MOLYBDENUM AS A MICRONUTRIENT FOR NITROBACTER.

Finstein, M. S. (University of California, Davis), and C. C. Delwiche. Molybdenum as a micronutrient for Nitrobacter. J. Bacteriol. 89:123-128. 1965.-The requirement of Nitrobacter for molybdenum was investigated by use of a medium purified by chemical means, as well as by depletion by the prior growth of this autotrophic bacterium. During 5 days of growth, added molybdenum induced an approximately 11-fold increase in both nitrite utilization and cell-mass development. In short-term studies, maximal response was obtained with concentrations as low as 10(-9)m. No other metal tested substituted for molybdenum. It is estimated that a minimum of 2,000 atoms of molybdenum is required for the synthesis of one Nitrobacter cell. Molybdenum did not directly influence the thermodynamic efficiency of Nitrobacter. The efficiency of molybdenum-deficient cultures and of cultures supplied with the micronutrient declined equally during the early stage of development, despite large differences in the amount of nitrite consumed. After the utilization of about 100 mumoles of nitrite per ml, cultures supplied with molybdenum became relatively less efficient. A procedure is described whereby large masses of Nitrobacter cells can be obtained with relative ease.