Bacteria - TEACHING OLD BUGS NEW TRICKS

By Thomas Y. Canby

Like venom squirting from a fang, lethal cyanide poured daily from the Homestake Mine's gold-processing plant into South Dakota's Whitewood Creek. Mercury, arsenic, and sewage thickened the toxic flow. For a hundred years the stream ran gray and sterile through the Black Hills and beyond.

“Even 30 years ago people thought it was wrong,” recalls Jim Whitlock, a local resident. “But the Homestake Mine was the biggest gold producer in the Western Hemisphere. It meant money, jobs, everything.”

Then time caught up with the Homestake. Citizens, state, and nation demanded action. By the late 1970s the company had largely cleaned up its ore treatment. But the question remained: How to safely rid effluent of the cyanide used for separating out the gold?

“I thought bacteria could do it,” said Mr. Whitlock, today a Homestake biochemist. “I collected samples of water exposed to the poison. They held cyanide-tolerant bacteria that actually feed on the poison's carbon and nitrogen.

“We designed a bioreactor, a series of tanks in which the cyanide effluent moves slowly past feeding bacteria. It worked. We still flush the final product into Whitewood Creek. Only now it's clean.”

Today fishermen regularly pull trout from the once poisoned creek.

The triumph at Homestake already is legend in environmental circles. It does not stand alone. In the United States at least 50 cleanup companies apply the technology known as bioremediation, siccing microbes on everything from gasoline-soaked soil at the corner service station to EPA-designated Superfund sites strewn with the worst carcinogens.

This is a heady time to be a microbe. (“Microbe” is merely a convenient name for any of hundreds of thousands of species of microscopic organisms that flourish on earth; the most numerous are the ones we call bacteria.)

With clever coaching from microbiologists, bacteria and other “bugs” are being put to work in wondrous ways. “We've always been good at domesticating plants and animals,” said Jerry Caulder of the Mycogen Corporation of San Diego. “Now we're learning to domesticate bacteria.”

Some microbes serve as factories—making pharmaceuticals, pesticides, solvents, and plastics.

Some help make the snow at your ski resort.

Some separate gold and copper from ores, reducing the need for chemicals like cyanide.

Some rejuvenate tired oil wells.

Some make the enzymes for snipping DNA, the first step in genetic engineering.

Some are our fermenters, converting sugars into bread, beer, sauerkraut, cheese, yogurt, vinegar, wine.

And some microbes, of course, are age-old enemies, the invisible messengers of tuberculosis and cholera and other scourges. But those are relatively few. “Only one microbe in a thousand is a pathogen—what we think of as a germ,” said Lenore Clesceri of Rensselaer Polytechnic Institute in Troy, New York. “The rest, neither we nor the planet could live without. They make what we want, and they get rid of what we don't want. They are the workhorses of biotechnology.”

These tiny workhorses share a common characteristic: They can live as a single cell. Scoop up a teaspoon of garden soil, put it under a microscope, and you'll find several types of microbes—three of which you know already by their deeds.

The plump spheroids you see are yeasts, the fermenters that leaven our bread and brew our beer. Perhaps a million loll in your soil sample. By happy accident, yeasts may have become our earliest domesticates when our ancestors unknowingly harvested yeasts with wild grapes and attributed the miracle of wine fermentation to their gods.

The hairy cells are molds. Your slide may hold 200,000. These fungi are master decomposers. Those hairlike filaments hold powerful chemicals whose probings decompose our compost and the litter of the forest—and can lead to crop diseases and human cancer.

The amoeba-like organism you see is a protozoan—and in fact may be an amoeba. Many protozoans prey on soil bacteria, keeping their population in check. A mere 10,000 protozoans inhabit your sample, though not the most notorious, which cause malaria.

The rest you see—all one billion of them—are bacteria. Oldest of life-forms (for two billion years the only life on earth), they are structurally the simplest, lacking the cell nucleus found in other microbes. Most reproduce by fission: They multiply by dividing. Bacteria thrive as the planet's most abundant, most varied, most versatile, and most useful organisms—and among its most deadly.

These microbes dwell among us—and within us—in astronomical numbers.

At the moment you were born, all damp and wiggly, your body harbored no bacteria. But in hours they colonized this inviting ecological niche, arriving on the air, on doctors' hands, in mother's milk. Today you carry about a quarter of a pound. Billions are helping digest your last meal and, perhaps, excavating a cavity where your tooth brush fails to reach.

