An increase in the availability of NO3 may result in a larger contribution from NO3 assimilation, however nodulation and nitrogenase activity may be decreased (4, 5, 16). The primary cause of this inhibitory effect by NO-is not clear and information is still lacking with regard to ways to relieve the inhibition of N2-ase activity by NO3-.Nitrite accumulation within the nodules has been shown in NO3--treated plants of several legumes including soybeans (15, 22). NO2-is a known inhibitor of several aspects of N2 fixation (12,19,21,24). However, Gibson and Pagan (6) and Manhart and Wong (15) have concluded that NO2 the product of bacteroid NR3, may not play a role in the inhibition of acetylene reduction by NO3-. These authors based their conclusions on whole plant studies. The use of whole plants may be helpful to obtain an integrated view of the relationships between NO3-reduction and N2 fixation but may be complicated by limitations imposed by the processes of NO% uptake, mobilization, storage, and reduction in compartments other than the nodules. Studies using isolated parts of the symbiotic system may provide more direct information on the metabolism of NO3 within the nodules and its relationship to N2 fixation. The availability ofNR-negative mutants ofRhizobium japonicum (25) facilitates such studies. Mutants lacking nitrate reductase (NR-), produced from R japonicum strain 61A76, have been shown to produce normal nodules and fix N2 in symbiosis with soybean plants (25). The objectives of this study were: (a) to characterize the relationships between NO-reduction, NO-reduction, and Nrase activity using detached soybean nodules and R japonicum bacteroids; (b) to reevaluate the role of the bacteroid NR as a mediator of the NO-effect on N2-ase activity and; (c) to develop NR-negative mutants of Rjaponicum tolerant to normally inhibitory levels of NOR.MATERIALS AND METHODS Plant and Bacteria Culture. The Rhizobium japonicum strain (USDA 110) used in this study was obtained from Dr. D. F. Weber (USDA at Beltsville, MD). The bacteria were cultured and mutant strains lacking NRA (NR-) were prepared and tested as previously described (25). In one experiment (Fig. 2), another R japonicum strain, 61A76, (obtained from Dr. J. C. Burton of the Nitragin Company, Milwaukee, WI) was used. Soybean (Glycine max L. cv Williams) seeds were provided by Dr. J. Justin (Soils and Crops Department, Rutgers University, NJ). Soybean seeds were surface sterilized by treatment with 700%o ethanol (v/v) for 5 min followed by extensive rinsing with distilled H20 prior to inoculation (107-I09 cells/ml). The surface-sterilized seeds were planted in an autoclaved mixture (1:1) of perlite and vermiculite in pots (20.5 cm diameter x 21.5 cm high). Each

The MDA/ALS Clinic at the University of California, San Francisco (UCSF) have recently transitioned our in-person multidisciplinary clinics to a successful, virtual patient experience. Here, we outline our new clinic model, presenting detailed information about our clinics’ virtual workflow and our experiences with this transition. In this way, we hope to demonstrate the feasibility of a large-scale virtual multidisciplinary clinic and assist other clinics (both local and academic) as they transition their care of patients virtually within the COVID-19 environment.

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