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The following passage is taken from an article about tiny organisms called archaea (© 2009 Science Daily)

  1. It’s not every day you find
  2. clues to the planet’s inner
  3. workings in aquarium scum.
  4. But that’s what happened a
  5. few years ago when
  6. University of Washington
  7. (UW) researchers cultured
  8. a tiny organism from the
  9. bottom of a Seattle Aquarium
  10. tank and found it can digest
  11. ammonia, a key environmental
  12. function. New results show
  13. this minute organism and its
  14. brethren play a more central
  15. role in the planet’s ecology
  16. than previously suspected.
  17. The findings show that these
  18. microorganisms, members of
  19. ancient lineage called archaea,
  20. beat out all other marine life
  21. in the race for ammonia.
  22. Ecologists now assume that
  23. ammonia in the upper ocean
  24. will first be gobbled up by
  25. phytoplankton to make new
  26. cells, leaving very little
  27. ammonia for microbes to turn
  28. into nitrate.
  29. Ammonia is a waste product
  30. that can be toxic to animals.
  31. But plants, including
  32. phytoplankton, prize ammonia
  33. as the most energy-efficient
  34. way to build new cells. Archaea
  35. can scavenge nitrogen-
  36. containing ammonia in the
  37. most barren environments of
  38. the deep sea, solving a long-
  39. running mystery of how the
  40. microorganisms can survive
  41. in that environment. Archaea
  42. therefore not only play a role,
  43. but are central to the planetary
  44. nitrogen cycles on which all
  45. life depends.
  46. In the tree of life, archaea
  47. occupy their own branch.
  48. Archaea were discovered only
  49. about 30 years ago and were
  50. first thought to exist only in
  51. extreme environments, such
  52. as hot springs or hydrothermal
  53. vents. They are now known to
  54. be more widespread. In the
  55. early 1990s scientists
  56. collecting seawater found
  57. strands of genetic material
  58. that suggested at least 20
  59. percent of the ocean’s
  60. microbes are archaea, and
  61. circumstantial evidence
  62. suggested they might live off
  63. ammonia.
  64. The microbe is likely
  65. ubiquitous on land and in the
  66. seas, and new experiments
  67. show that the organism can
  68. survive on a mere whiff of
  69. ammonia – 10 nanomolar
  70. concentration, equivalent to
  71. a teaspoon of ammonia salt
  72. in 10 million gallons of water.
  73. In the deep ocean there is no
  74. light and little carbon, so this
  75. trace amount of ammonia is
  76. the organism’s only source of
  77. energy.
  78. These archaea can grow at the
  79. vanishingly low concentrations
  80. of ammonia found in the
  81. ocean,” says David Stahl, a
  82. UW professor and member
  83. of the research team. “Until
  84. we made the measurements,
  85. no one thought it would be
  86. possible that an organism
  87. could live on these trace
  88. amounts of ammonia as a
  89. primary energy source.”
  90. That finding has important
  91. implications for ocean
  92. ecosystems. Scientists knew
  93. that something was turning
  94. ammonia into nitrate in the
  95. deep ocean, but could not
  96. fathom what organism
  97. might be responsible. Now it
  98. appears archaea are those
  99. mysterious organisms.
  100. And in the upper ocean
  101. waters, it appears that archaea
  102. can out-compete
  103. phytoplankton for ammonia.
  104. The same may be true in soil
  105. environments. The archaea
  106. in question are small even by
  107. the standards of single-celled
  108. organisms. At 0.2
  109. micrometers across, about 8
  110. millionths of an inch, the only
  111. life forms smaller are viruses.
  112. Researchers speculate that
  113. archaea’s size could explain
  114. how they are able to survive
  115. on such a scant energy supply.
  116. A better understanding of
  117. archaea’s lifestyle and role in
  118. nitrogen cycles not only would
  119. rewrite ecology textbooks. It
  120. could also have practical
  121. applications, such as devising
  122. natural ways to boost a soil’s
  123. nitrogen content without
  124. needing to use chemical
  125. fertilizers, or designing sewage
  126. treatment plants that employ
  127. microbes to remove
  128. nitrogenous waste more
  129. efficiently, or understanding
  130. which microbes produce
  131. global-warming gases such
  132. as nitrous oxide.
  133. The new findings will also
  134. affect the equations used in
  135. global climate models.
  136. Computer models use global
  137. cycles of nitrogen and other
  138. chemicals to estimate how
  139. much carbon dioxide the
  140. oceans will absorb and
  141. ultimately sink to the
  142. bottom of the sea. The
  143. findings also suggest that
  144. most of the nitrate in the
  145. surface water comes from
  146. recycling of biomass, and
  147. not from the deep water as
  148. currently assumed. The new
  149. data suggests, however, that
  150. the carbon pump is weaker
  151. than currently assumed, so
  152. current climate models may
  153. overestimate how much
  154. carbon can be absorbed
  155. by the oceans.