Rhizobium japonicum bacteroids isolated from soybean (Glycine max L.) nodules oxidized "C-labeled succinate, pyruvate, and acetate in a manner consistent with operation of the tricarboxylic acid cycle and a partial glyoxylate cycle. Substrate carbon was incorporated into all major cellular components (cell wall + membrane, nucleic acids, and protein).Much research has been done on select aspects of nitrogen fixation by leguminous plants, such as nodule formation and the biochemistry and regulation of nitrogen fixation. However, relatively little attention has been given to carbon metabolism in nodules. Since nodular metabolism ofcarbon compounds provides both the reductant and energy source to support nitrogen fixation, as well as furnishing carbon skeletons from which amino acids are synthesized and transported from the nodules to aerial portions of the plant, we thought that an overview of nodule carbon metabolism represented a logical extension of existing knowledge of nodule function.There is good evidence that cultured Rhizobiumjaponicum cells possess a functional TCA' cycle (6,7). Although several researchers have assumed that bacteroids also possess a TCA cycle (1,2,12, 16) (4,11,14). Fresh wt of nodules was determined and the nodules were surface-sterilized for 5 min in 10 ml of 4% (w/v) NaCIO and rinsed several times in a total volume of 200 ml of sterile distilied H20. All subsequent steps were performed under aseptic conditions. Nodules were crushed in 10 ml of sterile 0.1 M Na-phosphate buffer (pH 7.4), and filtered through four layers of cheesecloth. The filtrate was centrifuged at l,OOOg for 5 min. The pellet of bacteroids was washed once with P04 buffer. Bacteroid preparations contained approximately 2 mg of protein/ml for field-grown plants and 0.8 mg of protein/ml for greenhouse-grown plants. Protein was determined by the Lowry method (10), modified by boiling the bacteroids in 0.1 M NaOH for 10 min to solubilize the protein prior to adding the reagents used in the Lowry assay.Radiorespirometry

Networked multimedia microcomputers provide new ways to help students learn chemistry and to help instructors manage the learning environment. This technology is used to replace some traditional laboratory work, collect on-line experimental data, enhance lectures and quiz sections with multimedia presentations, provide prelaboratory training for beginning nonchemistry- major organic laboratory, provide electronic homework for organic chemistry students, give graduate students access to real NMR data for analysis, and provide access to molecular modeling tools. The integration of all of these activities into an active learning environment is made possible by a client-server network of hundreds of computers. This requires not only instructional software but also classroom and course management software, computers, networking, and room management. Combining computer-based work with traditional course material is made possible with software management tools that allow the instructor to monitor the progress of each student and make available an on-line gradebook so students can see their grades and class standing. This client-server based system extends the capabilities of the earlier mainframe-based PLATO system, which was used for instructional computing. This paper outlines the components of a technology center used to support over 5,000 students per semester.