided by verbal messages on job openings or new career niches. A honeybee society can be a useful scientific tool for studying what happens when a self-regulating society has to deal with a disaster. The question is, How serious must the disaster be to get a void filled? How much leeway is there? With honeybee data, we can create a mathematical model for bee disaster situations that will help us understand human disaster situations.” Do human beings have pheromones? Not much is known yet. There may be some mother-child bonding substances, but that seems to be all. As for other mammals, pheromones that influence behaviour have so far been identified in rats, mice, and Asian elephants.
When she is not pursuing molecular tools for solving modern problems, Erika Plettner sings. Would you believe it? sfu’s chemistry department has a small choir, Chemsemble. It meets once a week during lunch hour and sings in care homes and community centres. “I sing in Chemsemble as well as in the Capilano College Festival Chorus and the Cecilia Ensemble (an all-women choir, also based at Capilano College). Obviously Plettner is helping make our world a better place in more ways than one. aq
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