w. KlingmUller Lehrstuhl fUr Genetik, Universitat Bayreuth, UniversitatsstraBe 30, 8580 Bayreuth, FRG th th On September 6 and 7 1983 the second workshop on "Azospirillum: Genetics, Physiology, Ecology" took place at the University of Bayreuth, west Germany, organized by the genetics department. There were about 50 participants, who came from German research institutions, from other European countries, from Israel, Egypt and North and South America. The first such workshop had taken place two years ago in Bayreuth too, hence the organizers could draw on the experiences then obtained. Azospirilla have, during the past ten years, found an ever increasing scientific interest, because first, these soil bacte ria carry the genetic information for binding molecular nitrogen from the air, and second, they live in close vicinity to the roots of several grain crops and forage grasses. By exploitation of these two properties, it is hoped to develop inoculation pro cedures that result in yield increases in agriculture, in par ticular in soils poor in nitrogen. The reports on the first afternoon focussed, as a result of the Bayreuth research interest, on the genetic basis and the regulation of nitrogen fixation in Azospirillum. Here, mainly by application of most modern gene technological approaches, considerable progress in the understanding of the situation has been made, and was documented in the corresponding reports.

Inhalt
Ten Years Azospirillum.- Genetic Analysis in Azospirillum.- Recent Developments in the Genetics of Nitrogen Fixation in Azospirillum.- Molecular Cloning of Nitrogen Fixation Genes from Azospirillum.- Site-Directed Transposon Mutagenesis of Cloned nif-Genes of Azospirillum brasilense.- Uptake and Fate of Plasmid-DNA in Azospirillum lipoferum A23.- Nif Mutants of Azospirillum brasilense: Evidence for a Nif a Type Regulation.- Mutants of Azospirillum Affected in Nitrogen Fixation and Auxin Production.- Motility Changes in Azospirillum lipoferum.- Attraction of Azospirillum lipoferum by Media from Wheat-Azospirillum Association.- Nitrogen Fixation and Denitrification by a Wheat-Azospirillum Association.- Effect of Oxygen Concentration on Electron Transport Components and Microaerobic Properties of Azospirillum brasilense.- Nitrogen Fixation (C2H2 -Reduction) and Growth of Pure and Mixed Cultures of Azospirillum lipoferum, Klebsiella and Enterobacter sp. From Cereal Roots in Liquid and Semisolid Media at Different Temperatures and Oxygen Concentrations.- Ecological Factors Affecting Survival and Activity of Azospirillum in the Rhizosphere.- Forage Grasses Inoculation with Gentamicine and Sulfaguanidine Resistant Mutants of Azospirillum brasilense.- Association between Wheat and Azospirillum lipoferum under Grenhouse Conditions: Increase of Yield and Thousand Corn Weight.- Benefits of Azospirillum Inoculation on Wheat: Effects on Root Development, Mineral Uptake, Nitrogen Fixation and Crop Yield.- Contribution of Azospirillum SPP. to Asymbiotic N2 -Fixation in Soils and on Roots of Plants Grown in Egypt.- Resumé.- List of Participants.