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toria bennett told me。
in the 1920s two scientists at the university of chicago； edson bastin and frank greer；announced that they had isolated from oil wells strains of bacteria that had been living at depths of two thousand feet。 the notion was dismissed as fundamentally preposterous鈥攖herewas nothing to live on at two thousand feet鈥攁nd for fifty years it was assumed that theirsamples had been contaminated with surface microbes。 we now know that there are a lot ofmicrobes living deep within the earth； many of which have nothing at all to do with theorganic world。 they eat rocks or； rather； the stuff that鈥檚 in rocks鈥攊ron； sulfur； manganese；and so on。 and they breathe odd things too鈥攊ron； chromium； cobalt； even uranium。 suchprocesses may be instrumental in concentrating gold； copper； and other precious metals； andpossibly deposits of oil and natural gas。 it has even been suggested that their tireless nibblingscreated the earth鈥檚 crust。
some scientists now think that there could be as much as 100 trillion tons of bacteria livingbeneath our feet in what are known as subsurface lithoautotrophic microbial ecosystems鈥攕lime for short。 thomas gold of cornell has estimated that if you took all the bacteria out ofthe earth鈥檚 interior and dumped it on the surface； it would cover the planet to a depth of fivefeet。 if the estimates are correct； there could be more life under the earth than on top of it。
at depth microbes shrink in size and bee extremely sluggish。 the liveliest of them maydivide no more than once a century； some no more than perhaps once in five hundred years。
as the economist has put it： 鈥渢he key to long life； it seems； is not to do too much。鈥潯henthings are really tough； bacteria are prepared to shut down all systems and wait for bettertimes。 in 1997 scientists successfully activated some anthrax spores that had lain dormant foreighty years in a museum display in trondheim； norway。 other microorganisms have leaptback to life after being released from a 118…year…old can of meat and a 166…year…old bottle ofbeer。 in 1996； scientists at the russian academy of science claimed to have revived bacteriafrozen in siberian permafrost for three million years。 but the record claim for durability so faris one made by russell vreeland and colleagues at west chester university in pennsylvaniain 2000； when they announced that they had resuscitated 250…million…year…old bacteria calledbacillus permians that had been trapped in salt deposits two thousand feet underground incarlsbad； new mexico。 if so； this microbe is older than the continents。
the report met with some understandable dubiousness。 many biochemists maintained thatover such a span the microbe鈥檚 ponents would have bee uselessly degraded unless thebacterium roused itself from time to time。 however； if the bacterium did stir occasionallythere was no plausible internal source of energy that could have lasted so long。 the moredoubtful scientists suggested that the sample may have been contaminated； if not during itsretrieval then perhaps while still buried。 in 2001； a team from tel aviv university argued thatb。 permians were almost identical to a strain of modern bacteria； bacillus marismortui； foundin the dead sea。 only two of its genetic sequences differed； and then only slightly。
鈥渁re we to believe；鈥潯he israeli researchers wrote； 鈥渢hat in 250 million years b。 permianshas accumulated the same amount of genetic differences that could be achieved in just 3鈥�7days in the laboratory？鈥潯n reply； vreeland suggested that 鈥渂acteria evolve faster in the labthan they do in the wild。鈥�
maybe。
it is a remarkable fact that well into the space age； most school textbooks divided the worldof the living into just two categories鈥攑lant and animal。 microorganisms hardly featured。
amoebas and similar single…celled organisms were treated as proto…animals and algae as proto…plants。 bacteria were usually lumped in with plants； too； even though everyone knewthey didn鈥檛 belong there。 as far back as the late nineteenth century the german naturalisternst haeckel had suggested that bacteria deserved to be placed in a separate kingdom； whichhe called monera； but the idea didn鈥檛 begin to catch on among biologists until the 1960s andthen only among some of them。 （i note that my trusty american heritage desk dictionaryfrom 1969 doesn鈥檛 recognize the term。）many organisms in the visible world were also poorly served by the traditional division。
fungi； the group that includes mushrooms； molds； mildews； yeasts； and puffballs； were nearlyalways treated as botanical objects； though in fact almost nothing about them鈥攈ow theyreproduce and respire； how they build themselves鈥攎atches anything in the plant world。
structurally they have more in mon with animals in that they build their cells from chitin；a material that gives them their distinctive texture。 the same substance is used to make theshells of insects and the claws of mammals； though it isn鈥檛 nearly so tasty in a stag beetle as ina portobello mushroom。 above all； unlike all plants； fungi don鈥檛 photosynthesize； so theyhave no chlorophyll and thus are not green。 instead they grow directly on their food source；which can be almost anything。 fungi will eat the sulfur off a concrete wall or the decayingmatter between your toes鈥攖wo things no plant will do。 almost the only plantlike quality theyhave is that they root。
even less fortably susceptible to categorization was the peculiar group of organismsformally called myxomycetes but more monly known as slime molds。 the name no doubthas much to do with their obscurity。 an appellation that sounded a little more dynamic鈥斺�渁mbulant self…activating protoplasm；鈥潯ay鈥攁nd less like the stuff you find when you reachdeep into a clogged drain would almost certainly have earned these extraordinary entities amore immediate share of the attention they deserve； for slime molds are； make no mistake；among the most interesting organisms in nature。 when times are good； they exist as one…celled individuals； much like amoebas。 but when conditions grow tough； they crawl to acentral gathering place and bee； almost miraculously； a slug。 the slug is not a thing ofbeauty and it doesn鈥檛 go terribly far鈥攗sually just from the bottom of a pile of leaf litter to thetop； where it is in a slightly more exposed position鈥攂ut for millions of years this may wellhave been the niftiest trick in the universe。
and it doesn鈥檛 stop there。 having hauled itself up to a more favorable locale； the slimemold transforms itself yet again； taking on the form of a plant。 by some curious orderlyprocess the cells reconfigure； like the members of a tiny marching band； to make a stalk atopof which forms a bulb known as a fruiting body。 inside the fruiting body are millions ofspores that； at the appropriate moment； are released to the wind to blow away and beesingle…celled organisms that can start the process again。
for years slime molds were claimed as protozoa by zoologists and as fungi by mycologists；though most people could see they didn鈥檛 really belong anywhere。 when genetic testingarrived； people in lab coats were surprised to find that slime molds were so distinctive andpeculiar that they weren鈥檛 directly related to anything else in nature； and sometimes not evento each other。
in 1969； in an attempt to bring some order to the growing inadequacies of classification； anecologist from cornell university named r。 h。 whittaker unveiled in the journalscience aproposal to divide life into five principal branches鈥攌ingdoms； as they are known鈥攃alledanimalia； plantae； fungi； protista； and monera。 protista； was a modification of an earlier term； protoctista； which had been suggested a century earlier by a scottish biologist namedjohn hogg； and was meant to describe any organisms that were neither plant nor animal。
though whittaker鈥檚 new scheme was a great improvement； protista remained ill defined。
some taxonomists reserved it for large unicellular organisms鈥攖he eukaryotes鈥攂ut otherstreated it as the kind of odd sock drawer of biology； putting into it anything that didn鈥檛 fitanywhere else。 it included （depending on which text you consulted） slime molds； amoebas；