Buried in the sand, the only visible part of the fish-hunting cone snail is its brightly colored siphon, waving alluringly in the water. The cone snail's prey, a large clown fish swimming by, takes the bait as the cone snail’s venomous harpoon tooth launches into the fish, paralyzing it immediately, allowing the snail to swallow the helpless fish whole. α-conotoxin, one small part of the cone snail's venom, is currently being tested as an alternative to morphine for use during surgery. Another cone snail venom component that sedates fish is currently in clinical trials for epilepsy.
I have shown this video, included in Exploring Biodiversity: The Search for New Medicines, to several of my introductory biology classes, as illustration of the importance of preserving biodiversity. My students were thoroughly engrossed and amazed to hear that the cone snail, a slow-moving critter, is actually a predator equivalent to a shark. For all of these info-bits and equally great content about drug discovery, I highly recommend the inclusion of this entertaining and informative DVD set as part of a K-12 or college introductory biology curriculum.
Disk 1 contains four fascinating, hour-long lectures on biodiversity that were delivered to an audience of high school students, two each by Professors Baldomero Olivera (University of Utah) and Bonnie Bassler (Princeton University). The DVD also provides separate menu access to "chapters" from the lectures and to animations and videos excerpted from the lecture presentations. Besides the four lectures, Disk 1 includes two brief introductory talks : E.O. Wilson on biodiversity and Eric Chivian on the importance of biodiversity to human health and the development of new medicines. Disk 2 includes interviews with the two speakers, profiles of young scientists, a Nova episode on Bassler, an HHMI Interactive exercise on sorting seashells, segments on quorum sensing and bioluminescence in bacteria, and discussions with lecturers and graduate students.
In his introductory remarks, Wilson defines the biosphere as "a thin, membrane-like layer plastered on the surface of the planet, so thin you can't see it edgewise from an orbiting shuttle, on which all the world's species inhabit." Wilson informs his audience that, due to the accelerated rate of the disappearance of biodiversity, "Species are becoming extinct before we even know they exist." Wilson exhorts young scientists: "Discover new species" (Wilson himself has discovered 400 species of ant). Wilson's law: If you save the living environment, the biodiversity of the world, you will automatically save the physical environment; in order to save one you have to save the other. He cautions his young audience that if they only focus their efforts on saving the physical environment, they will ultimately lose them both.
Chivian emphasizes the extent to which human health depends on "the healthy functioning of natural ecosystems," warning that we have "no choice but to protect living world." As an example of our reliance on endangered species for potential solutions to major public health problems, he offers the polar bear, which may become extinct in the wild before the end of the century. Global warming and the melting of the Arctic ice sheets are depriving the polar bear of seals, its food source. If polar bears become extinct, Chivian informs us, we lose the possibility of curing osteoporosis, an enormous public health problem, and the cause of 70,000 deaths a year. Hibernating bears, which are immobile for from five to seven months, don't suffer from osteoporosis like humans, who, when bedridden for five months, lose one third of our bone mass due to osteoporosis. Substances in polar bears’ blood could potentially be used to prevent osteoporosis. Polar bears also become obese prior to hibernation but don't experience Type 2 diabetes, another enormous medical problem responsible for a quarter of a million deaths each year.
In his two lectures, Olivera explains the biological purposes of venoms in nature: competition for mates, capturing prey, and self-defense. He describes various venomous snakes, bees, scorpions, spiders, and his lab's pet organism, the cone snail, a predator comparable to the shark. In the video, a buried cone snail, its chemosensory apparatus smelling a nearby fish, averts its proboscis, stabbing the fish, and a harpoon-like tooth (which the snail uses only once) injects paralytic venom into the fish. (Olivera's analogy is to a disposable hypodermic drug-delivery system, evolved by the cone snail 55 million years ago.)
Bassler, a humorous and dynamic speaker, advocates for the misunderstood bacteria. She feels that just because "we don't see microbes, we don't think they are important." In fact, she informs us, humans are made of more bacterial cells than human cells; we are therefore only 10% human and 90% bacteria.
Her research uses the fact that bacteria supply many functions that other organisms lack. She describes the synergism between the nocturnal Hawaiian bobtail squid and vibrio fisherae bacteria: the squid sleeps all day and the bacteria, which live in the squid's light organ, provide illumination at night to protect it from predators. The squid feeds the bacteria and, since the squid has no genes to make light, the bacteria's bio-luminescence genes produce the proteins to make the squid invisible. This is interesting in itself (she shows glow-in-the-dark bacteria), but Bassler's research group has also investigated why the bioluminescence only appears at night. It turns out that during the day, when the bacteria are dilute, there is no bioluminescence, but at night, when they have reproduced and increased in number, bioluminescent proteins are produced.
She has also discovered the informational molecule, a chemical signal sent out by bacteria, called the "auto-inducer," that is used by some pathogenic bacteria, including P. aerogenosa, which kills people with cystic fibrosis. Bassler's research group is developing therapeutics to block what she calls "quorum sensing" to fool bacteria into thinking that they are alone instead of in a group. This type of research can potentially develop cures for Lyme disease, cholera, food poisoning, and ulcers.
Bassler's advice to her young audience is, "If you are curious about the natural world, find a critter you like and study it. If you can find the secret that nature has given it, there is a chance that it will be useful for many things."
This DVD should inspire future scientists, conservation biologists, medical students and nonmajors who are curious about the natural world and human health. The chapters can be accessed separately from the lectures, as can the animations. The supplementary materials included in the DVD are useful, but not essential. A teacher or professor also can develop group exercises or Internet activities as further investigation. HHMI maintains a website accessible through the HHMI website called "Cool Science", and there are other activities at HHMI's BioInteractive website. It is possible to follow up the DVD with laboratory exercises in which bio-luminescence is demonstrated for, or by, the students.
I recommend this DVD set to high school biology and chemistry honors, AP Biology and AP Chemistry and Biochemistry classes and Community College chemistry, biology and biochemistry classes. I think that students will find the lectures, associated materials and exercises fascinating in their revelation of the importance of biodiversity to human health and will learn from the lecturers’ easy to understand, not-extremely technical presentations of forefront research in disease prevention.