The ability of microbes to break down matter—both natural and man-made—helps explain why the world is looking at them anew.

“They are nature's recyclers,” said John A. Glaser of EPA's risk reduction laboratory in Cincinnati. “We can use this environmental process to clean up the environment.”

The process means big business for Groundwater Technology, Inc., of Norwood, Massachusetts. Specialists in treating polluted groundwater and soil, they have used the technology of bioremediation to clean up hundreds of sites around the world.

“One of the biggest problems is old gas stations,” said Louis Fournier, the firm's principal scientist. “A steel tank lasts only about 15 years; in the U.S. probably hundreds of thousands have leaked gasoline.

“Gasoline percolates through the soil until it floats on the groundwater. Then it breaks down into scores of other compounds, including benzene, a confirmed carcinogen. Unfortunately benzene dissolves in water.

“Microbes, used in concert with other approaches, can clean all this up.”

Where do they come from?

“They're already down there,” said Dr. Fournier. “The soil contains thousands of species of microbes, all living off one another's excretions. Our job is to give encouragement to the right bugs—the 5 or 10 percent that will eat the contaminant. We whet their appetites with side dishes of favored nutrients—compounds of nitrogen, phosphorus, oxygen.”

To see microbes in action, I sought out some sore spots among the nation's all-too-numerous waste sites. First stop: a Superfund project on the lower Mississippi, at the base of the mighty levee holding the river in check.

“The Old Inger Oil Refinery reprocessed dirty oil,” said Ralph Portier of Louisiana State University. “As you can see, the soil is black with contaminants—more than 200 toxic compounds.

“One option was to truck the soil to a landfill in Texas at a cost of 25 million dollars—an engineering ‘solution’ that simply moved the problem. The U.S. Army Corps of Engineers demurred, because excavating would undermine the levee.

“I identified bacteria that were already eating the pollutants and encouraged them to reproduce. Then we applied them to a contaminated test site. In nine months they cleaned it up. Full cleanup will cost an estimated ten million dollars—the first Superfund site approved for bioremediation.”

We drove along the river. Every few miles we passed a petrochemical plant. Near the impoverished community of St. Gabriel we stopped at the Ciba chemical plant. “This is my favorite project,” said Dr. Portier.

With company officials we gathered around a pilot bioreactor—four vertical tanks the size of phone booths. “They hold granules of carbon and diatomaceous earth, for bacteria to cling to. Water from chemical processes flows past, and the bacteria eat the contaminants. The company wants to install another dye plant, involving more chemicals. The bioreactor will solve environmental problems before they start. The new plant will create jobs, and some will go to St. Gabriel.”

Despite such successes, bioremediation has its detractors. Established engineering still favors cleanup by excavating and incinerating. In earlier years charlatans cleaning septic tanks sold “bags of bugs” that did little—discrediting bacteria. One criticism persisted: No hard scientific data supported bioremediation's apparent results.

“We needed to clear the air,” said John Wilson of the EPA research laboratory in Ada, Oklahoma. “I decided to spend taxpayers' money to research cleanup at a site using microbes—with every step monitored, every result recorded.”

Traverse City, Michigan, became his proving ground.

Pollution seems out of place in this resort town, wrapped on three sides by emerald forest and fronting on Lake Michigan. Traverse is also a samaritan city, home of a U.S. Coast Guard station whose helicopters respond to the distress calls of the region's many boaters.

In the late 1970s residents adjacent to the station became concerned about their well water. “It had a funny taste and smell,” recalled Irene Pickard, a retired health-care billing clerk. “It grew brownish and began to foam in the glass.”

Investigation revealed that aviation fuel had been leaking from the station's underground tanks, maybe for decades. Its invisible plume had moved a mile with the groundwater, beneath the Pickard family's house and beyond. In 1984 the Coast Guard hired Traverse Group, Inc., a bioremediation firm.

TGI drilled interdiction wells to pump out the fuel at the station boundary. “The effect on the plume was astonishing,” said William Korreck, then site manager for TGI. “With the spread of the spill halted, the indigenous soil microbes quickly did their work, and the plume collapsed on itself. After 18 months we could find no trace of it beyond the station.”

The concentration under the station became the focus of three experiments. Dr. Wilson's team at EPA set up to monitor. Interest was riveted on a dramatic new technology known as bioventing, pioneered by Robert Hinchee of Battelle Memorial Institute in Columbus, Ohio, among others. With John Armstrong, TGI's founder, I strolled the grassy test area above the spill. Every few feet white plastic well pipes thrust above the green like cemetery markers. Some carried air down to the polluted aquifer. Shorter ones drew air up through the soil—the key to bioventing.

