|Send to printer »|
Insight & Intelligence : Jun 17, 2010
Can Microbes Help Stem the BP Oil-Spill Disaster?
Major innovation is desperately needed to ensure bacteria can be used safely and effectively.!--h2>
Current technology used by BP is proving hopelessly inadequate in curbing the tide of oil gushing from beneath the Gulf of Mexico. Now, novel technologies that remain untested at such an incomprehensible scale will be needed in anticipation of years of remediation to resuscitate a dying ecosystem.
“It is of grave concern,” David Kennedy of the National Oceanic and Atmospheric Administration (NOAA), said back in April. “And the efforts that are going to be required to do anything about it, especially if it continues, are just mind-boggling.”
On March 24, 1989, the tanker Exxon Valdez en route from Valdez, Alaska, to Los Angeles ran aground on Bligh Reef in Prince William Sound, Alaska. It spilled approximately 10.9 million gallons of its 53 million gallon cargo of crude oil. Driven by a storm, the oil quickly covered about 1,100 miles of noncontinuous coastline in Alaska. By comparison, as of June 11, 90 million gallons of oil had spurted into the Gulf, according to the new worst-case estimate from the government, which anticipates 20,000–40,000 barrels (about 42 gallons per barrel) leaking daily. This number keeps changing, though and has even gone up to 60,000 barrels a day.
Coast Guard Admiral Thad Allen, who leads the government's relief effort, said in June, “We're no longer dealing with a large, monolithic spill. We're dealing with an aggregation of hundreds of thousands of patches of oil that are going in a lot of different directions.” He noted that while cleaning up the oil spill on the surface will go on for a couple of months after the well is plugged, long-term issues of restoring the environment and the habitats will take years.
Bioremediation may have some role to play in that restoration provided the cure isn’t worse than the disease. Bioremediation involves using microorganisms or their enzymes to return environments altered by contaminants to their original conditions. In the case of oil spills multiple techniques may be used, including the addition of nutrients to the environment to enhance and facilitate crude oil decomposition by specific bacteria or the introduction of oil-eating bacteria. The former approach was used as part of the cleanup effort after the Exxon Valdez spill. The addition of bacteria has been less successful.
Lessons from Exxon Valdez
Bioremediation protocols employed during cleanup of the Exxon Valdez oil spill effectively demonstrated that application of nutrients in the form of fertilizer (nitrogen and phosphorus) could increase oil biodegradation rates. At the time, however, fertilizers used to boost bacterial populations caused some concern, mostly focused on the 2-butoxy-ethanol component in Inipol™ and its potential toxicity to wildlife and cleanup workers. Besides safety guidelines being followed to protect workers during application of fertilizers Inipol and Customblen, wildlife deterrents were used during the first 24 hours when toxicity was of most concern.
Ten days after treatment, the surfaces of the oil-blackened rocks on the shoreline turned white and appeared to be free of surface oil. The striking visual results strongly supported fertilizer application, which sustained higher numbers of oil-degrading microorganisms in oiled shorelines, according to EPA’s 1990 interim report. Additionally, the EPA noted, biodegradation rates were enhanced as evidenced by the chemical changes detected in recovered oil from treated and untreated reference sites.
But while encouraging microbe growth with biostimulation on contaminated shorelines appears useful, unleashing oil-eating microbes themselves has produced less than stellar results. For example, biotreatment using a bacterial culture from Alpha Environmental was deployed following a spill that occurred on June 8, 1990, following an explosion on the Norwegian tanker Mega Borg. An estimated 100,000 barrels of crude oil were burned or released into the Gulf of Mexico, 57 miles southeast of Galveston, during the next week.
Bioremediation tests were conducted on June 15 and 18, 1990. “These were the first tests of a bioremediation agent on an oil spill in open waters in the United States,” the NOAA incident report noted. “The bioremediation agent used was AE BioSea Process, developed by Alpha Environmental. AE BioSea Process contains oil-metabolizing bacteria and nutrients. The results of the tests were inconclusive.”
While the Texas General Land Office said that the bioremediation was effective, independent observations indicated that treated oil changed in physical appearance and may have emulsified as a result of addition of the Alpha product. Chemical analyses on samples from impacted and reference sites failed to demonstrate that treatment with the Alpha product enhanced rates of petroleum biodegradation.
