A changed nitrogenase activity inRhodospirillum rubrumafter substitution of tungsten for molybdenum

✍ Scribed by H. Paschinger

• Book ID: 104780263
• Publisher: Springer
• Year: 1974
• Tongue: English
• Weight: 613 KB
• Volume: 101
• Category: Article
• ISSN: 0302-8933
• DOI: 10.1007/bf00455954

✦ Synopsis

The nitrogenase activity in Rhodospirillum rubrum was changed when the cells were made either Mo-deficient or when Mo was replaced by tungsten (W) as trace element in the growth medium: In the absence of N~, normal Mo cells evolved ]-I 2 (via nitrogenase) from added malate in the light faster than W ceils, which in turn evolved H 2 faster than Mo-deficient cells. In the presence of N 2, on the other hand, nitrogen fixation rate in W cells was very close to the low rate found with Mo-deficient cells.

Incubation after harvesting of Mo-deficient cells with 2 X 10 -5 M molybdate or tungstate stimulated the H 2 evolution (similarly with both trace elements) as well as the N 2 fixation (Mo was more effective than W). This indicates that the nitrogenase activity of W cells was truly caused by W and not merely by remaining traces of Mo.

The ATP consumption is apparently higher with a W-containing nitrogenase than with the normal Mo-nitrogenase. :Further, the affinity to ~q2 of the W cells seems to be lower than with the Mo cells.