National Geographic : 1993 Aug
there's an all-important difference between biological plastics and the chemical synthet ics. Bioplastic is biodegradable; synthetics have a mirror-image molecular chain that inhibits biodegradation." Is the world responding to the prospect of bioplastics? ICI, the British chemical giant, produced 150 tons last year, said Professor Fuller, and environmentally minded German "greens" gladly pay more for biodegradable bottles made from it. Japan, critically short of landfill space, could be first to plunge into large-scale bioplastic production. T WO BACTERIA loom large in the struggle to provide humankind with food and fiber. They are Agrobacterium and Bacillusthuringiensis,known as B. t. to gardeners and farmers. Among their benefits, the two could lessen agriculture's dependence on chemicals used in pesticides. B.t. produces a miraculous natural insecti cide, best known for its effect on caterpillars. The bacterium, which contains a tiny protein crystal that burns through the insect's gut, exists in countless strains, each fatal to a spe cific insect. Applied as dust or spray, the prod uct causes few environmental side effects. B. t.'s precision, however, is a handicap in the marketplace, where it must compete with chemical insecticides that can kill many insects. Because sunlight destroys the protein crystal, the insecticide also has a brief life, and gardeners must reapply it every week or so. This limitation has been overcome by the Mycogen Corporation. "We transfer B.t.'s crystal-forming gene to a Pseudomonasbacte rium that has a tough, double-layer cell wall," said Thomas Larsen. "The cell walls encapsu late the crystal against sunlight, giving it greater field life. We call it the CellCap Sys tem." Applied as a spray of dead Pseudomo nas, a product using CellCap was the first genetically engineered pesticide to win EPA approval for release. In 1976 Israeli entomologist Yoel Margalith was surveying a mosquito-infested area of the Negev desert. On a puddle he spotted a mass of dead larvae. Laboratory analysis showed they had been killed by an unknown strain of B. t., now labeled B. t. i., for israelensis. The discovery marks a humanitarian mile stone. The World Health Organization and others spray B.t.i. on vast areas in Africa, Bacteria:Teaching Old Bugs New Tricks ENZYME POWER "It takes away all the dirt-that's how it's different," declares Tokyo resident Megumi Ishikawa of Attack, a Japanese detergent that uses bacterial enzymes to digest stains. The grime-fighting bugs were found in a rice field. Hot springs in Yellowstone National Park (fac ing page) yield bacteria with heat-resistant enzymes crucial to DNA research. Asia, and South America to control malaria bearing mosquitoes. B.t.i. also kills black flies, the carriers of river blindness, and spraying campaigns are eradicating the men ace in fertile river valleys of West Africa. A novel idea arose from B. t.'s success: Why not insert its crystal-growing gene directly into a plant? The plant itself would then combat pests, reducing the need for spraying. And the insect-killing trait would pass to ensuing gen erations of plants through the seeds. But how do you insert a bug's gene into a plant? The answer lay in yet another bug, the remarkable Agrobacterium tumefaciens. "It's known as the crown gall bacterium,"