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Scrambling for the exits and carrying the helpless, they perched ankle- and then knee-deep atop the wings as an improvised armada of tour boats and ferries streamed to their rescue ... witnesses described a scene of level-headed teamwork to rescue the weak and infirm.
—The Washington Post, January 16, 2009 (1)
We at once see that those animals which acquire habits of mutual aid are undoubtedly the fittest ... we may safely say that mutual aid is as much a law of animal life as mutual struggle but that, as a factor of evolution it most probably has a far greater importance.
—Prince Pyotr Kropotkin, 1902 (2)
Bacteria communicate extensively with each other and employ a communal approach to facilitate survival in hostile environments.
—Shadaba Asad and Steven M. Opal, 2008 (3)
MUTUAL AID AND QUORUM SENSING
The masterful ditching in the Hudson River on January 15 of US Airways Flight 1549 and the rescue of all its 155 passengers provided high drama on a cold winter day. That "Miracle on the Hudson" preoccupied national television from the start and produced a real-life aviation hero, Captain Chesley Sullenberger. It also evoked a behavioral response that a century ago was called "mutual aid" by Prince Kropotkin (2)
and nowadays would be described "quorum-sensing" by microbiologists (3)
.
Within minutes after the plane alighted safely on the frigid Hudson, hatches opened and passengers, guided by attendants, emerged in orderly fashion through the emergency exits. "Some passengers began to wail, but witnesses described a scene of level-headed teamwork to rescue the weak and infirm ... (1)
" The Airbus remained adrift and partially submerged in the ice-cold water. Groups of passengers spread out on both wings of the jetliner; then as dry space on the wings gave out, a few moved to rafts. Within minutes, the drifting Airbus was surrounded by ferry and sightseeing boats, then by police vessels, fireboats, tugboats, and Coast Guard craft. Their crews tossed life rings and pulled the passengers to safety, their prows held the plane in place against the current. Helicopters brought wet-suited police divers, who dropped into the water to help with the rescue.
We’d call that kind of response mutual aid, for sure. But, what about that optimal clustering of folk on the teetering wing, that biofilm of rescue rigs in the water, that bobbing flotilla of vessels securing the plane, the airways abuzz with signals of distress and rescue? Why that sounds a lot like "quorum sensing" (4)
an evolutionary strategy used by microbes to effect a "coordinated population response ... explaining both cooperation and communication (5)
."
LET THEM BE SEA CAPTAINS IF THEY WILL
Another theme emerged: among the first ferry captains to arrive at the scene was Brittany Catanzaro, the 20 year-old Captain of the New York Waterways Ferry, Thomas Kean. It occurred to me that the drama of the Airbus on the Hudson was a prima facie argument for the equal rights amendment. Brittany Catanzaro and her crew plucked 24 passengers from the ditched flight to safety. "I’ve been on the water since I was 2 years old," the Captain told The New York Times "I pulled out of Pier 79, I looked for any kind of southbound traffic, and I saw the plane there ... It was hard to stay next to it, but you practice that by throwing life rings in the water and trying to stay alongside them (6)
."
The pioneering American feminist, Margaret Fuller, would have been proud. Fuller, who served Horace Greely as America’s first female foreign correspondent, argued for women’s equality in the moral, social, and occupational spheres. Her 1845 work, Woman in the Nineteenth Century, anticipated Captain Catanzaro’s feat by over a century and a half:
But if you ask me what offices they may fill, I reply—any. I do not care what case you put; let them be sea captains if they will. I do not doubt there are women fitted for such an office ... (7)
Neither would Fuller have doubted the fitness of Sheila Dale, Donna Dent, and Doreen Welsh, the three veteran flight attendants who safely guided the passengers from seat, to hatch, to wing, to shore. Each was over 50 years old and retained her job thanks to legal action taken by Eulalie Cooper, a flight attendant who in the sex-kitten days of the 60’s was fired by Delta Air Lines for being married. (8
, 9)
Fuller ranked among our nation’s leading literary figures in the ante-bellum period; she had edited The Dial with Ralph Waldo Emerson and became a cultural critic for the New York Tribune (10)
. She shared the meliorist convictions of the Brooke Farm transcendentalists who, half a century before Prince Kropotkin, believed that mutual aid was a human obligation:
With simultaneous vibration the hearts of all their circle acknowledged the divine obligation of love and mutual aid between human beings. Food, clothing, medicine were all offered freely ... (11)
In the course of her foreign adventures, she married the Marquis Ossoli, an Italian patriot who fought bravely on the barricades for the Roman Republic against the royalist-papal armies of France and Austria during the Revolution of 1848–1849. Fuller freed herself to work day and night as a volunteer nurse in the Tiber Island hospitals. In those bloody field stations, as a posthumous account had it, "the weather was intensely hot; her health was feeble and delicate; the dead and dying were around her in every stage of pain (12)
."
