Sine Qua Non | Distributed Awareness
“Strictly by the numbers, the vast majority — estimated by many scientists at 90 percent — of the cells in what you think of as your body are actually bacteria, not human cells. In fact, most of the life on the planet is probably composed of bacteria. They have been found making a living in Cretaceous-era sediments below the bottom of the ocean and in ice-covered Antarctic lakes, inside volcanoes, miles high in the atmosphere, teeming in the oceans — and within every other life-form on Earth. In a series of recent findings, researchers describe bacteria that communicate in sophisticated ways, take concerted action, influence human physiology, alter human thinking and work together to bioengineer the environment. Emerging knowledge about bacteria suggests that the micro-biosphere is much more like a web, with information of all kinds, including genes, traveling in all directions simultaneously. Microbes also appear to take a much more active role in their own evolution than the so-called “higher” animals. If conditions are favorable, a population of bacteria can double every 20 minutes or so. The primary method most bacteria use is called “conjugation,” a process in which genetic material is transferred between two bacteria that are in contact. It’s as close as they come to sex (although, as far as we know, lacking the romance; it’s more like downloading apps from a website). In principle, every bacterium can exchange genes with every other bacterium on the planet. A side effect of this reality: The notion of separate bacterial species is somewhat shaky, although the term is still in use for lack of a better alternative. Group behavior has now been demonstrated so widely that many microbiologists view bacteria as multicellular organisms, much of whose activity — from gene swapping to swarming to biofilm construction — is mediated by a wide variety of chemical communications. Bacteria use chemicals to talk to each other and to nonbacterial cells as well. In other words, they have “social intelligence.”
In 2007, the NIH began an ambitious program called the Human Microbiome Project, which aims to take a census of all the microorganisms that normally live in and on the human body. Most of these live in the digestive tract, but researchers have also discovered unique populations adapted to the inside of the elbow and the back of the knee. Even the left and right hands have their own distinct biota, and the microbiomes of men and women differ. The import of this distribution of microorganisms is unclear, but its existence reinforces the notion that humans should start thinking of themselves as ecosystems, rather than discrete individuals. Recent research has shown that gut microbes control or influence nutrient supply to the human host, the development of mature intestinal cells and blood vessels, the stimulation and maturation of the immune system, and blood levels of lipids such as cholesterol. They are, therefore, intimately involved in the bodily functions that tend to be out of kilter in modern society: metabolism, cardiovascular processes and defense against disease. Many researchers are coming to view such diseases as manifestations of imbalance in the ecology of the microbes inhabiting the human body. If further evidence bears this out, medicine is about to undergo a profound paradigm shift, and medical treatment could regularly involve kindness to microbes. In a surgical patient being fed by an IV drip, the gut bacteria perceive their sustenance disappearing. A decline in available nutrients alarms them. And surgery triggers the release of stress compounds that bacteria also sense, Alverdy says. Chemotherapy and radiation have similar effects. When threatened, bacteria become defensive, often producing toxins that make the host even sicker. They also tend to speed up their acquisition of and purging of genes when under external selection pressure, of which antibiotics are an obvious and powerful example. Alverdy is finding success in treating patients with a strategy he calls “ecologic neutrality.” In research reported in the August 2008 Surgery, he was able to prevent P. aeruginosa from turning virulent in surgically stressed mice by dosing them with polyethylene glycol, which supplies the bacteria with phosphate, one of their primary needs. “Once they sense there’s plenty of phosphate,” he says, “they figure everybody must be happy here.” The treated mice in his experiments, unlike the controls, did not contract fatal infections. Researchers have found several reasons to believe that bacteria affect the mental health of humans. For one thing, bacteria produce some of the same types of neurotransmitters that regulate the function of the human brain. The human intestine contains a network of neurons, and the gut network routinely communicates with the brain. Gut bacteria affect that communication. “The bugs are talking to each other, and they’re talking to their host, and their host talks back,” Young says. The phrase “gut feeling” is probably, literally true. Even more intriguingly, there have long been hints that some bacteria, including Bifidobacteria commonly found in yogurt, can improve mood. A common soil microbe, Mycobacterium vaccae, has recently been found to cheer up lab mice in experiments by Christopher Lowry.
