Strains Of Nodule Bacteria Research Articles

Evolution of legume-rhizobium symbiosis for an improved ecological efficiency and genotypic specificity of partner interactions

Mathematical simulation of the evolution of polymorphic legume-rhizobium symbiosis showed that co-evolution of the partners for an improved ecological efficiency of symbiosis is greatly stimulated when low-active N2-fixing and non-N2-fixing strains of nodule bacteria are prohibited from colonizing nodules. The results of analysis of the model were collated with the comparative morphology of the infection process in various legumes, and its was assumed that mechanisms controlling bacterial reproduction in nodules arose in early evolution of symbiosis in primitive legumes owing to a transition from mixed to clonal infection. The development of such mechanisms was associated with adaptively valuable macroevolutionary transformations of symbiosis and directed its microevolution towards a parallel increase in the specificity and efficiency of mutualism. The increase was due to a reorganization of selective processes in endosymbiotic bacterial populations, which was based on changes in their genetic and spatial structures and optimized metabolic feedbacks between the partners (preferential allocation of photosynthesis products to the most active N2-fixing strains).

Nodulation in Onobrychis Perennial Legume Plants

A total of 110 strains of nodule bacteria was isolated from plants Onobrychis transcaucasica and Onobrychis chorassanica. Nodulation study of bacteria in both Onobrychis plant species in microvegetation experiment gave a very low nodulation on plant roots. The intensive nodulation of Onobrychis plants was recorded in vegetation experiment and for Onobrychis transcaucasica the efficiently-nodulating strains were found OT102, OT103, OT117, OT121, OT130, OT136, ОT139, ОT140, while for Onobrychis chorassanica plants—ОC106, ОC107, ОC109, ОC112, ОT103, ОT117 and ОT123 strains. Nucleotide sequencing of the 16S rRNA gene and BLAST analysis showed that nodule bacteria of Onobrychis plants were related to Rhizobium, Burkholderia, Enterobacter and Pantoea genera. It has been shown a possibility of growing up of Onobrychis plants at minimal additional moisture of sabulous soils in the Kyzyl Kum Desert, creating artificial pastures and thereby immobilizing the desert blown sands.

The genetic control of specificity of interactions between legume plants and nodule bacteria

The genetic control of signal interactions between partners during formation legume-rhizobial symbiosis is examined. The ability of legumes to perceive the signal molecules (Nod-factors) excreting by nodule bacteria appears to be the base of these interactions. The diversity of receptor kinases in legume plants reflects the specificity of interactions with diverse strains of nodule bacteria.

THE INFLUENCE OF RHIZOBIUM GALEGAE STRAINS ON THE DEVELOPMENT OF PLANTS OF GALEGA OFFICINALIS AT FIRST AND SECOND YEAR OF CULTIVATION

The efficiency of inoculation of Galega officinalis by new strains of rhizobium allocated from nodules of the plant-owner was studied in conditions of field experience. Positive influence of bacterization of the plants by researching strains of nodule bacteria on the basic parameters of legume- rhizobial symbiosis as in the first and second year of vegetation of Galega officinalis is noted. Two strains R. galegae - Л-13 and Л-16 which promote increase in number nodules on roots of plants, activity symbiotic nitrogen fixation, contents of a chlorophyll in leaves of plants and productivity of Galega were selected by results of researches.

Productivity of soybean-rhizobium symbiosis after modification of root nodule bacteria activity with exogenous proteins

Plant growth experiments were conducted to assess symbiotic efficiency, photosynthetic rates, and the development of soybean (Glycine max (L.) Merrill) seedlings after seed inoculation with active and inactive strains of root nodule bacteria Bradyrhizobium japonicum preincubated in the presence homologous and heterologous proteins. The properties of active and inactive symbiotic strains were differentially modulated by homologous soybean lectin, which had a marked influence on plant physiological condition. The incubation of active rhizobia with a homologous lectin, i.e., lectin of the respective plant, increased the nitrogen-fixing activity of nodules and, consequently, elevated photosynthetic rates and weight increments in soybean plants. At the same time, the homologous lectin suppressed the symbiotic properties of inactive strain of nodule bacteria. The preincubation of rhizobia with a heterologous pea lectin had virtually no effect on functioning of symbiotic apparatus and photosynthetic rate, whereas the preincubation of root nodule bacteria with human albumin exerted an effect similar to that induced by a homologous lectin on symbiotic productivity.

Symbiotic efficiency of fodder galega (Galega orientalisLam.) andRhizobium galegaein ecological cultivation

One of the new strategies is rational production and use of leguminous plants. Recently, precisely for stated reasons, less known plant species that have ability of symbiotic relationship with rhizobium bacteria have been included in numerous and extensive research around the world (Italy, France, Germany, Norway, USA, Japan, Latvia). One of them is Galega orientalis Lam., new perennial (7-10 years) fodder leguminous plant that lives in effective symbiosis with Rhizobium galegae, recently described strain of nodule bacteria.