“Air pumped down to the groundwater picks up the contaminants,” said Dr. Armstrong. “Then vacuum pumps draw the dirtied air back up. As the contaminants filter through the soil they are eaten by the native bacteria, which we encourage with nutrients.

“Air analyzed at the surface is clean. The microbes turn the soil itself into a bioreactor.”

“Bioventing is slow but cheap,” said Dr. Wilson. “It can reach under buildings and other surface obstructions. It should be the technology of the future.”

Like fuels from leaking tanks, other pollutants are woefully common. Microbes find growing roles with each.

Paint-stripping sites: Kelly Air Force Base in San Antonio, Texas, strips old paint from C-5s—half a million pounds of pollutants a year that few landfills will accept. Other military bases and commercial aircraft contribute similar noxious debris.

Could microbes star as strippers? Their show hit the road at a laboratory in Utah.

“Two bacteria and a fungus remove the paint,” said Gail Bowers-Irons of Technical Research Associates in Salt Lake City. “We found them at an old paint landfill.” She showed me a bottle holding liquid and a chunk of painted metal. The microbes were loosening paint from the metal as if peeling a banana.

“Once the paint is removed, we have a bacterium that eats it,” said Mrs. Bowers-Irons. “The bacterium came from a junk pile. We look for helpful bugs wherever equipment is falling apart.” A pilot plant for consuming paint is scheduled to be built at Kelly Air Force Base next year.

By sorting 20,000 mutants of a single strain of bacteria, Malcolm Shields of the University of West Florida in Pensacola isolated the most effective form of a bug known to degrade TCE, or trichloroethylene. This ubiquitous contaminant, found in solvents for removing grease and paint, pollutes soil and groundwater at thousands of sites.

Wood-preservative sites: At hundreds of locations across the country, companies treat telephone poles and railroad ties. They use some of the harshest chemicals known. Creosote, the old standby—now tightly controlled—reeks of polyaromatic hydrocarbons, PAHs, many of which are carcinogens.

“Many operations also tend to be marginal, unable to meet environmental costs,” said EPA's John Glaser. “They go bankrupt and walk away from their mess.”

Digging through preservative sites in Florida, James Mueller of SBP Technologies, Inc., discovered a bacterium that degrades the carcinogenic PAHs. Now patented, it has been successfully tested in bioreactors at Pensacola, where the now-defunct American Creosote Works contaminated an aquifer and soil with thousands of gallons of creosote and pentachlorophenols.

Coal-gas sites: At the turn of the century many cities illuminated streets and homes with “town gas” made from coal. An estimated 1,500 plants were once active, many on what is now prime real estate in the East.

“The contaminants—PAHs, creosote, coal tar—glue the soil together, making it hard to get nutrients, pollutants, and bacteria to interact,” said Kennedy Gauger of the Radian Corporation in Austin, Texas. “We're working on slurrying the soil, making it more accessible.”

What about oil spills? Can we help native bacteria clean them up? The 1989 Exxon Valdez spill in Alaska provided promising results. “We marked out plots on contaminated beach,” said Hap Pritchard of the EPA research center in Gulf Breeze, Florida. “We designated some for treatment with fertilizers and some as controls with no treatment. In tests conducted over two summers, oil in the treated plots degraded two to four times as fast as that left to natural processes.”

Can we apply microbes to a spill, instead of simply stimulating those already in the soil or water? The merits are hotly argued; skeptics claim that introduced bacteria can't compete with hardy natives. EPA is currently developing standards for evaluating such methods.

Meanwhile an aggressive Texas firm, Alpha Environmental, has built a worldwide business applying its oil-eating microbes to petroleum-polluted sites. Alpha claims that a proprietary catalyst speeds reproduction of microbes and helps sustain the bugs as well.

Microbiologists happily capitalize on a phenomenon they don't fully understand: Bacteria break down chemicals from which they derive no nourishment or other clear benefit.

Some of these chemicals are tough. PCBs, TCE, and the like were designed to endure: Their molecules resist microbial attack. Yet in nature bacteria crack them. This odd behavior is called co-metabolism. The General Electric Company has demonstrated co-metabolism of PCB contaminants that it had discharged into the Hudson River years ago.

“Our job,” said Dr. Pritchard of EPA, “is to understand co-metabolism so we can encourage it in bioremediation.”

