The Apparent ATP Requirement for Nitrogen Fixation in Growing Klebsiella pneumoniae

Abstract

SUMMARYThe apparent ATP requirement for N, fixation in Klebsiella pneumoniae was high (the ATPIN, molar ratio was 29 when estimated in anaerobic glucose-limited chemostat cultures) compared with that determined previously in Azotobacter chroococcum and in Clostridium pasteurianum. The high value was probably not due to unfavourable temperature, phosphate concentration or pH. The apparent ATP requirement for N, fixation was probably no lower in 0,-limited chemostat cultures than in anaerobic glucose-limited chemostat cultures. When hydrogen was introduced into the atmosphere over the anaerobic glucose-limited chemostat culture, there was an increase in the apparent ATP requirement for N, fixation and in the activity of nitrogenase in intact organisms. A comparison of these increases suggests that some ATP is wasted by the ATP-dependent H,-evolving activity of nitrogenase.

Pathways of Energy Metabolism Required for Phenotypic Expression of Nif+Kp Genes in Escherichia Coli

“…It was also found that the unc+ and uncB-hybrids grew anaerobically to the same extent as each other in NFM, although the growth yield was about 55 % less than in NFM with excess ammonium (Fig. 3) (Hill 1976). When log-phase cultures of AN283(FN68) growing…”

“…C Assuming 2·9 mol ATP used per mol glucose (Hadjipetrou et al 1964;Hill 1976). Assuming that the energy requirements for maintenance in the nitrogen-fixing and ammonia-assimilating cells are similar (HilI 1976), then the difference between the two values for ATP molecules available (i.e. 37) will be the number required for fixation of N2.…”

“…Studies of nitrogen-fixing bacteria have indicated that this consumption is somewhere between 4 and 30 moles of ATP per mole of N 2 fixed (Daesch and Mortenson 1968; Dalton and Postgate 1969;Postgate 1972;Hill 1976). This ATP can be synthesized either by substrate level phosphorylation or by electron-transport-dependent phosphorylation (Haddock 1977). ATP is synthesized anaerobically by the complex membrane-bound A TP pyrophosphatase (ATPase; EC 3,6.1.8) protein, which can be coupled to the electron flow to nitrate or fumarate as terminal electron acceptors ( Fig.…”

“…A further molecule of ATP can then be generated from pyruvate, giving about 3 ATP molecules per glucose molecule by substrate level phosphorylation (Hadjipetrou et a/. 1964;Hill 1976).…”

Biochemical Genetics of Nitrogen Fixation

“…For instance, an excess of component I leads to a higher ratio of ATP to electrons transferred (127). In vivo, a constant ratio of these two components is maintained by having the three structural genes (in K. pneumoniae, at least) being part of a single operon, nifHDK (134,142 (97) and 20 ATPs are required in C. pasteurianum (49). The relationship between NH4' formation and carbon substrate used was studied with a derepressed mutant of K. pneumoniae that was not able to assimilate the NH4' produced by N2 fixation (4).…”