Robert H. Burris
Wolf Prize Laureate in Agriculture 1985
Robert H. Burris
Affiliation at the time of the award:
College of Agriculture and Life Sciences, University Of Wisconsin, USA
“for his pioneering fundamental research on the mechanisms of biological nitrogen fixation and its application in crop production.”
In the air above every hectare of land there are about 78 tons of elemental nitrogen. The latter is chemically inert and, under ordinary conditions, does not react with other elements. Hence most crop plants are likely to be starving in this sea of nitrogen. Only when the nitrogen in the air is combined with other elements it is possible for plants to use this nitrogen in their growth processes.
The mere fact that some bacteria are able to use the elemental form of nitrogen that exists in the atmosphere has been known for nearly 100 years since its discovery by the Russian biochemist S. N. Vinogradsky. Thus, these nitrogen-fixing bacteria can grow in the absence of combined nitrogen and, at the same time, produce nitrogenous substances in the soil that may be used later by crop plants.
However, during the first fifty years since the discovery of biological nitrogen fixation by soil-inhabiting bacteria, very little information was available as regards the biochemical mechanisms involved. This was quite surprising in view of the paramount importance of this process in the nitrogen budget of our globe.
The state of the knowledge regarding this wonder of nature has changed dramatically in the late 1930’s and early 1940’s when Professor Burris investigations on the basic chemistry and physiology of the microorganisms that fix nitrogen, actually opened up an entire new vista of basic research on biological nitrogen fixation. He was the first to use a radioactive isotope of nitrogen (15N) in this study, which led to the discovery of ammonia to be the key intermediate in this biochemical process.
For over 45 years, following these pioneering efforts, Professor Burris and his colleagues have purified and studied in great detail and depth the complex of enzymes involved, and the metabolic pathways followed in this natural phenomenon. At the same time they developed novel techniques for reliable, quantitative assay of the nitrogen fixing activity of microorganisms.
The scope of his research in this particular area has not been limited to the well recognized nitrogen-fixing bacteria that live in symbiosis with leguminous, plants in nodules formed on their roots. His studies also embraced the free-living microorganisms that are able to fix atmospheric nitrogen. Mention should be made in this connection of Prof. Burris pioneering work on Azospirillum – a free-living nitrogen-fixing genus of bacteria associated with plant roots, in particular cereal plants.
One may sum up Burris’ contributions to fundamental biochemical research on nitrogen fixation by concluding that his very careful, thorough investigations have been in the heart of the efforts to elucidate the mechanism of this life-supporting process. He has thus rightly earned the title of ‘world doyen of nitrogen fixation.
Because of the pressing food needs of the world on one hand, and the rising cost of chemical nitrogen fixation for use in mineral fertilizers on the other, the subject of biological nitrogen fixation is currently receiving greatly increased attention throughout the world.
The lifelong fundamental studies of Prof. Burris provided the scientific background for the now worldwide practice of inoculating legume crops with industrially manufactured pre-cultured strains of nitrogen-fixing bacteria. The latter are capable of supplying essentially all the nitrogen requirements of the plan~ Furthermore, the highly sensitive techniques developed by Prof. Burris for measuring this biological activity, proved most instrumental in the selection of more effective strains of bacteria for this purpose.