Recently scientists discovered another of nature's defenses against contaminants: the broad presence of microbes that have previously adapted to environmental change existing in a state of suspended animation.

“In times of stress,” said David L. Lewis of EPA's Athens, Georgia, research lab, “such as climatic change or the appearance of chemical pollutants, the quiescent microbes are activated. They impart a ‘memory’ to ecosystems, allowing them to cope with new stresses.”

To work their magic, microbes secrete enzymes. All of us produce these remarkable proteins; they serve as catalysts for the chemical processes that take place every second in our bodies. Microbes evolved enzymes first, billions of years ago. The enzymes in turn gave rise to the ancient art of fermentation.

The master fermenters, many authorities agree, are the Japanese. Using enzymes produced by fungi and bacteria, they ferment their esteemed sake and beer, their miso, their malodorous bean dish, natto. And, of course, that most essential condiment, soy sauce.

The Japanese began producing soy sauce five centuries ago. At the Kikkoman Corporation in Tokyo, I saw the simple ingredients of the sauce: soybeans, wheat, salt, and the mold Aspergillus.

“The mold is one of our treasures,” said an employee. Alluding to the Japanese reverence for forefathers, he added: “The production workers call Aspergillus‘ancestor.’”

From Japan I brought home a box of detergent and gave it to my wife, Susan, prettily gift wrapped. “Romantic,” she muttered. But she relented with the first wash using microbe made Atakku (Attack). Unavailable in the U.S., it has captured half of Japan's two-billion-dollar market.

Attack joined a flow of innovations that emerged from the laboratory of Koki Horikoshi and his celebrated Superbugs Project. He unearthed scores of bacteria intriguing to science and beneficial to Japanese industry.

“My fascination is bacteria that thrive in extreme environments,” said Dr. Horikoshi. “I discovered the Attack bacterium in a rice field; it survives alkalinity that is lethal to most microbes. It produces an enzyme that penetrates the dirt-holding niches in cotton fabrics—how, we still don't know.”

“A Jug of Wine, a Loaf of Bread ...” Poet Omar Khayyám could have been a microbiologist, so neatly did he link these products of fermentation.

“Both use the yeast Saccharomyces,” said Gary Sanderson of Universal Foods Corporation in Milwaukee. “The yeast converts sugars in the grain or grapes to carbon dioxide and alcohol. In the bread the carbon dioxide bubbles become trapped by the dough, causing the bread to rise. The alcohol boils off during baking but leaves a sweetness. Wine is the reverse—you retain the alcohol and permit the carbon dioxide to escape.”

A thunderous new dawn for microbes as workers broke in California in 1973. Scientists Stanley Cohen and Herbert Boyer spliced the gene of a toad into the genes of a bacterium. This remarkable feat signaled the birth of modern biotechnology. Now microbes could be tailored to create medical and other products. These strains could then be mass-produced in large tanks.

Bacteria had been groomed for the task. “They have been intensely studied, particularly in medical research,” said Paul Schendel of the Genetics Institute in Cambridge, Massachusetts. “We know more about them than about any other living system.”

Much of this research focused on Escherichia coli, found by the millions in our large intestines. When gene splicing went commercial, E. coli became the bacterium of choice for cloning and mass-producing new materials. The first product brought security to more than four million diabetics across the United States. It flowed from Eli Lilly and Company in Indianapolis.

The pharmaceutical giant was erecting a new facility when I visited. “It will process Humulin, our trade name for human insulin,” explained Andrew Russell as we trooped through the present overtaxed plant. Tanks rose three stories high; inside, trillions of genetically engineered E. coli were manufacturing the vital drug.

“Before we learned to make insulin,” said Dr. Russell, “the only sources were cattle and swine pancreases. There was fear that the demands of an increasing population would exceed supply. Then Genentech, Inc., of San Francisco, managed to transfer the insulin-making gene to bacteria. Lilly developed the difficult technology of producing the bacteria in large tanks and isolating and purifying the drug. The crisis was avoided.”

(Ironically, a particularly virulent strain of the E. coli bacteria was responsible for several deaths after children ate contaminated hamburger meat in fast-food restaurants in the Pacific Northwest this year. That strain causes illnesses that can lead to anemia, kidney failure, and strokes.)

Microbial factories could spread beyond medicine into products of other industries. There are, for example, microbes whose tiny bodies bulge with plastics.

“We think of plastics as new materials,” said R. Clinton Fuller of the University of Massachusetts at Amherst. “But bacteria have been making them for 3.5 billion years.

