Diversity and Dynamics of Indigenous \u3cem\u3eRhizobium japonicum\u3c/em\u3e Populations

A simple method, based upon the separation of cellular proteins by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis, has been devised for distinguishing between isolates of Rhizobium japonicum. Eleven laboratory strains, previously classified into five serogroups, were analyzed by gel electrophoresis. Groups determined subjectively according to protein patterns matched the serogroups, with one exception. Most strains within serogroups could be distinguished from one another. For studying the ecology of Rhizobium, an important advantage of this technique compared with serology or phage typing is that it discriminates among previously unencountered indigenous bacterial isolates as well as among known laboratory strains. SDS-gels were used to analyze the Rhizobium population of 500 nodules, sampled throughout the growing season, from soybeans at two different Wisconsin localities. Although the soybeans had been inoculated with laboratory strains of R. japonicum, indigenous R. japonicum predominated. At one location, 19 indigenous gel types were distinguished and classified mainly into four groups. At the other location, 18 gel types, falling mainly into three groups, were detected. The predominance of a particular group varied, in some cases dramatically, depending upon the time and depth of nodule formation

Genetics of nitrogen fixation : (nitrogenase, molybdenum, ammonium excretion, legumes)

Recent advances in understanding the genetics of nitrogen fixation have provided ideas for novel application of nitrogenase and nitrogen-fixing organisms. Mutant strains have been useful for identifying the active site of nitrogenase and for identifying other factors, besides nitrogenase, that are specifically required for an organism to fix nitrogen. These strains have been important tools for assaying such factors during their purification. A fine-structure map of Klebsiella pneumoniae was obtained by deletion mapping of many nif (nitrogen fixation) mutations. Transformation between Nif[superscript minus sign] mutant strains of Azoto bactervinelandii has shown that the nif genes are scattered around the chromosome, unlike the situation in K. pneumoniae in which nif genes are clustered. Regulatory mutations have been useful for constructing derepressed ammonium-excreting strains in A. vinelandii. Such strains can fertilize the roots of cereal plants. The regulation of nitrogen fixation seems to be quite complex since ammonium, oxygen, and molybdenum all play a role in nitrogenase synthesis in K. pneumoniae. The Rhizobium-legume symbiosis has been studied with mutant strains of Rhizobium that are unable to form root nodules and mutant strains which form root nodules unable to fix nitrogen. Several strains that do not infect the host plant lack a surface polysaccharide that is present in wild-type cells. Some mutant strains of Rhizobium cause leghemoglobin deficient nodules to be formed. Another mutant phenotype causes the plant to fix more nitrogen than the wild type. Such strains might have potential use in agriculture.WINSTON J. BRILL, Dept. of Bacteriology and Center for Studies of Nitrogen Fixation, University of Wisconsin, Madison, Wisconsin

\u3cem\u3eRhizobium japonicum\u3c/em\u3e Mutants Defective in Symbiotic Nitrogen Fixation

Rhizobium japonicum strains 3I1b110 and 61A76 were mutagenized to obtain 25 independently derived mutants that produced soybean nodules defective in nitrogen fixation, as assayed by acetylene reduction. The proteins of both the bacterial and the plant portions of the nodules were analyzed by two-dimensional polyacrylamide gel electrophoresis. All of the mutants had lower-than-normal levels of the nitrogenase components, and all but four contained a prominent bacteroid protein not observed in wild-type bacteroids. Experiments with bacteria grown ex planta suggested that this protein was derepressed by the absence of ammonia. Nitrogenase component II of one mutant was altered in isoelectric point. The soluble plant fraction of the nodules of seven mutants had very low levels of heme, yet the nodules of five of these seven mutants contained the polypeptide of leghemoglobin. Thus, the synthesis of the globin may not be coupled to the content of available heme in soybean nodules. The nodules of the other two of these seven mutants lacked not only leghemoglobin but most of the other normal plant and bacteroid proteins. Ultrastructural examination of nodules formed by these two mutants indicated normal ramification of infection threads but suggested a problem in subsequent survival of the bacteria and their release from the infection threads

Scheduling with Sequencing Flexibility *

This study examines the effects of sequencing flexibility on the performance of rules used to schedule operations in manufacturing systems. The findings show that taking advantage of even low levels of sequencing flexibility in the set of operations required to do a job results in substantial improvement in the performance of scheduling rules with respect to mean flowtime. Differences in the mean flowtime measure for various rules also diminish significantly with increasing sequencing flexibility. Performance improvements additionally result for such due-date related performance measures as mean tardiness and the proportion of jobs tardy. At high levels of sequencing flexibility, some nonparametric scheduling rules outperform the shortest processing time rule in terms of the mean flowtime criterion. Rules based on job due dates also outperform rules based on operation milestones in terms of tardiness related criteria at high levels of sequencing flexibility. The implications of these findings for the design of manufacturing systems and product design are noted.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73893/1/j.1540-5915.1993.tb00477.x.pd

Use of microorganisms for crop agriculture

Microbial inoculants have the potential to increase crop yield without damaging the environment. Current regulations and guidelines strongly inhibit advancement, without protecting our health and environment, in spite of our extensive experience with genetically altered microorganisms. Agenciesl should design regulations appropriate for research and commercialization and create a balance between protecting the public from problems while helping it to benefit from desirable agricultural practices

Biotechnology and Plant Agriculture

(Abstract taken from the 1990-91 DSLS Program). Formerly Vilas Research Professor of Bacteriology at the University of Wisconsin, Madison, and founder and Vice President of Research and Development of the Agracetus Corporation of Middleton, Wisconsin, Dr. Brill has recently formed a new company. Winston J. Brill & Associates, to assist corporations in improving research productivity and creativity. Dr. Brill was born in London, received his B.A. from Rutgers University in 1981, and earned his Ph.D. in microbiology at the University of Illinois, Urbana, in 1965. After obtaining his doctorate, he was involved in research at the Massachusetts Institute of Technology from 1965 to 1967 as a National Institute of Health Postdoctoral Fellow. Dr. Brill was then appointed assistant professor of bacteriology at the University of Wisconsin, Madison, where he served as associate professor full professor and Vilas Research Professor. He is currently an adjunct professor in the Department of Bacteriology. In 1981 Dr. Brill founded the Agracetus Corporation, and served as its vice president and director of research until 1989. He has also served on the National Institute of Health Recombinant DNA Advisory Committee I1973—1983), the Genetic Engineering Advisory Panel to the U.S. Secretary of State (19811, and the U.S. Department of Agriculture P0licy Advising Committee (1985—present). Dr. Brill has received numerous honors, including the Eli Lilly Award in Microbiology and Immunology and the Alexander von Humboldt Foundation Award, both in 1979. He was elected t0 the National Academy of Sciences His work: Dr. Brill is a leader in the area of agricultural applications of biotechnology with approximately 160 publications, one patent, and two patents pending in the field. He has served on numerous committees aimed at evaluating the safety and effectiveness of genetic engineering in plants. His own research focuses on the use of genetic engineering to understand and to manipulate the process of nitrogen fixation in plants.https://digitalcommons.bard.edu/dsls_1990_1991/1002/thumbnail.jp