By Academician Igor TIKHONOVICH (Russian Academy of Agricultural Sciences), All-Russia Institute of Agricultural Microbiology
According to contemporaries of the day, already late in the 19th century agronomy was forging ever closer ties with biology. Soil was no longer regarded as dead matter but rather as a living organism populated by myriads of microscopic wights responsible for so many chemical processes there.
The beginnings of our agricultural microbiology go back to the year 1891 when the St. Petersburg-based Department of Land Use set up an agricultural bacteriological laboratory for making use of microorganisms in combating rodents. Catering to the urgent needs of land farming, that laboratory was to shoulder a variety of jobs in upgrading the techniques of bacteriological struggle against pests by infecting them with deadly diseases. Such were the laboratory's priorities.
Among the pioneers and trailblazers of our science were the outstanding microbiologists K. Merezhkovsky and B. Isachenko (elected to the national Academy of Sciences in 1946). And even though their laboratory was still concerned with "mice-killing" microorganisms by and large, it also undertook research into the microbiology of wine- and cheese-making, and in other areas too. These studies played a major role in assimilating the latest achievements by the nation's farm industry.
Our All-Union (now, All-Russia) Institute of Agricultural Microbiology was founded in 1930 by a research team headed by Academician S. Kostychev, a biologist, physiologist and biochemist, all in one. And so he had a good understanding of the natural schemes of things. That is why our research scientists continue to be closely involved with a large group of
microorganisms vital to soil formation and responsible for the formation of agrophytocenoses, for the biological control of a range of major plant diseases and pests. An important part of our work is to keep exploring for new varieties of bacteria and fungi so as to identify their useful functions and develop adequate application techniques.
Our institution today is the chief component of Russia's national school of agricultural microbiology. Eminent scientists have been on our research staff, such as Academicians Ye. Mishustin, G. Nadson, I. Samoilov (members of the national Academy of Sciences), G. Muromtsev and O. Berestetsky (members of the national Agricultural Academy); also, V. Israilsky, G. Seliber, among others. Our alumni are working in many foremost laboratories of Russia and other countries (Great Britain, France, Germany, the Netherlands, Australia and elsewhere).
Since the very beginning our institute has been giving priority to basic problems of microbiology and to the practical application of innovative techniques in farm production. Our equipment is good enough: we have a gene sequencer, chromatographs and a computer net; all that enables us to keep up-to-date in our research.
International cooperative projects offer us essentially new opportunities.
Such projects involve joint effort of many laboratories and countries (we are cooperating with our colleagues in Europe, the United States, Australia, Japan and South Korea). Since biological models developed by us often underlie joint ventures like that, this cannot but boost the prestige of our institute. It is not accidental that we stood behind the Tenth Congress on Biological Fixation of Nitrogen, one that was attended by more than 700 scientists from 72 countries. At the moment we are getting ready for another international congress-on molecular interaction of microorganisms and plants, due in St. Petersburg later in the year.
One important problem that agricultural microbiology is addressing is to elucidate the role of microorganisms in the agricultural landscape. We must pinpoint significant microbial species and study their functions. If we find them good, we should select such species and introduce them into the ambient medium with the aim of regulating, in the long run, soil-and-microbiological processes. We have made some progress in the use of rhizosphere* microorganisms, including nodule (legume) bacteria which, in symbiosis with legumes, assimilate atmospheric nitrogen and enrich the topsoil with it; and we have made headway in employing useful as well other microorganisms. We have gathered a comprehensive collection of rhizobacteria found in this country and abroad, in different parts of the world, and with their aid are improving crop inoculation techniques. Every year we check up on the efficiency of bacterial strains already in use and those holding promise-we do that in what we call a geographical grid of experiments.
Even at the present stage the study of nodule bacteria-by using gene engineering methods-allows to design corresponding strains combining a variety of useful characters-namely, high-performance symbiosis and enhanced competitiveness; besides, we are to begin work on a genomic typing of the active pairs "bacterial strain/ host plant".
Apart from legume microorganisms, we have identified yet another rhizospheric group and have tested it. In this pioneering effort our institute has created a new generation of biopreparations. First, we selected useful microorganisms according to a nitrogen-fixation capability-we took them from the roots of nonlegumes. And then we found out that using them we can boost crop productivity through combined effects.
The problem of microbe/plant interaction has moved to the forefront due to the progress of ecologically sus-
* Rhizosphere-topsoil next to plant roots.- Ed.
tained land farming based by and large on optimization of the natural potential of agrophytocenoses. Evolution-ally, plants and microorganisms obey the principle of segregated functions, with the plants kind of delegating some of their characters to the cohabitants, that is, the microorganisms. If this relationship is destroyed in the course of present-day economic management, landfarmers have to make for the deficient functions and, in so doing, they upset the ecological equilibrium. The phytopathogenic relations thus formed in the rhizosphere become part of one genetic system catering to the interests of the pathogenic microflora.
