Category Archives: Life Science

Ants Counting Their Step

Most ants get around by leaving smell trails on the forest floor that show other ants how to get home or to food. They squeeze the glands that cover their bodies; those glands release a scent, and the scents in combination create trails the other ants can follow.

That works in the forest, but it doesn’t work in a desert. Deserts are sandy and when the wind blows, smells scatter.
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It’s already known that ants use celestial clues to establish the general direction home, but how do they know exactly the number of steps to take that will lead them right to the entrance of their nest?

Wolf and Whittlinger trained a bunch of ants to walk across a patch of desert to some food. When the ants began eating, the scientists trapped them and divided them into three groups. They left the first group alone. With the second group, they used superglue to attach pre-cut pig bristles to each of their six legs, essentially putting them on stilts.
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The regular ants walked right to the nest and went inside. The ants on stilts walked right past the nest, stopped and looked around for their home…

I posted about this back in 2006: Ants on Stilts for Science, but the webcast by NPR is worth a new post.

Disrupting Bacterial Communication to Thwart Them

Interrupting Bacterial Chatter to Thwart Infection

To measure their own numbers, bacteria produce, release, and detect chemical signals called autoinducers. As a population of bacteria grows, it releases more autoinducer into its environment. When individuals detect that a threshold level of autoinducer is present, they change their behavior – by releasing a toxin, for example.

Bassler and her colleagues disrupted these lines of communication by interfering with molecules called acyl-homoserine lactone (AHL) autoinducers, which drive quorum sensing among a kind of bacteria known as Gram-negative bacteria. Gram-negative bacteria include Pseudomonas, E. coli and Salmonella, and other disease-causing microbes. In the study, the team focused on Chromobacterium violaceum, which rarely infects human, but can be lethal to other organisms. C. violaceum lends itself to studies of quorum sensing because it produces a readily detected, bright purple dye when it detects that its population has reached a critical mass.
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The experiment shows that interfering with quorum sensing may provide an alternative to traditional antibiotics, Bassler says, and circumvent the problem of resistance that antibiotics foster by killing off susceptible bacteria but allowing resistant ones to survive and propagate.

Friday Fun: Bird Mimics Other Birds and More

The lyre bird, not only mimics the calls of other birds, buy also man made noises such as cameras, saws and chainsaws, in an attempt to impress potential mates. David Attenborough narrates the above clip.

Re-engineering the Food System for Better Health

Good food nation

According to the Centers for Disease Control, between 1980 and 2006 the percentage of obese teenagers in the United States grew from 5 to 18, while the percentage of pre-teens suffering from obesity increased from 7 to 17.
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Obesity is widespread due to our national-scale system of food production and distribution, which surrounds children – especially lower-income children – with high-calorie products…
90 percent of American food is processed – according to the United States Department of Agriculture – meaning it has been mixed with ingredients, often acting as preservatives, that can make food fattening.
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Now, in another report finished this October after meetings with food-industry leaders, the MIT and Columbia researchers propose a solution: America should increase its regional food consumption.
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Only 1 to 2 percent of all food consumed in the United States today is locally produced. But the MIT and Columbia team, which includes urban planners and architects, believes widespread adoption of some modest projects could change that, by increasing regional food production and distribution.

To help production, the group advocates widespread adoption of small-scale innovations such as “lawn to farm” conversions in urban and suburban areas, and the “10 x 10 project,” an effort to develop vegetable plots in schools and community centers. Lawns require more equipment, labor and fuel than industrial farming nationwide, yet produce no goods. But many vegetables, including lettuce, cucumbers and peppers, can be grown efficiently in small plots.
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As Albright sees it, the effort to produce healthier foods “fits right in with the health-care reform effort right now because chronic diseases are so costly for the nation.” America currently spends $14 billion annually treating childhood obesity, and $147 billion treating all forms of obesity.

Good stuff. We need to improve health in the USA. The current system is unhealthy and needs to be improved. The public good from improving the health of society is huge (both in terms of individual happiness and economic benefits).