Yellowstone’s Grand Prismatic Spring’s vivid colours are the result of pigmented bacteria; the colours range from green to red, depending on the amount of chlorophyll the bacteria has, as well as the temperature of the water.
Beyond the universe of bacterial genes recently discovered in the human gut, surveys of marine microbes are producing similarly staggering numbers of genes and species. This spring, J. Craig Venter and co-authors reported that samples of seawater taken near Bermuda yielded 150 new types of bacteria and more than a million previously unknown genes — this in an area of open ocean thought to be low in nutrients and sparsely populated by microorganisms. R. John Parkes studies microbes found in core samples collected by the Ocean Drilling Program from rocks deep below the ocean floor. “For a long time, these deep sediments were thought to be devoid of any life at all,” he says. There’s life down there, all right, but talk about slow metabolism: When Parke analyzed 4.7 million-year-old organic sediment in the Mediterranean, he estimated the average time it took for resident microbes to reproduce by cell division at 120,000 years. And he reported finding living bacteria just over a mile below the seafloor, in sediments 111 million years old and at temperatures of 140 to 212 degrees Fahrenheit. But wherever they live, bacteria can take most of the credit for bringing planetary geology into the service of life. They started working on these processes promptly upon their first emergence, perhaps as early as a mere billion years into Earth’s 4.5-billion-year history. Both the energy-releasing chemical reactions and the assembly of complex organic molecules necessary for life are “an emergent property of microbial life on a planetary scale.” In fact, Falkowski wrote, the genes that enable these processes today “may have been distributed across a common global gene pool, before cellular differentiation and vertical genetic transmission evolved as we know it today.” In other words, bacteria are supreme code monkeys that probably perfected the packages of genes and the regulation necessary to produce just about every form of life, trading genetic information among themselves long before there was anything resembling a eukaryotic cell, let alone the masters of the universe that humans believe humans to be. “They don’t waste things. They’re very efficient, very clever. They keep it simple but very elegant and sophisticated.” Giovannoni stops short of claiming that bacteria are actually thinking. But the litany of bacterial talents does nibble at conventional assumptions about thinking: Bacteria can distinguish “self” from “other,” and between their relatives and strangers; they can sense how big a space they’re in; they can move as a unit; they can produce a wide variety of signaling compounds, including at least one human neurotransmitter; they can also engage in numerous mutually beneficial relationships with their host’s cells. Even more impressive, some bacteria, such as Myxococcus xanthus, practice predation in packs, swarming as a group over prey microbes such as E. coli and dissolving their cell walls.
Marc van Duijn and colleagues point out that the presence of “the basic processes of cognition, such as perception, memory and action” in bacteria can now be “plausibly defended.” And bacteria that have antibiotic-resistance genes advertise the fact, attracting other bacteria shopping for those genes; the latter then emit pheromones to signal their willingness to close the deal. These phenomena, Herbert Levine’s group argues, reveal a capacity for language long considered unique to humans. But this raises the question: Is some nonhuman software organizing the teamwork of all those nonhuman semi-smart robots, aka bacteria? For this would be the truly radical argument: that bacteria — demonstrably integrated deeply and broadly into the entire planet, shaping its geochemistry, creating substrates and chemical processes that support the development of complex organic molecules, regulating the cycling of energy and nutrients both in “higher” organisms and their environments — constitute a kind of distributed awareness encompassing the whole planet. That not only are bacteria in a given local environment busy texting each other like mad, but the entire planet may consist of a giant Microbial World Wide Web. In a more down-to-earth assessment, it is clear that bacteria are not what the general run of humans thought they were, and neither are humans. Bacteria are the sine qua non for life, and the architects of the complexity humans claim for a throne. The grand story of human exceptionalism — the idea that humans are separate from and superior to everything else in the biosphere — has taken a terminal blow from the new knowledge about bacteria. Whether humanity decides to sanctify them in some way or merely admire them and learn what they’re really doing, there’s no going back. And if there’s any hope of rebalancing the chemistry of a biosphere deranged in two short centuries by humans, it very likely lies in peaceful coexistence with the seemingly brilliant, deceptively simple life-forms comprising the domain Bacteria.”