contamination remains the main challenge: keeping 

 the bacteria you want from mixing with all the oth- 

 er microorganisms in the environment and on your- 

 self. What has changed dramatically in recent times 

 is how the collected microorganisms are studied. Typ- 

 ically only a small fraction of the full microbial com- 

 munity grows in standard laboratory conditions. 

 Look at a diluted speck of our Alaskan soil sample 

 under a microscope, and you see a teeming world of 

 rod- and sphere-shaped cells. Yet less than 1 percent 

 of those cells take to life in a Petri dish. It could be 

 compared to throwing a party, inviting a thousand 

 people, and having only one person show his face. 

 Microbiologists refer to the bacteria that don't show 

 up in laboratories as "the uncultured majority." 



The breakthrough in the study of this major slice 

 of life came in the early 1980s, when microbiologists 

 realized that microbial DNA could be extracted and 

 read without culturing the organisms first. New mol- 

 ecular techniques for manipulating DNA have 

 launched another age of exploration and discovery of 

 the microbial world, with staggering results. It has be- 

 come routine to find novel genes and exotic strains of 

 microorganisms even in samples from rather ordinary 

 habitats. Entirely new phyla are still being 

 unearthed. In 1987 microbiologists 

 recognized about a dozen ^| 

 bacterial phyla, all of which (flfe 

 could be grown in a lab- 

 oratory dish. Today at A 



Frankia bacteria form nodules on the roots of an alder 

 plant (upper right) and supply the alder with usable nitro- 

 gen in exchange for sugar. At the microscopic level (above) 

 Frankia often grow in filaments that extend and branch out 

 at the tips; they also develop vesicles, or round structures, 

 where they process nitrogen from the air. The micrograph 

 is magnified 1,100X. 



least fifty-three phyla are known, twenty-seven only 

 through their DNA. 



In other words, like pandas that won't breed in a 

 zoo, the wild bacteria from those twenty-seven phy- 

 la have yet to be cultured in the laboratory. Perhaps 

 they need biochemical compounds produced by 

 other members of their microbial community, mak- 

 ing it impossible for them to reproduce and multi- 

 ply in pure cultures. Or perhaps the conditions in a 

 Petri dish are too rich, compared with conditions in 

 their natural habitats: A group of investigators at Ore- 

 gon State University in Corvallis recently cultured a 

 newly discovered, yet widespread, marine bacteri- 

 um by growing it in little more than seawater. 



The excavation of the enormous diversity in the 

 microbial world is redesigning the tree of life. At the 

 genetic level, plants and animals turn out to be mere 

 twigs among a dense thicket of bacteria, archaea (the 

 recently recognized third domain of life), and other 

 kinds of microscopic organisms. The genetic studies 

 are also changing the scientific understanding of the 

 basic flow of elements through the environment. 

 Microorganisms, after all, are the main gateway be- 

 tween the animate and inanimate — they can subsist 

 on sludge, rock, or even toxic waste, and thereby 

 open up a food chain. 



To explore the hidden world, microbiologists 

 have set up a network of some fifty "microbial 

 observatories," such as the Bonanza Creek 

 observatory in Alaska, to take a cen- 

 sus of microorganisms living there. 

 Scattered around the globe in a 

 range of environments, the observa- 

 tories have discovered thousands of 

 novel microbial types, and even new 

 biochemical pathways. 

 The Bonanza Creek observatory is dis- 

 tinguished by the unusual way in which local 

 bacteria obtain the element phosphorus, which in 

 turn enables the rest of the forest to grow. Work at the 

 observatory is also turning up unusual antibiotics and 

 other biochemicals produced in the cold. And this be- 

 ing Alaska, in the early years of the twenty-first cen- 

 tury, the boreal site and its samples are becoming grist 

 for the study of global-warming effects as well. 



In the language of the native people of this land, 

 the Athabascans, tanana suggests "mountain riv- 

 er." Run-off from glaciers in the Alaska Range — the 

 mountains that include North America's highest 

 peak, Denali — converges into streams that eventual- 

 ly form the Tanana. The river also carries debris from 

 the glacier-scraped mountain range: a fine silt, which 

 colors the water a concrete-dun. Word around Fair- 

 banks is that if you fall into the Tanana, you must get 



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NATURAL HISTORY April 2006 



