A close relative of the bacteria infamous for seafood contaminations that often lead to fatal disease, the microbe Vibrio parahaemolyticus, is common in warm coastal waters like the Gulf. The long comma-shaped bacteria, slurped down with raw oysters, brings twisting cramps and nausea to 4,500 American shellfish aficionados each year.
But unlike some of its finicky peers, V. parahaemolyticus has a deep thirst for crude oil. "You can feed it exclusively oil," and it will thrive, said Jay Grimes, marine microbiologist at the University of Southern Mississippi.
As many have noticed, oil is not in short supply on the Gulf Coast.
Scientists have long known that the ultimate end of the crude oil spewing into the Gulf of Mexico from the damaged BP PLC well will rest in the hands of marine bacteria, single-cell organisms that have been purging the seas of oil from natural seeps for millenia, having only recently added human folly to their cleanup resume. Without these bacteria, whose numbers surge in response to hydrocarbons, enough oil would leak each year to coat the world's oceans in a fine film, molecules deep.
Beneath this awareness, however, sit vast reserves of uncertainty. Microbiologists are unsure which bacteria, feeding off the oil, are already growing exponentially in the Gulf. They are curious how long the bacterial growth will last once the oil's hard remnants drift down into ocean sediment. And no one seems certain how the surge in microbial life will alter the intricate, disentangling web of the Gulf's already weakened ecology.
One of the more pressing questions involves Vibrios, which, until the oil spill, were one of the primary threats to the region's vital shellfish business. While parahaemolyticus rarely causes serious disease, another Vibrio species, vulnificus, kills dozens of Americans each year, largely through seafood contamination. The disease, only recently discovered, has caused fierce debate between health officials and local Gulf politicians over raw oysters, the primary carriers of the disease.
Since Vibrio populations swell in the summer -- they love the heat -- this year there is a likely possibility, scientists say, that Vibrio growth could be further spurred, directly or indirectly, in response to the oil and the organic flotsam it has left behind.
"The question is: Will there be an inadvertent enhancement of the growth of these potential human pathogens?" said Rita Colwell, former director of the National Science Foundation and an expert in marine microbial life. "It's a question, and the answer is uncertain."
So far, hard evidence is scant. Grimes recently examined an oiled water sample taken by the research ship Pelican. The oil, likely exposed to dispersant, was finely divided. Using gene-staining technology, Grimes discovered several microbes attached to the droplet. Now glowing blue, they had been gorging. At least one was a Vibrio.
"There's no question bacteria, in general, increase following spills, and this includes Vibrios," said Jim Oliver, a Vibrio specialist at the University of North Carolina, Charlotte. Whether the pathogenic Vibrios "significantly increase is unsure, I would say, but they are coastal bacteria ... so [they] could well increase either as a direct result of oil degradation or as a side effect of the added nutrient levels."
The ingredients are there for heightened concern, Oliver added. The carcasses of bacteria feeding off the oil will increase overall nutrient levels as sweltering summer temperatures hit their peak. While there are natural controls, like bacterial viruses and protozoa, that can check Vibrio growth, those can be overwhelmed, studies have shown. And because of the cleanup, more people could be coming into direct contact with the bacteria.
"I think that combination could lead to very serious public health concerns," Oliver said.