It’S PROBABLY NOt a good idea to take too personal an i in your microbes. LouisPasteur, t Frend bacteriologist, became so preoccupied    ook to peering critically at every dis tpresumably did not ations to dinner.

        In fact, t in trying to eria, for t ceive. If you are in good    about orillion bacteria grazing on your fles a imeter of skin. to dineoff ten billion or so flakes of skin you sasty oils and fortifyingminerals t seep out from every pore and fissure. You are for timate food court,ant mobility they giveyou B.O.

        And t teria t in your skin. trillions more tucked a and nasal passages, ging to your eetive system alone is to more trillion microbes, of at least four ypes. Some deal arctack oteria. A surprising number, like tous iinal spiroces, ectable fun at all. t seem to like tobe s of about 10 quadrillion cells, but about 100quadrillion bacterial cells. t, a big part of us. From teria’s point ofvie of them.

        Because ilize antibiotiddisiants, it is easy to vince ourselves t o tence. Don’t you believe it. Bacteria may not build cities or eresting social lives,but t, and    onlybecause to be.

        Bacteria, never fet, got along for billions of years    us. e couldn’t survive a day tes and make t tmunc. ter and keep our soils productive. Bacteriasyntamins in ut, vert t into useful sugars andpolysacco    slip do.

        e depend totally on bacteria to pluitrogen from t it into usefulides and amino acids for us. It is a prodigious and gratifyi. As Margulis andSagan o do trially (as urers must terials to 500 degrees tigrade and squeeze to timesnormal pressures. Bacteria do it all time    fuss, and t trogen tioprovide us o keep tmospable. Microbes, including teria, supply ter part of t’s breathable oxygen.

        Algae and otiny anisms bubbling a about 150 billion kilos oftuff every year.

        And tic among tionien minutes; Clostridium perfringens, ttle anism t causesgangrene,    reprodu nine minutes. At suce, a single bacterium could ticallyproduce more offspring in tons in tesupply of nutrients, a single bacterial cell    gee 280,000 billion individuals in a singleday,” acc to t and Nobel laureate    de Duve. In t about manage a single division.

        About once every million divisions, tant. Usually tant—c just occasionally terium isendoal advantage, sucy to elude or stack ofantibiotics. ity to evolve rapidly goes anotage. Bacteriasion. Any bacterium    take pieces of geic g from any other.

        Essentially, as Margulis and Sagan put it, all bacteria sive c occurs in one area of terial universe    spread to any ot’srato an io get tic g to sprout    means t from a geic point of vieeria iny, dispersed, but invincible.

        t anyt givettle moisture—as ed from not als in . Stists in Australia found microbes knoivorans t livedin—indeed, could not live —trations of sulfuric acid strong enougo dissolvemetal. A species called Micrococcus radiope tanksof nuclear react itself on plutonium and eriabreak do at all.

        ts and lakes of caustic soda, deep insiderocks, at ttom of ter in tarctica, and seven miles doimes greater t t to being squasyjumbo jets. Some of to be practically iructible. Deinococcus radiodurans is,acc to t , “almost immuo radioactivity.” Blast its DNA ion,and tely reform “like ttling limbs of an undead creature from ahorror movie.”

        Per extraordinary survival yet found    of a Streptococcus bacteriumt    ood on two years.

        In s, ts in    prepared to live. “t s so    t tually startto melt, teria even toria Beold me.

        In tists at ty of    and Frank Greer,annou ted from oil rains of bacteria t dept. tion ally preposterous—to live on at t—and for fifty years it    tami ofmicrobes living deep    all to do    rocks or, ratuff t’s in rocks—iron, sulfur, manganese,and so on. And too—iron, c, even uranium. Sucrumental in trating gold, copper, and otals, andpossibly deposits of oil and natural gas. It ed t tireless nibblingscreated t.

        Some stists no trillion tons of bacteria livi in otropems—SLiME for s. timated t if you took all teria out ofterior and dumped it on t    to a dept. If timates are correct, top of it.

        At deptremely sluggis of tury, some no more than perhaps on five hundred years.

        As t    it: “to long life, it seems, is not to do too mucougeria are prepared to s doems and    for bettertimes. In 1997 stists successfully activated some ant    frondback to life after being released from a 118-year-old eat and a 166-year-old bottle ofbeer. In 1996, stists at to eriafrozen in Siberian permafrost for t ty so faris one made by Russell Vreeland and colleagues at est Cer Uy in Pennsylvaniain 2000, ated 250-million-year-old bacteria calledBacillus permians t rapped in salt deposits t underground inCarlsbad, s.

        t met andable dubiousness. Many biocs maintaiover sucs self from time to time. erium did stir occasionallyternal source of energy t could ed so long. tful stists suggested t taminated, if not during itsretrieval till buried. In 2001, a team from tel Aviv Uy argued tB. permians    identical to a strain of modern bacteria, Bacillus marismortui, foundin ts geic sequences differed, and tly.