Web Gadget to View Cell Sizes to Scale

Image of cell size gadget from University of Utah

The Genetic Science Learning Center, University of Utah has a nice web gadget that lets you zoom in on various cells to see how large they are compared to each other. Above see a red blood cell, x chromosome, baker’s yeast and (small) e-coli bacterium.

A red blood cell is 8 micron (micro-meter 1/1,000,000 of a meter). E coli is 1.8 microns. Influenza virus is 130 nanometers (1/1,000,000,000 a billionth of a meter). Hemoglobin is 6.5 nanometers. A water molecule is 275 picometers (1 trillionth of a meter).

Science Explained: RNA Interference

Explained: RNA interference

Every high school biology student learns the basics of how genes are expressed: DNA, the cell’s master information keeper, is copied into messenger RNA, which carries protein-building instructions to the ribosome, the part of the cell where proteins are assembled.

But it turns out the picture is far more complicated than that. In recent years, biologists have discovered a myriad of other molecules that fine-tune this process, including several types of RNA (ribonucleic acid). Through a naturally occurring phenomenon known as RNA interference, short strands of RNA can selectively intercept and destroy messenger RNA before it delivers its instructions.
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Double-stranded RNA molecules called siRNA (short interfering RNA) bind to complementary messenger RNA, then enlist the help of proteins, the RNA-induced silencing complex. Those proteins cleave the chemical bonds holding messenger RNA together and prevent it from delivering its protein-building instructions.

This article from MIT is one, of many, showing MIT’s commitment to science education of the public. Good job, MIT.

Dolphin Delivers Deviously for Rewards

Deep thinkers

At the Institute for Marine Mammal Studies in Mississippi, Kelly the dolphin has built up quite a reputation. All the dolphins at the institute are trained to hold onto any litter that falls into their pools until they see a trainer, when they can trade the litter for fish. In this way, the dolphins help to keep their pools clean.

Kelly has taken this task one step further. When people drop paper into the water she hides it under a rock at the bottom of the pool. The next time a trainer passes, she goes down to the rock and tears off a piece of paper to give to the trainer. After a fish reward, she goes back down, tears off another piece of paper, gets another fish, and so on. This behaviour is interesting because it shows that Kelly has a sense of the future and delays gratification. She has realised that a big piece of paper gets the same reward as a small piece and so delivers only small pieces to keep the extra food coming. She has, in effect, trained the humans.

Her cunning has not stopped there. One day, when a gull flew into her pool, she grabbed it, waited for the trainers and then gave it to them. It was a large bird and so the trainers gave her lots of fish. This seemed to give Kelly a new idea. The next time she was fed, instead of eating the last fish, she took it to the bottom of the pool and hid it under the rock where she had been hiding the paper. When no trainers were present, she brought the fish to the surface and used it to lure the gulls, which she would catch to get even more fish. After mastering this lucrative strategy, she taught her calf, who taught other calves, and so gull-baiting has become a hot game among the dolphins…

Too bad for the poor gulls but this is pretty cool. Plus it serves gulls right, one stole my breakfast a few years ago when I was down in Florida.

The Only Known Cancerless Animal

Unlike any other mammal, naked mole rate communities consist of queens and workers more reminiscent of bees than rodents. Naked mole rats can live up to 30 years, which is exceptionally long for a small rodent. Despite large numbers of naked mole-rats under observation, there has never been a single recorded case of a mole rat contracting cancer, says Gorbunova. Adding to their mystery is the fact that mole rats appear to age very little until the very end of their lives.

The mole rat’s cells express p16, a gene that makes the cells “claustrophobic,” stopping the cells’ proliferation when too many of them crowd together, cutting off runaway growth before it can start. The effect of p16 is so pronounced that when researchers mutated the cells to induce a tumor, the cells’ growth barely changed, whereas regular mouse cells became fully cancerous.

“It’s very early to speculate about the implications, but if the effect of p16 can be simulated in humans we might have a way to halt cancer before it starts.” says Vera Gorbunova, associate professor of biology at the University of Rochester and lead investigator on the discovery.

In 2006, Gorbunova discovered that telomerase—an enzyme that can lengthen the lives of cells, but can also increase the rate of cancer—is highly active in small rodents, but not in large ones.

