Buzzing: 13-Year Periodic Cicadas Emerge

The humble vibrato of summer will crescendo a bit earlier this year in the U.S. South. Billions of cyclical cicadas will be out in full force starting this May, following a 13-year lull.

Having dropped to the ground from treetop eggs during the Clinton administration, the so-called "Great Southern Brood" (aka brood XIX) of cicadas spent more than a decade in a nymph stage underground nibbling on tree roots. But this year, the hefty hemipterans will all be roused from their burrows as the soil warms to crawl, for the first time, into the daylight in search of mates.

And 13 years in the making, the males' signature cacophony is certainly persistent. As St. Louis Zoo entomologist Jane Stevens explained in Scientific American in 1998, "The daytime noisemakers are indefatigable in calling for a mate."

How do they spend so long in their dank borrows, five to 46 centimeters belowground? Scientists are still trying to crack this and other cicada mysteries. But a 2009 study found that symbiotic bacteria that live inside cicadas' cells help produce essential nutrients that are otherwise lacking in the insects' earthy diets.

This brood isn't the only one that passes years underground—and by no means has spent the longest getting ready to make their entrance. There are about 15 broods of periodical cicadas (of the genus Magicicada), which surface in different regions of the U.S. in different 13 or 17 year cycles. The brood X "Great Eastern Brood" cicadas, for example, spent 17 years getting ready for their 2004 debut. The trusty annual crops of cicadas usually crawl out of the ground later in the season, often after the cyclical cicadas have laid their eggs and died.

Researchers still aren't sure why some of these riotous insects emerge in long and odd-yeared cycles. One hypothesis is that it helps to reduce competition for resources by minimizing the frequency with which broods are active at the same time. With each brood arriving in such large swarms, the sheer numbers might also help increase the odds that even if millions are picked off by predators, millions more will survive to reproduce. Birds are among the beneficiaries of these big periodic cicada years, along with scientists—and, apparently, hungry biologists. As Gene Kritsky, editor in chief of American Entomologist told NPR, "You can eat them. They taste to me like cold canned asparagus, very green."

Even if you choose to savor the song rather than the flavor of cicadas this spring in the South, rest assured that it's not likely to be as loud as 1998, when both the 17-year and 13-year cicada species overlapped—an event that happens only once every 221 years.

As for brood XIX, we'll expect to see—or at least hear—them again in 2024.

'Bacterial dirigibles' emerge as next-generation disease fighters

Scientists today reported development of bacteria that serve as mobile pharmaceutical factories, both producing disease-fighting substances and delivering the potentially life-saving cargo to diseased areas of the body. They reported on this new candidate for treating diseases ranging from food poisoning to cancer — termed "bacterial dirigibles" -- at the 241st National Meeting & Exposition of the American Chemical Society, being held here.

"We're building a platform that could allow bacterial dirigibles to be the next-generation disease fighters," said study leader William E. Bentley, Ph.D. "The concept is unique."

Bentley explained that traditional genetic engineering reprograms bacteria so that they produce antibiotics, insulin, and other medicines and materials. The bacteria grow in nutrient solutions in enormous stainless steel vats in factories. They release antibiotics or insulin into vats, and technicians harvest the medicine for processing and eventual use in people.

The bacterial dirigible approach takes bioengineering a step further. Scientists genetically modify bacteria to produce a medicine or another disease-fighting substance. Then, however, they give the bacteria a biochemical delivery address, which is the locale of the disease. Swallowed or injected into the body, the bacteria travel to the diseased tissue and start producing substances to fight the disease.

Bentley chose the term "bacterial dirigibles" because the modified bacteria actually have the fat-cigar look of blimps and zeppelins, those famous airships of yesteryear. In addition, the bacteria seem to float like a blimp as they make deliveries.

The prototype bacterial dirigible is a strain of E. coli that Bentley and colleagues developed at the University of Maryland in College Park, where he is Robert E. Fischell Distinguished Professor and Chair of the Fischell Department of Bioengineering.

"We have created a genetic circuit that endows E. coli with targeting, sensing and switching capabilities," Bentley explained. "The resultant cell is a bacterial dirigible – a cell that autonomously navigates and carries or deploys important 'cargo'."

The "targeting" molecule is attached to the outer surface of the bacteria. It gives the bacteria an ability to "hone in" on specific cells and attach to them — in this instance, the intestinal cells where other strains of E. coli cause food poisoning symptoms. Inside the bacteria is a gene segment that acts as "nanofactory." It uses the bacteria's natural cellular machinery to make drugs, such as those that can fight bacterial infections, viruses, and cancer.

The nanofactory also could produce signaling molecules that enable the dirigible to communicate with natural bacteria at the site of an infection. Some bacteria engage in a biochemical chit-chat, termed "quorum sensing," in which they coordinate the activities needed to establish an infection. Bacteria dirigibles could produce their own signaling molecules that disrupt quorum sensing, preventing bacteria from starting an infection.

In work on the prototype, Bentley's group showed that the re-engineered strain of E. coli did seek out and attach to intestinal cells growing in laboratory cultures. They also showed that the modified bacteria did produce chemical signals that triggered neighboring bacteria to make certain proteins that they don't normally produce. The results constitute proof of principle that the "bacterial dirigibles" concept can work, he said.

Using this approach, the nanofactory also could produce chemical signals that trigger cells lining the stomach or other parts of body to synthesize natural disease-fighting substances, such as immunoglobulins. Immunoglobulins are proteins used by the immune system to identify and destroy foreign objects, such as bacteria and viruses.

"The bacterial dirigibles can send out a strong signal to which disease-fighting cells of the body can respond," Bentley noted. "The chemical signals tell the cells to attack the body's foreign invaders, including the bacteria that cause food poisoning."

Bacterial dirigibles could be given to patients in the form of probiotics, live microorganisms that are beneficial to health like those found in certain kinds of yogurt, Bentley said. Doctors could also inject dirigibles into the bloodstream or directly into a diseased area, such as a tumor, he said.

Provided by American Chemical Society (news : web)