        “Are o believe,” te, “t in 250 million years B. permia of geic differe could be ac 3–7days in tory?” In reply, Vreeland suggested t “bacteria evolve faster in the wild.”

        Maybe.

        It is a remarkable fact t o t scextbooks divided to just tegories—plant and animal. Micranisms ured.

        Amoebas and similar single-celled anisms reated as proto-animals and algae asproto-plants. Bacteria s, too, even t belong te eentury turalistEr bacteria deserved to be placed in a separate kingdom,    begin to cattil te t my trusty Ameri age desk diaryfrom 1969 doesn’t reize term.)Many anisms in traditional division.

        Fungi, t includes muss, and puffballs, reated as botanical objects, t almost not tc world.

        Structurally t tin,a material t gives tinctive texture. tance is used to make ts and t isn’t nearly so tasty in a stag beetle as ina Portobello muss, fungi don’t posynt green. Ily on t anyt te ter betoes—t    tlike quality t t.

        Even less fortably susceptible to categorization es but more only knoo do y. An appellation t sounded a little more dynamic—“ambulant self-activating protoplasm,” say—and less like tuff you find    certainly raordinary entities amore immediate stention take,among t iing anisms in nature. imes are good, t as one-celled individuals, muc ougo atral gat miraculously, a slug. t a ty and it doesn’t go terribly far—usually just from ttom of a pile of leaf litter to top,    for millions of years tiest tri the universe.

        And it doesn’t stop tself up to a more favorable locale, transforms itself yet again, taking on t. By some curious orderlyprocess tiny marake a stalk atopof ing body are millions ofspores t, at te moment, are released to to blo    start the process again.

        For years slime molds ozoa by zoologists and as fungi by mycologists,t people could see t really belong aingarrived, people in lab coats o find t slime molds inctive andpeculiar t t directly related to anyture, and sometimes o eacher.

        In 1969, in an attempt t some order to tion, anecologist from ell Uy named R. taker unveiled in to divide life into five principal brancae, Fungi, Protista, and Monera. Protista, ion of an earlierterm, Protoctista, ury earlier by a Scottis namedJo to describe any anisms t    nor animal.

        ttaker’s ne, Protista remained ill defined.

        Some taxonomists reserved it for large unicellular anisms—tes—but otreated it as tting into it anyt didn’t fitany you sulted) slime molds, amoebas,and even sea tained as many as 200,000different species anism all told. t’s a lot of odd socks.

        Ironically, just as taker’s five-kingdom classification o find its o textbooks, a retiring academic at ty of Illinois     o do so—lystudyiic sequences in bacteria. In takingprocess. ork on a single bacterium could easily e a year. At t time, acc tooese, only about 500 species of bacteria    ten times t, t is stillfar s of tedanisms whe annals of biology.

        It isn’t simple indiffere keeps total loeria    be exasperatingly difficultto isolate and study. Only about 1 pert ure. sidering able ture, it is an odd fact t t to ri dis    liet to bloom. Any bacterium t tion exceptional, a exclusively, tudied bymicrobiologists. It    animals from visiting zoos.”

        Genes, o approac tal divisions in ted. A lot of little anisms t looked like bacteria and beeria ually sometoget eria a long time ago. oese called teria, later seoarchaea.

        It    ttributes t distinguiseria are not t t a biologist. tly differences in tidogly. But in practice t from bacteria ted division of life, so fualt it stood above t tree of Life, as it isratially known.

        In 1976, artled t least ttle bit of it t tention—byredraree of life to incorporate not five main divisions, but ty-tegories—Bacteria, Arcimesspelled Eucarya)—which he called domains.

        oese’s ake torm. Some dismissed too ed to igo Frances As, “felt bitterly disappointed.” But slocs. Botanists and zoologists s virtues.

        It’s not o see edto a feermost branicellular beings.

        “t up to classify in terms of gross morpies anddifferences,” oese told an intervieerms of molecularsequence is a bit o s see a difference like it. And so ted raditional five-kingdom division—an arra oese called “not very useful” in s and “positively misleading” muc of time. “Biology, like p,” oese e, “o a level erest aions often ot be perceived t observation.”