Until Gorbunova and Seluanov’s research, the prevailing wisdom had assumed that an animal that lived as long as we humans do needed to suppress telomerase activity to guard against cancer. Telomerase helps cells reproduce, and cancer is essentially runaway cellular reproduction, so an animal living for 70 years has a lot of chances for its cells to mutate into cancer, says Gorbunova. A mouse’s life expectancy is shortened by other factors in nature, such as predation, so it was thought the mouse could afford the slim cancer risk to benefit from telomerase’s ability to speed healing.

While the findings were a surprise, they revealed another question: What about small animals like the common grey squirrel that live for 24 years or more? With telomerase fully active over such a long period, why isn’t cancer rampant in these creatures?

Engineered Circuits That can Count Cellular Events

Engineered circuits can count cellular events by Anne Trafton

MIT and Boston University engineers have designed cells that can count and “remember” cellular events, using simple circuits in which a series of genes are activated in a specific order.
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The first counter, dubbed the RTC (Riboregulated Transcriptional Cascade) Counter, consists of a series of genes, each of which produces a protein that activates the next gene in the sequence.

With the first stimulus — for example, an influx of sugar into the cell — the cell produces the first protein in the sequence, an RNA polymerase (an enzyme that controls transcription of another gene). During the second influx, the first RNA polymerase initiates production of the second protein, a different RNA polymerase.

The number of steps in the sequence is, in theory, limited only by the number of distinct bacterial RNA polymerases. “Our goal is to use a library of these genes to create larger and larger cascades,” said Lu.

The counter’s timescale is minutes or hours, making it suitable for keeping track of cell divisions. Such a counter would be potentially useful in studies of aging.

The RTC Counter can be “reset” to start counting the same series over again, but it has no way to “remember” what it has counted. The team’s second counter, called the DIC (DNA Invertase Cascade) Counter, can encode digital memory, storing a series of “bits” of information.

The process relies on an enzyme known as invertase, which chops out a specific section of double-stranded DNA, flips it over and re-inserts it, altering the sequence in a predictable way.

The DIC Counter consists of a series of DNA sequences. Each sequence includes a gene for a different invertase enzyme. When the first activation occurs, the first invertase gene is transcribed and assembled. It then binds the DNA and flips it over, ending its own transcription and setting up the gene for the second invertase to be transcribed next.

When the second stimulus is received, the cycle repeats: The second invertase is produced, then flips the DNA, setting up the third invertase gene for transcription. The output of the system can be determined when an output gene, such as the gene for green fluorescent protein, is inserted into the cascade and is produced after a certain number of inputs or by sequencing the cell’s DNA.

This circuit could in theory go up to 100 steps (the number of different invertases that have been identified). Because it tracks a specific sequence of stimuli, such a counter could be useful for studying the unfolding of events that occur during embryonic development, said Lu.

Other potential applications include programming cells to act as environmental sensors for pollutants such as arsenic. Engineers would also be able to specify the length of time an input needs to be present to be counted, and the length of time that can fall between two inputs so they are counted as two events instead of one.

Undergraduate Student Discovers Herbivorous Spider

Herbivory Discovered in a Spider

A jumping spider from Central America eats mostly plants, according to new research. Spiders were thought to be strictly predators on animals. The spider, Bagheera kiplingi, was described scientifically in the late 1800s, but its vegetarian tendencies were not observed until the 21st century.

“This is the first spider in the world known to deliberately hunt plant parts. It is also the first found to go after plants as a primary food source,” said lead author Christopher Meehan.
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Of the approximately 40,000 species of spiders known, Bagheera kiplingi is the only species known to be primarily herbivorous. Ironically, the vegetarian spider is named after the panther in Rudyard Kipling’s “The Jungle Book.” The spider inhabits several species of acacia shrubs involved in a well-known mutualism between the acacias and several species of ants.
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Previously, very few spiders had been seen consuming plants at all. Some spiders had been observed occasionally eating nectar and pollen, although the bulk of their diet was insects and other small animals.