“Many species make polyesters almost identical to those used in synthetic fibers. But there's an all-important difference between biological plastics and the chemical synthetics. 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.

Two bacteria loom large in the struggle to provide humankind with food and fiber. They are Agrobacterium and Bacillus thuringiensis, 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 insecticide, 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 specific insect. Applied as dust or spray, the product 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 Pseudomonas bacterium that has a tough, double-layer cell wall,” said Thomas Larsen. “The cell walls encapsulate the crystal against sunlight, giving it greater field life. We call it the CellCap System.” Applied as a spray of dead Pseudomonas, 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 milestone. The World Health Organization and others spray B.t.i. on vast areas in Africa, 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 menace 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 generations 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,” said Johnie Jenkins of the U.S. Department of Agriculture Research Service in Starkville, Mississippi. “We believe Agrobacterium makes an enzyme that enables it to snip a plant's chromosome and insert its own gene. The gene causes the plant to produce tumors, or galls. These form food for the bacterium.

“To change a plant's genetic structure, we remove the tumor-inducing gene from Agrobacterium and replace it with the gene we want for the plant—one that produces, say, a B.t. crystal. Agrobacterium then inserts it into the plant's chromosome.”

Agrobacterium's performance in Starkville could alter the future of agriculture.

There and at a dozen other sites, Monsanto is testing cotton plants implanted with the B.t. gene for killing caterpillars. The tests aim at reducing the frequent drenchings with chemicals required to protect the 14 million acres of cotton in the U.S.—a staggering 35 percent of all insecticides used on major crops.

Slipping in mud from an overnight rain, Dr. Jenkins and I surveyed his cotton patch. The engineered plants were easy to spot—bent over by the weight of their healthy bolls. Unaltered plants stood erect, most of their bolls destroyed by worms. “The difference is a single gene,” he said. “Monsanto hopes to commercialize the advance through seed companies in the mid to late 1990s.”

Critics argue that the target pests will soon evolve genetic resistance to B.t. Another uncertainty lurks in the shadows. Will a public outcry scuttle the project?

Americans have shown concern about the introduction of genetically engineered organisms into the environment. True, the Mycogen release of CellCap products won approval, but those introduced microbes were dead.

Mindful of public feeling, Monsanto and groups cooperating in the cotton experiment—EPA, USDA, Mississippi State University, and the state of Mississippi—have maintained rigid safety precautions. Public hearings preceded planting the first cotton.

Dr. Jenkins breathes optimism. “The alternative to our work is continued, massive pesticide use. I think we're on the side of history.”

Agrobacterium opens many doors for biotech companies. The DNA Plant Technology (DNAP) lab in Oakland, California, is aiming an introduced gene at fungi that cause rot in supermarket vegetables. Other DNAP genes prolong the sweetness of peas and change the color of roses and chrysanthemums.

Microbes have joined the work force in other areas:

Biomining: “Spanish miners knew in the 1700s that by running water on piles of copper ore, they caused free copper to seep out,” explained Henry Ehrlich of Rensselaer Polytech. “Unknown to them, the moisture stimulated bacteria to oxidize the sulfur binding the copper in the ore.”

Today perhaps a quarter of all U.S. copper is processed by bioleaching. In Brazil, Australia, and South Africa, gold mines use microbes to treat the raw ore before final processing with cyanide.

Biosensors: When a herbicide spilled into California's Sacramento River in 1991, state authorities quickly applied a classic test for toxicity, immersing rainbow trout and watching to see if they lived or died. Today authorities are switching to a bacterial device developed by Microbics Corporation of Carlsbad, California. The size of a small typewriter, this sensor capitalizes on the trait of many bacteria to luminesce, like lightning bugs. The bacteria do so less brightly when in contact with harmful material.

Enzymes made by bacteria integrate with electronics in sophisticated sensors developed by biotechnologist Isao Karube of the University of Tokyo. Dr. Karube's enzymes measure the alcohol content of wine and beer and the freshness of sushi. Placed in hospital toilets, the sensors monitor the health of patients, as indicated by minerals deposited with urine.

Enhanced oil recovery: Microbes play a growing role in wringing oil from faltering wells. The opportunity is enormous. In U.S. oil fields an estimated 50 billion barrels await improved recovery techniques.