        In 1998 t and a    Ernst Mayr ( time of my ing is nearing one ill going strong) stirredt furt t two prime divisions of life—“empires”

        ional Academy of Sces,Mayr said t oese’s findiing but ultimately misguided, noting t“oese    trained as a biologist and quite naturally does not ensivefamiliarity ion,”     e to saying of anot    kno.

        ticisms are too teeed extensive airing ic sexuality, ion, and troversial interpretationsof terium trop else—butessentially    oese’s arra unbalaree of life. terialrealm, Mayr notes, sists of no more to be found—“but .” By trast, tic realm—t is, ted anisms ed cells, like us—numbers already in terial anisms in a siegory,Prokaryota,    anothe living world.”

        tin beteriaand gram-positive bacteria clearly ter of moment for most of us, but it is ea its neigs. Ifoese’s eac is t life really is various and t most oft variety is small, unicellular, and unfamiliar. It is a natural o tion as a long cs, of a never-ending advaoy—in a oter ourselves. Most of ty inevolution    flukes—an iing side brancy-ts, animals, and fungi—are largeenougo be seen by tain species t are microscopic.

        Indeed, acc to oese, if you totaled up all t—every livingts included—microbes    for at least 80 pert of all to t ime.

        So    some point in your life, do microbes so often    to us?    possible satisfa could to a microbe in , after all, is oprovide long-term ality.

        to begin    is    most micranisms are ral or evenbeneficial to    rampantly iious anism oerium called olbac     all—or, e to t, any otebrates—but if you are a s fly, it    make you    one microbe in a to National Geograp some of t t is quite enougly benign, microbes are still tern ence.

        Making a    uns for toms of an illnessoften o spread ting, sneezing, and diarr metting out of one    and into position for anot effective strategy of all is toenlist ty. Iious anisms love mosquitoes because to’s sting delivers tly to a bloodstream raigo im’s defense mec is, and a ed but often rapaaladies—begin o bite. It is afortunate fluke for us t , isn’t among t least not yet. Any o sucks up on its travels is dissolved by to’s oabolism.    tates its rouble.

        It is a mistake, o sider tter too carefully from tion of logicbecause micranisms clearly are not calculatiies. t care oyou any more t distress you cause . time your tinuing o a pat kills you too e you before t t sometimes ory,Jared Diamond notes, is full of diseases t “once caused terrifying epidemid teriously as tes t but mercifully traEnglising siess, ens of t, before burning itself out. too muc a good tianism.

        A great deal of siess arises not because of o you but rying to do to ts quest to rid tem sometimes destroys cells or damages critical tissues, so often    t your oting sick is a sensible respoo iion. Sick people retire to t to ty. Resting also frees more of toattend to tion.

        Because t tential to    you, your body s of different varieties of defensive en million types in all, eaco identify aroy a particular sort of invader. It to maintain ten million separate standing armies, so eacy of s on active duty. ious agent—igen—invades,relevant scouts identify ttacker and put out a call for reinforts of t type.

        uring to feel c ofrecovery begins o a.

        e cells are merciless and    patoavoid extin, attackers al strategies. Eitrike quicklyand move on to a neious illnesses like flu, or t te cells fail to spot t iced in to a.

        One of ts of iion is t microbes t normally do no    allsometimes get into ts of the words of Dr.

        Bryan Marsious diseases specialist at Dartmoutcer inLebanon, Nes    are normally benign in t get into ots of tream, for instand cause terrible havoc.”

        t, most out-of-trol bacterial disorder of t is a disease calledizing fasciitis in ially eat tim from t, devinternal tissue and leavis often e in ively mild plaints—a skin rasypically—but ticallydeteriorate.    is often found t they are simply being ed.

        treatment is ting out every bit ofied area. Seventy pert of victims die; many of t are left terribly disfigured. tion is a mundane family of bacteria called Group A Streptococcus, . Very occasionally, for reasons unknet t and into t devastating ely resistant to antibiotics. About ated States, and no one    say t it    get worse.

        Precisely tis. At least 10 pert of young adults, andper of teenagers, carry terium, but it lives quite. Just occasionally—in about one young person in a    gets into tream and makes t cases,deat and dead by evening,” says Marsh.

        e    so profligate    tibiotics. Remarkably, by oimate some 70 pert of tibiotics used in to farm animals, often routinely in stockfeed, simply to promote gro iion. Sus givebacteria every opportunity to evolve a resistao t is an opportunity t tically seized.

        In 1952, penicillin ive against all strains of staperia, to sut t by te, felt fidentenougo declare: “time o close tious diseases. e    iion iates.” Even as    of trains y to penicillin. Soorains, called Metant Stapo sals. Only oype of antibiotic, vany, remained effective against it, but in 1997a al in tokyo reported train t could resist even t. it o six otals. All over, toals alone, some fourteen tions ted, given a cibiotics t people ake every day for tidepressants tpeople ake every day forever, drug panies not surprisingly opt for tter.

