%0 Journal Article %A Okon, Aacov %A Houchins, Jeffrey P. %A Albrecht, Stephan L. %A Burris, R. H. %T Growth of Spirillum Lipoferum At Constant Partial Pressures of Oxygen, and the Properties of its Nitrogenase in Cell-free Extracts %D 1977 %J Microbiology, %V 98 %N 1 %P 87-93 %@ 1465-2080 %R https://doi.org/10.1099/00221287-98-1-87 %I Microbiology Society, %X Summary: Spirillum lipoferum, an N2-fixing organism, was grown at constant concentrations of dissolved O2. When supplied with NH4 + aerobically, its doubling time was 1 h; when it fixed N2 microaerophilically, its doubling time was 5·5 to 7 h and the optimal P o2 for growth was 0·005 to 0·007 atm. At its optimal P o2 for growth on N2, S. lipofernum assimilated 8 to 10 mg nitrogen/g carbon substrate used; its efficiency was less at higher P O2 levels. Nitrogenase in cell-free extracts required Mg2+ and Mn2+, and the Fe-protein was activated by Rhodospirillum rubrum activating factor. The nitrogenase had an optimal pH of 7·1 to 7·4 and an apparent K m for acetylene of 0·0036 atm. Extracts of S. lipoferum lost their nitrogenase activity on storage at −18 °C, and activity was restored by adding purified Feprotein from other N2-fixing bacteria. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-98-1-87