The Biochemistry of the Nitrifying Organisms
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چکیده
Growth of the organisms. Nitrobacter was obtained from an Aberdeen garden soil by serial subculture in a medium made up as follows. To 10 1. ofwater were added 30 g. ofKH2P04, 1 g. of CaSO4, 0 5 g. of MgCl2, 0 01 g. of MnCl2, 0-2 ml. of dialysed iron (B.P.). By addition of lOM-NaOH, the pH was adjusted to 7-8, which is the optimum pH for the strain of Nitrobacter used (Lees, 1954). The solution was filtered and, after addition of the appropriate amount of NaN02, sterilized at 1200 for 20 min. This medium (medium G) was used also for the propagation of the stock cultures which provided inocula for large-scale batch cultures. For largescale batch cultures 100 ml. of the carbonate-phosphate suspension, used by Lees (1952) for the culture of Nitrosomonas, was added to each 101. of medium G before sterilization. Batch cultures were used for preparing suspensions of Nitrobacter cells suitable for biochemical study; the carbonate-phosphate suspension was added to facilitate the separation of these cells after growth. Nitrobacter, unulike Nitrosomonas, does not require a solid surface for growth, but Nitrobacter cells did adhere in some measure to the solid particles in the suspension and, in any case, were entrained by them when the cells were separated from the bulk of the medium by centrifuging. The cells were grown at 280. Stock cultures were carried in conical flasks; the depth of the medium was always less than 1 cm., to ensure adequate aeration. Batch cultures were grown in 101. of medium in 101. bottles, each fitted with a glass sparger through which air was pumped at about 10 1./min. The air was sterilized by passing it through 0 1 M-CuS04 in N-H2S04, then through a sterilized cottonwool plug. A fresh stock, or batch, culture was initiated by inoculating the sterilized culture medium (containing 70 ,ug. of N/ml., as NaNO2) with about 1% of its volume of stock culture. Samples of the newly inoculated culture were
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The Biochemistry of the Nitrifying Organisms 4. THE RESPIRATION AND INTERMEDIARY METABOLISM OF NITROSOMONAS BY T. HOFMAN
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