@article{mbs:/content/journal/micro/10.1099/00221287-98-1-87, author = "Okon, Aacov and Houchins, Jeffrey P. and Albrecht, Stephan L. and Burris, R. H.", title = "Growth of Spirillum Lipoferum At Constant Partial Pressures of Oxygen, and the Properties of its Nitrogenase in Cell-free Extracts", journal= "Microbiology", year = "1977", volume = "98", number = "1", pages = "87-93", doi = "https://doi.org/10.1099/00221287-98-1-87", url = "https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-98-1-87", publisher = "Microbiology Society", issn = "1465-2080", type = "Journal Article", abstract = "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.", }