Ironically, Fuller died less than five years after her sea captain plea, because of the unfitness of a male sea captain in waters around New York. On July 19, 1850, Margaret Fuller, her husband, and infant son were drowned in a shipwreck on her return voyage from the Italian wars. An inexperienced first mate had run the merchantman Elizabeth aground on a sandbar off Fire Island and her body was never recovered. Days later, her old friend Henry David Thoreau wandered the sands looking for remnants of the Ossolis, but nothing had washed ashore (10)
. If only the Elizabeth had been tended to by a sea captain as professional as Brittany Catanzaro!
AN ANARCHIST EDITOR OF NATURE
Prince Pyotr Kropotkin (1842–1921), who fathered the principle of "Mutual Aid", was no mean feminist himself. He had taunted his Czar, Alexander II, who in turn had him imprisoned before the prince found refuge in England at the end of the century:
In spite of the open hatred of Alexander II for educated women,—when he met in his walks a girl wearing spectacles and a round Garibaldian cap, he began to tremble, thinking that she must be a nihilist bent on shooting at him; in spite of the bitter opposition of the state police, who represented every woman student as a revolutionist; in spite of the thunders and the vile accusations ... there are now in Russia more than six hundred and seventy women practicing as physicians (13)
The Prince, a natural scientist who had served as secretary of the Russian Geographical Society, arrived in London in 1886 and soon called at the offices of Nature, his favorite journal. He was "most cordially received" by a sub-editor, Mr. J. Scott Keltie, who was looking to increase the journal’s international coverage. Kropotkin, working under the exile’s pseudonym of Levashóff, showed the approving Keltie a few samples of his writing and soon the anarchist prince was given a table in the office of Nature and asked to review foreign publications and books. The multilingual Prince performed these editorial duties flawlessly until "One day, however, Mr. Keltie took from the shelves several Russian books, asking me to review them for Nature. I looked at the books, and, to my embarrassment, saw that they were my own works on the ‘Glacial Period’ and the ‘Orography of Asia’ (14)
.
Kropotkin confessed that he could not comply with this request and admitted the works were his own. His cover was blown and the prince retired from Nature. He went on to edit the British anarchist magazine Freedom, the motto of which remains a tribute to his politics—and his evolutionary theory: "Anarchists work towards a society of mutual aid and voluntary co-operation (15)
." In his Memoirs of a Revolutionist (1899), the Prince complained that the Darwinian struggle for existence had been misinterpreted in the biological as well as the social realm. He cried that "there is no infamy in civilized society, or in the relations of the whites towards the so-called lower races that has not been excused by the Darwinian ’struggle for existence’ (16)
."
Kropotkin—who would have been thrilled by that Airbus on the Hudson—was the first to draw attention to "mutualism" in animal behavior, a notion based on his field observations in Siberia. For him the rabbit was the very model of the social animal; its persistence—and capacity for mass production—was an argument against the dog-eat-dog world of popular (social) Darwinism.
The rabbit, he told his friend Ford Madox Ford, stood out against the fiercer aspects of selection. Defenseless and adapted for nothing in particular, it had outlived "the pterodactyl, the Hyrcanian tiger and the lion of Numidia (17)
." One wonders how he would have described those Canada geese that brought down the Airbus. He’d probably bet that the Canada goose will go on to outlive the Airbus—and Boeing for that matter—as it has outlived the Concorde, the Lockheed, and the DC 3.
Anticipating E. O. Wilson, Kropotkin proposed mutual aid as a force in natural selection which ensured that group survival need not depend a Hobbesian struggle between the weak and the strong. The Prince was neither a fan of intelligent design, nor an eco-sentimentalist: if mutual aid gave a species selective advantage, it had nothing to do with "love:"
It is not love, and not even sympathy (understood in its proper sense) which induces a herd of ruminants or of horses to form a ring in order to resist an attack of wolves; not love which induces wolves to form a pack for hunting; not love which induces kittens or lambs to play, or a dozen of species of young birds to spend their days together in the autumn; and it is neither love nor personal sympathy which induces many thousand fallow-deer scattered over a territory as large as France to form into a score of separate herds, all marching towards a given spot, in order to cross there a river. It is a feeling infinitely wider than love or personal sympathy—an instinct that has been slowly developed among animals and men in the course of an extremely long evolution, and which has taught animals and men alike the force they can borrow from the practice of mutual aid and support, and the joys they can find in social life. (18)
H.W. Bates, the father of behavioral genetics, called Kropotkin the truest Darwinist: mutual aid was a law of nature on a par with Darwin’s "group selection (16)
." But in those days before gene and DNA, neither Kropotkin nor Darwin had a clue as to the biological underpinnings of fitness or natural selection. How could generations of wild horses know exactly how many of them were needed to form a circle against wolves? How exactly did an "extremely long evolution" work out the optimum number of Canada geese required to fly in almost radar-perfect V-formation (19)
? Nowadays we turn to molecular and behavioral genetics for answers to such questions, some of which will likely be based on what we’ve learned of "quorum sensing" in microbes.