        Altibiotics oug, tical industry given us airely neibiotice the 1970s.

        Our carelessness is all t many ots maybe bacterial in in. toriern Australia, found t many stomaacerium called er pylori. Eveed,tion    more ted. America’s National Institutes of ance, didn’t officially endorse til 1994. “    old a reporter from Forbes in 1999.

        Sierial po inall kinds of ot disease, astis, multiple sclerosis, several typesof mental disorders, many cers, even, it ed (inSo less), obesity.

        t be far off ive antibiotid got oo call on.

        It may e as a slig to kno bacteria    t sick. times ied by bacteriopype of virus. A virus is a strangeand unlovely entity—“a piece of nucleic acid surrounded by bad er Medaeria, viruses aren’ttion t and    introduce to a suitable and t into busyness—into life. About five types of virus are kno us o t are most invidious to he source of AIDS.

        Viruses prosper by ic material of a living cell and using it to producemore virus. tical ma out in searvade. Not being living anisms to be very simple. Many,including en genes or feeria require severaltiny, muall to be seen ional microscope.

        It    until 1943 and tion of tron microscope t sce got its first lookat t tietury alone killed aimated 300 million people.

        ty to burst upon tartlingform and to vaniso e de sleeping siess, ims o sleep and not    great difficulty to take foo to tory, and ionssensibly—tic.

        tted to rest, t once batodeepest slumber and remain in t state for as long as t. Some    on in t notted in a state of profound apatinct voloes,” intor. In ten years tly    a didn’t get mug attention because in time an even    in ory—s across the world.

        It is sometimes called t Simes t Spanis i y-one million people infour years; ss first four mont 80 pert of Americasualties in t orld ar came not from enemy fire, but from flu. In some units tality rate was as .

        S some mutated into sometims suffered only mild symptoms, but t became gravely ill and often died.

        Some succumbed hers held on for a few days.

        Iates, t deaton in late August1918, but to all parts of try. Scertais tle good. Betumn of 1918 and spring of toll in Britain h similar numbers dead in Frand Germany.

        No one knooll, as records in ten poor, but it less timates    total as high as 100 million.

        In an attempt to devise a vae, medical auties ducted tests on volunteers at amilitary prison on Deer Island in Boston tery of tests. tests o say t. First ts ed ed lung tissue taken from tious aerosols. If till failed to succumb, ts saken from to sitopen-moutim heir faces.

        Out of—someeered, tors cy-tests. None tracted t oor, ion for t teers, all of ation, ural immunity.

        Muc tood poorly or not at all. One mystery is    eruptedsuddenly, all over, in places separated by os, mountain ranges, and ots. A virus    survive for no more tside a    body, so    appear in Madrid, Bombay, and Phe same week?

        t it ed and spread by people oms or    all. Even in normal outbreaks, about 10 pert of people    are una because ts. And because tioo be t spreaders of the disease.

        t    for tbreak’s ribution, but it still doesn’texplain    mao lay loing so explosively at moreor less time all over. Even more mysterious is t it ating topeople in t on infants and t in tbreak deaties and ties. Olderpeople may ed from resistance gained from an earlier exposure to train,but    mystery of all is . e still have no idea.

        From time to time certain strains of virus return. A disagreeable Russian virus kno againin t    in time eacime is uain. One suggestion is tviruses    unnoticed in populations    t a neion of    ty t t Swine Flu epidemicmigs head.

        And if it doesn’t, ot. New and frigime.

        Ebola, Lassa, and Marburg fevers all eo flare up and die do no one say t t quietly mutating aopportunity to burst fortastrop is no t AIDS ed. Researc terRoyal Infirmary in England discovered t a sailor reatablecauses in 1959 in fact    for    for anoty years.

        t ot gone rampant. Lassa fever,    detected until 1969, i Africa, is extremely virulent and little uood. In 1969, adoctor at a Yale Uy lab in Ne, . , more alarmingly, a tec exposure, also tracted the disease and died.

        break stopped t    t on sue alyles invite epidemics. Air travel makes it possible to spread iious agents across t    inNe medical autiesincreasingly o be acquaiy muc exists every. In 1990, a Nigerian living in Co Lassa fever on avisit to    didn’t develop symptoms until uro ted States.

        al    diagnosis and    aaking any specialprecautions iing     letious diseaseson t. Miraculously, no one else ed. e may not be so luext time.

        And on t s ’s time to return to the visibly living.
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