Plant and Soil

, Volume 51, Issue 2, pp 187–196 | Cite as

Nitrogen-fixing bacillus species from Egyptian soils: Acetylene reduction and cultural conditions

  • A. M. Abdel Wahab
  • H. M. El-Sharouny


Among 390 isolates from Egytiian soils initially grown on Brown's N-free agar, 15 facultative Bacillus isolates were able to reduce acetylene in Stanier's N-poor broth under both aerobic and anaerobic (N2 atmosphere) conditions. Some of these isolates were Gram-positive, with unswollen sporangia and thin-walled endospores. Other strains were with slightly or definitely bulged sporangia. Yeast extract (0.01%) was essential for growth stimulation and N2[C2H2] fixation by these isolates. Replacing yeast extract with 20 μg/ml (NH4)2SO4 or biotin, thiamine and amino acids (singly or in combination) resulted in stimulation of growth and N2[C2H2] fixation, though at lower rates than in yeast extract.

One isolate was able to grow and reduce C2H2 in Stanier's N-free liquid medium. Nitrogenase [C2H2] activity of the anaerobically grown and incubated cultures was greater than aerobic cultures. Addition of 0.1% CaCO3 to the culture media significantly increased and O2 partially inhibited, N2[C2H2] fixation by these Bacillus isolates.

Studies of the characteristics and N2[C2H2] fixing activities of these isolates indicate that at least some of them are new nitrogen-fixingBacillus species.

Key Words

Acetylene reduction Aerobic Anaerobic Bacillus Nitrogen fixation 


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Copyright information

© Martinus Nijhoff 1979

Authors and Affiliations

  • A. M. Abdel Wahab
    • 1
  • H. M. El-Sharouny
    • 1
  1. 1.Department of BotanyAssiut UniversityAssiutEgypt, A.R.E.

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