[Nitrogen-fixing activity in peat soils from a raised bog].
The nitrogenase (acetylene reductase) activity in monolithic and minced peat samples was found to be low, no more than 0.014-0.022 mg N/(kg h). Incorporation of the 15N2 isotope into organic compounds of peat soil was from 2.71-8.13 mg N/kg over 15 days. The nitrogen-fixing activity was the highest in a 10-20 cm layer of soil and much lower in the upper (under green moss) and deeper (20-30 cm) layers. The addition of glucose to soil samples stimulated nitrogen fixation considerably after 18-26 h. The maximum nitrogenase activity (3.5-3.8 mg N/(kg h)) observed after 60-70 h coincided with the peak of respiratory activity. A repeated addition of glucose after its exhaustion increased nitrogenase activity without a lag period to 8.5 mg N/(kg h). Investigation of the effect of environmental factors (temperature, pH, aeration, and light intensity) on potential nitrogen-fixing activity in peat samples revealed that nitrogen fixation could proceed in a wide range of pH values (from 3.0 to 7.5) and temperatures (from 5 to 35 degrees C). The nitrogen-fixing bacteria belonging to different trophic groups were enumerated by using nitrogen-free media with pH values and mineralization levels close to those in situ. In samples of peat soil, diazotrophic methanol-utilizing bacteria prevailed (2.0-2.5 x 10(6) cells/g); the second largest group was facultatively anaerobic bacteria of the family Enterobacteriaceae.
Kravchenko
I K
IK
Institute of Microbiology, Russian Academy of Sciences, pr. 60-letiya Oktyabrya 7, k. 2, Moscow, 117312 Russia. kravchen@inmi.da.ru
Doroshenko
E V
EV
D001419:Bacteria / Q000302:isolation & purification* / Q000378:metabolism; D015169:Colony Count, Microbial; D004755:Enterobacteriaceae / Q000302:isolation & purification; D005947:Glucose; D006863:Hydrogen-Ion Concentration; D008027:Light; D000432:Methanol / Q000378:metabolism; D009586:Nitrogen Fixation; D009587:Nitrogen Isotopes; D012988:Soil Microbiology; D013696:Temperature; D013997:Time Factors
D009587:Nitrogen Isotopes; D005947:Glucose; D000432:Methanol
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