02324nam a2200313 a 450000100080000000500110000800800410001910000210006024500600008126000420014130000090018350000190019252015470021165000220175865000110178065000090179165000140180065000210181465000290183565000140186465000090187865300080188765300360189565300080193165300290193965300070196865300110197565300240198615649042002-06-04       1977    bl uuuu  m   00u1 u    #d1 aVARGAS, M. A. T.  aEffect of oxygen on N2 fixation by Spirillum lipoferum.  a[S.l.]: Univeristy of Wisconsinc1977  a69p.  aMaster Thesis.  aThe effect of dissolved oxygen tension (DOT) on the growth rate, growth yield, energy efficiency and cell composition of Spirillum lipoferum was evaluated in stirred batch and continuous culture at pH 6.8 and 30 oC using a growth limiting level of 0.1 electron equivalent (e eq) succinate/1 (0.83 g/1) as the C and e- donor source and N2 or NH4+ as the N source. DOT was controlled using an =2-stat with an autoclavable =2 electrode immersed in the culture, and premixed 1% and 4% =2 in N2 as the O2 supply. The apparent optimum DOT level for N2-fixing growth in batch and continuous culture, both from the standpoint of the rate of growth (minimum doubling time, td, of 4, 6 hr in b a t c h) and the efficiency of N2 fixation (26 and 28 mg N2 fixed/g succinate in batch and continuous culture, respectively), was about 0.0005 atm O2. At this optimum DOT for N2 -fixing growth, the storage organic carbon was estimated indirectly to be 5 to 26% and 2 to 14% (depending on the method of calculation of the cell dry weight as poly-B-hydroxybutyrate (PHB) for batch and continuous culture, respectively. The dissimilatory electron requirement for N2 fixation at the optimum DOT level was 33.3 and 34 e- eq succinate dissimilated/mole cell N, for batch and continuous culture, respectively. Under limiting O2 (e.g. DOT &lt&lt0.0005 atm O2), the td increased to 7.0 hr in batch culture; the storage C increased to 19 and 27 e- eq/mole cell N (about 48 and 57% PHD), whereas N2 fixation yield decreased to 18 and 15 mg N2 fixation increased........  anitrogen fixation  aoxygen  asoil  aBactéria  aBiologia do Solo  aFixação de Nitrogênio  aOxigênio  aSolo  aFBN  aFixacao biologica de nitrogenio  aNBF  aNitrogen fixing bacteria  aO2  aOxigen  aSpirillum lipoferum