THE VIBRIO, THE SQUID, AND THE QUORUM
"Quorum sensing" was introduced in 1994 by Fuqua et al. to explain mutualism between a bioluminescent marine bacterium, Vibrio fischeri and the Hawaiian bobtail squid, Euprymna scolopes (4)
. Both benefit from cohabitation: the bacteria are nourished by nutrients from the squid and the squid gains a unique mating advantage from the vibrio. From early in their development, the squid take up the vibrios which become concentrated in light organs distributed along the body of the cephalopod (20)
. When a sufficient number of vibrios accumulate in these organs, the colony senses that it’s time to generate light by turning on luciferase genes:
... certain bacterial behaviors can be performed efficiently only by a sufficiently large population of bacteria. We describe this minimum behavioral unit as a quorum of bacteria (4)
Mutualism between vibrio and squid serves to generate what J. W. (Woody) Hastings of Harvard and the MBL has called "Light to Hide By (21)
." The bobtail squid perform their habitual mating rituals at the ocean surface on moonlit nights, but the down-dwelling light makes their amorous silhouettes visible to predators from below. Microbial luminescence to the rescue! As the vibrios set the light organs of the squid aglitter, their undersides become invisible from below (22)
. "La mer est le ciel des poissons," as Cocteau had it.
Vibrios know that there are enough of them to light up the sky by means of quorum-sensing, (QS) molecules. These were first identified as members of an N-acyl homoserine lactone (AHL) family, but further studies of both gram-positive and gram-negative bacteria found that a vast number of microbes secrete a variety of QS molecules. By now, not only AHLs, but also 2-alkyl-4(1H)-quinolones (AHQs), cyclic di-peptides, autoinducer-2 (AI-2) and small modified peptides have been identified as signals of microbial mutual aid (23
, 24)
. As might be expected in our new RNA world, Bonnie Bassler at Princeton has recently shown that a small RNA chaperone protein (Hfq), acting with multiple small regulatory RNAs (sRNAs) functions as "an ultrasensitive regulatory switch that controls the critical transition into and out of quorum sensing mode (25)
."
Quorum-sensing molecules launch signaling cascades that cross bacterial species, cut across kingdoms, and can serve both benign and pathogenic functions in human disease. Quorum sensing and its extension, the formation of biofilms, have been used to explain human ailments that range from systemic sepsis, to cystic fibrosis, sinusitis, airway infections, and even gum disease. Interference with quorum sensing is therefore the next logical step on the way to new antimicrobials (3
, 23)
. Bassler and Losick pointed out that studies of microbial quorum sensing have revealed a new world of "long- and short-range chemical signaling channels; one-way, two-way, and multi-way communication; contact-mediated and contact-inhibited signaling; and the use and spread of misinformation or, more dramatically, even deadly information (25)
. They could have been describing signals that did—and mercifully didn’t—fill the airways on January 15 when that Airbus splashed down in the Hudson.
A final note. On February 9, 2009, Mayor Bloomberg presented keys to New York City to Captain Sullenberger and his crew, who in turn paid tribute to all those, including Captain Brittany Cantazaro, who plucked crew and passengers from the icy Hudson—a story of mutual aid that would have made Kropotkin proud. On April 3, 2009, Bonnie Bassler was awarded the prestigious Wiley Prize at Rockefeller University for her "pioneering investigations into quorum sensing, a mechanism that allows bacteria to ’talk’ to one another with chemical languages (26)
." Margaret Fuller would have been proud—not only of her sea captain.
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ACKNOWLEDGMENTS
Margaret Fuller image notes: Southworth and Hawes, American, 19th Century; After: John Plumbe, American (born in Wales), 1809–1857; Margaret Fuller, 1850–55; Photograph, daguerreotype; Plate: 10.8 x 8.3 cm (4
x 3 in.); Museum of Fine Arts, Boston; Gift of Edward Southworth Hawes in memory of his father Josiah Johnson Hawes, 43.1412.
FOOTNOTES
The opinions expressed in editorials, essays, letters to the editor, and other articles comprising the Up Front section are those of the authors and do not necessarily reflect the opinions of FASEB or its constituent societies. The FASEB Journal welcomes all points of view and many voices. We look forward to hearing these in the form of op-ed pieces and/or letters from its readers addressed to journals{at}faseb.org.
REFERENCES
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