Genetic Engineering vs. Experimental Evolution
Evolugate, a Florida company developing microbes for bioremediation, says that adding microbes to the site of a spill hasn’t worked well before because the microbes haven’t been adapted to the specific environment in which they need to survive. The firm is evolving microbes specifically to survive on oil from the Gulf spill in the Gulf environment by maintaining populations of microbial cells under controlled conditions of growth and environment for an indefinite duration. It says that this is a prerequisite for experimentally evolving natural isolates of wild-type species or recombinant strains.
The company grows the microbes in proprietary continuous cell culture vessels to select microbes that have higher proliferation rates under specific conditions. The innovation behind Evolugate’s continuous culture vessels is that they are engineered to prevent microbes from sticking to the walls, a common strategy by which microbes evade selective pressure in other continuous culture technologies.
The Evolugate technology works via partial dilution: As a culture grows and becomes saturated, a small proportion of the grown culture is replaced with fresh medium, allowing the culture to continually grow at close to its maximum population size. Thomas Lyons, Ph.D., principal research scientist and board member of the firm, told GEN that in adapting the microbes for the Gulf oil spill, “we add more microbes every day to bolster genetic diversity.
“When we first started the culture we saw a die-off, and we expected that the dispersants and oil in the Gulf water-containing medium would kill some microbes. But after one week we saw a huge increase in cell density suggesting that adaptive variants arose. Within two weeks we already have robust growth on oil samples taken from the Gulf.
“The beauty of what we do is that we have built in evolutionary trade-offs: The longer the microbes spend evolving to the oil the less robust they become under other conditions. Once the oil is gone they will lose their competitive advantage and will no longer survive in that environment.”
Dr. Lyons noted that producing such designer microbes through genetic engineering would be hard to pull off. Oil is so full of complicated substances that jamming all the genes needed to digest and metabolize it into a single microbe and then expecting it to reproduce and flourish might be asking too much, he said. Experimental evolution, on the other hand, simultaneously changes metabolic capabilities as well as optimizes growth rates.
He also pointed out that right now the company’s proposal to select and introduce designer oil-eating microbes into the Gulf is in BP’s hands. “It’s in their pipeline, but we are not waiting for a response. We know our approach stands the best chance to make bioremediation work, and we are proceeding accordingly. ”
Genetic engineers did indeed have a shot at enhancing oil-eating microbes. One species of oil eaters in the genus Pseudomonas was used during the Valdez cleanup, but it didn’t work efficiently or very quickly. The oil-eating superbug was developed at General Electric in 1975 by Ananda Mohan Chakrabarty, Ph.D., now distinguished professor of microbiology and immunology at the University of Illinois college of medicine laboratories.
To underscore Dr. Lyons’ point, while there are four oil eaters in this bacterial genus, each uses a different component of the oil as its food source and they all compete with one another when added to the same oil sample. In 1981, Dr. Chakrabarty received a patent on a genetically modified Pseudomonas bacterium that would eat up oil spills, the first patent of its kind; he was the first person to win a patent on a living organism.
Dr. Chakrabarty and his team inserted plasmids from all four species of the oil eaters and put them into a single microbe. While these plasmids would usually not operate together in the same cell, exposing the cell to ultraviolet light caused the plasmids to join into one that could express components of all four pathways of the original plasmids so that several oil components could be broken down.
Time for Creative Thinking
One problem with this creative approach to digestion, however, is that the microbes don’t eat enough nor quickly enough; it takes a lot of them a few days to go through an eyedropper full of oil. There is also concern over what the environmental impact of releasing engineered bacterial strains might be. Additionally, some have pointed out that in the case of oil-eating bacteria, oil companies might not want organisms literally eating their lunch.
Naturally seeping oil in the Gulf already feeds some microbes; low level inputs of hydrocarbons to the oceans, including natural slow oil leaks into the Gulf of Mexico in the form of geological seeps, pine droppings, etc., exist as natural marine ecosystem components. Thus, according to marine biologists, some bacteria within the marine microbial community have evolved the ability to break down hydrocarbons and exploit the considerable energy stored in the chemical bonds of these compounds.
Such organisms aren’t very prevalent, though, since other sources of food are more appealing, pointed out Terry Wade, Ph.D., deputy director of environmental science at Texas A&M University. “It’s like going into the supermarket and instead of buying a steak or a potato, eating the floor tiles.”
Right now ingenuity and insight into using microbes safely to help clean up the oil mess is desperately needed. Sitting around gob-smacked won’t help anything, and environmentalists firmly opposed to the introduction of any organism into the environment will need to suspend disbelief long enough to try desperate measures.
Patricia F. Dimond, Ph.D., is a principal at BioInsight Consulting. Email: [email protected].
© 2013 Genetic Engineering & Biotechnology News, All Rights Reserved