“Hundreds of wells are stimulated yearly using microbes,” said Thomas E. Burchfield of the National Institute for Petroleum and Energy Research in Bartlesville, Oklahoma. “For example, bacteria remove clogging paraffins. A company can inject microbes down a well or simply stimulate the bugs already there with nutrients—most often molasses.”

Coal desulfurization: The acid rain that threatens lakes and forests in North America traces in large measure to sulfur from coal combustion. Bacteria show promise of removing much of that sulfur before the coal is burned. Research is under way at the Institute of Gas Technology in Chicago and DOE's Idaho National Engineering Laboratory.

Nitrogen fixation: French chemist Louis Pasteur recognized in the 1800s that soil microbes are essential to life; they are the primary force for fracturing tough molecules of atmospheric nitrogen and making it available for plants. These bacteria, often of the genus Rhizobium, live in the roots of plants, principally legumes.

Agriculturists have sought to extend this process to other crops and thus reduce our dependence on chemical fertilizers that pollute the environment. It has proved a challenge.

“Soil teems with Rhizobium strains,” explained Jo Handelsman of the University of Wisconsin at Madison, “but most of them are poor nitrogen fixers, even though they are well adapted to their niches. We can find efficient nitrogen-fixing Rhizobium strains, but it's difficult for them to compete. We're trying to make them more competitive by manipulating their genes.”

Making snow, stopping frost: In 1975 Steven Lindow of the University of Wisconsin discovered that bacteria living on plant leaves encourage the formation of frost. He traced the phenomenon to Pseudomonas syringae, whose cell wall contains a protein that causes water molecules to align so that they form ice crystals.

Picking up the ball, colleague Trevor Suslow developed Snomax, a snow-making powder formulated from dead P. syringae. Today the product, licensed by Genencor International, Inc., is mixed with water and sprayed on ski slopes around the world to generate snow.

If bacteria induce frost, could damaging frost be prevented by ridding crops of the bacteria? Each year U.S. farmers spend millions of dollars fending off frost with wind machines and water sprinklers.

Drs. Lindow and Suslow pursued the idea, adopting the name Frostban. They removed P. syringae's ice-nucleating gene and grew the frost-free bugs in tanks. Sprayed on leaves, the altered bacteria crowd out the frost inducers.

During the 1980s the scientists sought to release the altered bacteria on California potatoes and strawberries. Their efforts stirred tumult from environmental activists. Jeremy Rifkin of the Foundation on Economic Trends and others sued to halt field tests in 1983. Volleys of new test applications met fresh volleys of objections. Finally in 1987 Dr. Suslow obtained permission to test the bacteria on strawberries, Dr. Lindow on potatoes. They succeeded in completing their tests, although in both experiments vandals ripped up plants.

Results showed substantial frost reduction. But the industry lost momentum for introducing altered bacteria.

“During that time,” said Dr. Suslow, now with DNAP in Oakland, “we were also able to identify naturally occurring bacteria that can crowd out the frost inducers.” In 1992 EPA registered several of these naturally occurring strains for field use.

How safe are microbial releases? Scientists acknowledge that in the early days, guidelines for control of bacterial releases were lacking. They believe safeguards now exist, through both legal requirements and adherence to time-tested research standards.

“I can't see the Australian rabbit problem happening,” said Lenore Clesceri of Rensselaer, alluding to public fears of runaway bacteria strains.

“We've experimented with engineered bacteria for decades,” declared Robert Stevenson, director emeritus of the nation's bacterial bloodlines at the American Type Culture Collection in Rockville, Maryland. “We've had no trouble, partly because of the earlier concerns.”

Before quitting my coverage, I visited bacteria paradise—a sewage-treatment facility. I chose a key one: Maryland's Back River plant, main line of defense between Baltimore's torrent of human and industrial wastes and the effluent-burdened Chesapeake Bay.

“We screen the wastes, settle them out, and use a pinch of chemicals,” explained manager Gerry Slattery, “but the bugs are the heart of it. The wastes feed more than four million pounds of bacteria. Sometimes I wonder who's working for whom.”

We visited the secondary treatment area—great troughs aflow with dark liquid. “For every pound of sewage that arrives, we unleash ten pounds of bacteria. They're lean, they're hungry, and they grab.”

We went to the outfall, where the final effluent enters the bay. Minnows schooled beside a long concrete pier, and fishermen pulled up white perch. “The treated effluent,” said Mr. Slattery, “is much cleaner than the regular bay water.”

I get your message, Mr. Slattery: We look after the bugs, and they will help us look after planet Earth.

Source: National Geographic, August 1993.