Effect of lucerne seed bacterization (Medicago sativaL.) on yield components in ecological cultivation

Biennial field experiments of parameter comparison for noninoculated and inoculated lucerne in ecological cultivation lead to conclusion that green mass yield was very significantly higher in inoculated lucerne, and dry matter yield was statistically very significantly higher in both research years. Nitrogen concentration in above ground part of plant material in both research years was significantly higher in inoculated lucerne. Protein yield of inoculated lucerne was two times higher (very significant) than of lucerne that was not inoculated with highly effective strain of nodule bacteria. From all above mentioned, we concluded that pre-sowing inoculation of lucerne seed with effective strain Sinorhizobium meliloti is necessary for obtaining higher, more sustainable yields. Besides, nitrogen fixed through root nodules of leguminous plants is cheaper, more natural and efficient for utilization by host plant. Rational use of soils and the maintenance of their multifunctionality is a key issue in sustainable systems.

ENHANCING THE GROWTH OF VICIA FABA PLANTS BY MICROBIAL INOCULATION TO IMPROVE THEIR PHYTOREMEDIATION POTENTIAL FOR OILY DESERT AREAS

Two experiments were conducted to investigate the effect of inoculating Vicia faba plants (broad beens) raised in clean and oily sand with nodule-forming rhizobia and plant-growth-promoting rhizobacteria (PGPR) on growth of these plants in sand and to test whether this can improve the phytoremediation potential of this crop for oily desert areas. It was found that crude oil in sand at concentrations < 1.0% (w/w) enhanced the plant heights, their fresh and dry weights, the total nodule weights per plant, and the nitrogen contents of shoots and fruits. Similar enhancing effects were recorded when roots of the young plants were inoculated with nodule bacteria alone, PGPR alone, or a mixture of one strain of nodule bacteria and one of the PGPR. Such plant growth effects were associated with a better phytoremediation potential of V. faba plants for oily sand. The total numbers of oil-utilizing bacteria increased in the rhizosphere and more hydrocarbons were eliminated in sand close to the roots. The nodule bacteria tested were two strains of Rhizobium leguminosarum and the PGPR were Pseudomonas aeruginosa and Serratia liquefaciens. The four strains were found to use crude oil, n-octadecane, and phenanthrene as sole sources of carbon and energy. It was concluded that coinoculation of V. faba plant roots in oily sand with nodule bacteria and PGPR enhances the phytoremediation potential of this plant for oily desert sand through improving plant growth and nitrogen fixation.

The application of immunofluorescence techniques to host plant/nodule bacteria selectivity experiments using Trifolium repens

Aseptically grown seedlings of Trifolium repens were inoculated with either pure cultures of two serologically distinct strains of Rhizobium trifolii or with a 50: 50 mixture. Identification of the strains of nodule bacteria was possible 66 h following inoculation and thereafter, at any time up to the harvest at 10 weeks. The identifications were carried out first on isolates from root hairs and later from direct microscopic observations of mature nodule sections. The antiserum for each strain was conjugated with fluorescein isothiocyanate which gave the specific bacterial smear or nodule centre a distinct bright green colour which was easily distinguishable from the deep blue of the non-specific strain. The experiment indicates how useful the immunofluorescence technique can be for rapid identification of nodule bacteria either in the very early infection stages or from mature nodules. The results clearly demonstrate that individual plants exerted selection for specific bacterial strains but not always for the same strains. The technique is discussed in terms of its use for ecological, bacterial strain competition and host selectivity experiments.

Influence of mineral fertilizers and inoculation on the formation of individual and seed productivity of soybean in conditions of the Right-Bank Forest-Step

Purpose. To establish the effect of seed inoculation with a microbial preparation of multifunctional action based on nitrogen-fixing and phosphorus-mobilizing bacteria and different doses and terms of mineral fertilizing on formation of individual and seed productivity of soybeans in the Right-Bank Forest-Steppe. Methods. Field (to study the interaction of the object of study with biotic and abiotic factors), test sheaf (to determine the individual productivity of plants), harvesting (to determine the seed yield), statistical (to determine the probability of research results), comparative calculation. Results. According to the research results, the most favourable conditions for the optimal parameters of plants individual productivity formation of early-maturing soybean of the Vilshanka and medium-ripening Suzirya varieties were created due to the seeds inoculation by phosphonitragin and mineral fertilizing in the dose of N30P60K60 + N15 in the phase of budding, what positively affected the level of yield as a whole. Conclusions. The technology model for intensive growing of the Vilshanka and Suzirya soybean varieties, which involves the use of seeds inoculation by a bacterial preparation based on strains of nodule bacteria (Br. Japonicum) and phosphate-mobilizing microorganisms (B. mucilaginosus) and introduction of N30P60K60 in the main fertilizing and extra-feeding with N15 provided the highest values of individual and seed productivity: the number of beans (24.7 and 28.8 pcs/plant, respectively), the number of seeds (51.0 and 56.1 pcs/plant), the weight of 1000 seeds (147.2 and 144.6 g), yield (2.91 and 3.17 t/ha). The organized factors ensured the optimal height of the lower bean attachment on the plant, which had a positive effect on yield preservation and facilitated mechanized harvesting. Improving the technology of growing the Vilshanka and Suzirya soybean varieties on the basis of bacterial and mineral nutrition has led to the highest level of profitability, respectively 124 and 160%, and energy efficiency ratios (2.20 and 2.40).