We can minimize the phytogenesis-caused damage either through targeted regulation of the host plant/bacterium relationship or by means of useful microflora suitable for combating soil infections. A knowledge of the processes underlying the susceptibility of crops to various diseases or, conversely, their resistance will enable us to adopt new approaches in breeding resistant (immune) crop strains. Our institute is cooperating in this area with St. Petersburg State University. Proceeding from available data, we aim to look into the effect of symbiotic bacteria on the induction of the systemic acquired resistance (SAR) of plants to pathogens. In this way we shall be able to obtain strains of endosymbiotic and associative bacteria good for the immunization of farm crops. Yet another prospect is that of developing practical ways of using bacterial strains both in hothouses and on open ground. Here our method of active selection will be used, and it will give rise to organisms combining a high colonizing ability with a growth-stimulating and anti-pathogenic activity.
From our school days we remember: that legumes form two types of sym-bioses-with nodule bacteria and with endomycorrhizal fungi implicated in the mineral nutrition of host plants. The high efficiency of these two systems is ensured by specialized structures (and organs as well) which are of great interest to us for understanding the mechanisms of interaction between the symbiotic partners: exchange of molecular signals, coordination of differential gene expression, differentiation and de- differentiation of cells and tissues, genesis of the partners' structures and organs, and evolution of the symbiotic formative process. Here we are giving particular attention to developing model systems that will make us better understand the molecular mechanisms of interaction between symbionts and help us to pinpoint the stock material for pea-breeding so as to enhance the potential of this culture for coexistence with bacteria. For this purpose we are studying genetic control over legume-rhizobial and endomycorrhizal symbioses by the host plant-that is we are identifying respective genes, studying their primary structure and functions of molecular products.
We at our institute have gathered one of the world's largest collections of the pea mutants identified to this day (120) according to the above characters. Their phenotypic characteristics has made it possible to determine discrete stages in the growth of both nitrogen-fixing tubercles and of the arbuscular mycorrhiza* controlled by different groups of pea genes. We have found some of these genes to be vital to the growth of both endosymbiotic systems.
The detailed phenotypic description and genetic mapping of the identified symbiotic genes of pea create good conditions for their cloning for the purpose of further analysis of their primary sequence, the structure of their molecular products and gene expression regulation.
Since, as said above, both endosymbiotic systems possess common plant genes and molecular products, this means that legumes have a genetic system controlling the growth of related nodule bacteria and arbuscular mycorrhiza fungi. Such a conclusion showed the necessity of pea selection depending on the impact on the effectiveness of this "triple community". As it turned out, it is quite possible to breed
* With reference to arbuscles-here, specialized organs of mycorrhizal fungi growing in plant roots.- Auth.
commercial varieties of pea with a high symbiotic potential.
Soil monitoring and the ecology of soil microorganisms have always been an important part of our work. We have shown that certain herbicides, getting into the roots of legumes, are accumulated in their tubercles to be decomposed by bacteria. So an analogous procedure can be employed for a biological cleansing of pesticide contaminated soils. We have isolated adequate microorganisms and devised methods of speeding up soil self-purification processes whereby poisons are eliminated.
The study of microbial complex formation processes in soil triggered by natural and anthropogenic factors has caused us to turn to microbiological methods of soil quality assessment and to a system of microbiological monitoring of topsoil in agroecosystems.
To enrich soil with organic matter, we have developed a new generation of fertilizers from wastes of large stock-breeding complexes. Such fertilizers offer a happy combination of chemical fertilizer standards with the ecological safety of manure or peat. We have also advanced an ecophysiological principle of assessing the performance of microbial communities in artificial ecosystems. So now we can determine and exclude factors inhibiting the microbiological oxidation of organic wastes. Thus we could obtain new kinds of microbial fertilizer having a high concentration of essential biogenic elements and of useful micro-flora, and showing a good growth-stimulating activity and antagonistic effects on phytopathogenic fungi.
Microbiological procedures of combating agricultural pests have been known for well over a hundred years now. Still, our institute and other research centers throughout the world have not phased down research in pathogens targeted against insects and rodents. A large series of entomophilic and entomopathogenic microorganisms (i.e. those acting on insects) has been identified. We have studied their characteristics and selected some of them for the production of new ecologically friendly preparations, such as bactorodencide (against murine rodents), bitoxybacillin (against the Colorado potato beetle and pestiferous squamous-and-alate insects), bactoculicide (against gnats), bacicol (against hard-winged beetles), actinin (against spider ticks), among other drugs. Today we are working on preparations that could be used in minor doses- in hundredth fractions of the conventional remedies-against pests and destructive insects. We are also developing combination preparations for combating destructive insects and phytopathogenes simultaneously.
The silo leaven, a preparation well known here in Russia, was first obtained at our institute by a research team under L. Carder. It is a real alternative to costly chemical preservatives imported from other countries. This ferment boosts milk yields and is widely used in the feed industry.
At the initiative of Academician L. Ernst, member of the Russian Academy of Agricultural Sciences, we have begun studies into the microbiology of digestion in the rumen of cud-chewing animals (ruminants) and developed a new preparation, cellobacterin, which is performing quite well in cattle- and hog-farming, in poultry- keeping and in intensive fish-breeding. Its application allows to cut down expenses for fowl feed and reduce the concentration of costly soya schrot imported from abroad and added to the feed; we can even replace the soya schrot with the low-cost sunflower schrot and bran, both produced at home, and not at the cost of productivity.
Looking back, we can only take pride in the work accomplished by this country's microbiology in these hundred and some years, and we are looking into the future with optimism-for we are just at the beginning of the path of ever new discoveries and accomplishments.
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