Overwintering of Clover Nodules in Alpine Conditions

As part of a programme investigating soil conservation in the Snowy Mountains area of New South Wales, trials were conducted in which seedlings of Trifolium ambiguum M. Bieb. and T. repens L. (Ladino clover) were planted in the spring of 1960 in eroded areas on Carruthers Peak adjacent to Mt. Kosciusko (lat. 36� 24'S., long. 14So IS'E.) at an elevation of about 7000 ft. Seedlings were raised in seed boxes of soil which had been massively inoculated with appropriate strains of nodule bacteria. Effectively nodulated seedlings were transplanted into peat cups filled with soil. This step was necessary because of the extreme host variation with respect to nodule formation and effectiveness in T. ambiguum (Hely 1957, 1963). The cups were planted intact together with a complete fertilizer mixture; at that stage all plants were well nodulated and the soil in the cups contained large numbers of nodule bacteria.

Variation in symbiotic effectiveness in subterranean clover (Trifolium subterraneum L.)

(1) The symbiotic effectiveness of 15 varieties and of four tetraploid lines of subterranean clover were examined in association with several strains of nodule bacteria.(2) Relatively- small but significant differences in yield occurred between host' varieties, and the varietal order of response depended somewhat on the bacterial strain, but not enough to shorn- any well-defined variety-strain specificity. (3) Hybridization between varieties increased yields slightly in F2, less in F3, and the effect disappeared in F4. (4) With one doubtful exception all attempts to alter effectiveness by selection or breeding within hybrid material failed.

Effect of specific polysaccharides from the host bacteria and of ribonuclease on the multiplication of rhizobium phages.

Two serologically unrelated strains of nodule bacteria produced two different polysaccharides, only one of which precipitated with antiserum to its parent bacterium. Both polysaccharides interfered with the multiplication of two bacteriophages in liquid cultures of the two bacterial strains, each of which was susceptible to only one of the two bacteriophages. One polysaccharide was slightly more effective than the other in interfering with multiplication of both bacteriophages: one phage was much more susceptible than the other to the interfering action of both polysaccharides. Crystallized pancreatic ribonuclease interfered with multiplication of bacteriophages much more strongly than did the polysaccharides. Neither the polysaccharides nor ribonuclease destroyed the phage particles.

The field distribution of strains of nodule bacteria from species of Medicago

Tests of nodulation and ability to fix nitrogen, together with serological reactions, are reported for localized isolates from Medicago hispida var. denticulata and M. laciniata. For a particular host species strains were distributed randomly within the area investigated, except that a particular somatic antigen found among M. laciniata isolates was limited to one locality. In reciprocal tests between isolates from these two hosts, nodulation has been mainly confined to the homologous host. Although some strains fail in laboratory tests to nodulate the homologous host and although separation into two groups is not complete, there are relatively few cases of discrepancy and many of these show intermediate characteristics. Medicago sativa and Melilotus alba are generally readily nodulated by isolates from both field hosts. The nodulation differences between strains from the two field hosts are paralleled to some extent by serological properties, but it is suggested that this correlation shows recent common origin of similar strains rather than any fundamental relationship between invasibility and antigenic constitution. Effective association was seldom, if at all, achieved with M. laciniata, whereas with other testing hosts effective responses were in the majority and even included a number of isolates originating from M. laciniata and ineffective with that species as host.

Competition between related strains of nodule bacteria and its influence on infection of the legume host

The work deals with the behaviour of mixed strains of nodule bacteria towards each other and towards their legume host. It introduces the concept of dominance in competition between strains. This dominance is independent of degree of effectiveness as regards nitrogen fixation. Where tow strains of nodule bacteria are both present in the surroundings of their host's root system, active competition between them may cause the strain having the higher initial growth rate almost completely to check multiplication of the other strain outside the plant. This dominant strain will then be responsible for nearly all the nodules. In peas and soy beans, where growth of the root sysytem is rapid and of comparatively short duration, the nodule-producing capacity of the plant may be partially or wholly satisfied by the nodules produced within the first few weeks, so that further infection, whether by the same or by a different strain, is checked or inhibited. In clover, whose root system continues to grow over a long period, the first-formed nodules do not stop further nodules from being formed either by the same or by a different strain. There are large differences in the rates of appearance and final numbers of nodules produced by different strains supplied in pure culture, particularly with clover. The relative numbers of nodules produced by the two strains simultaneously applied to the roots is conditioned by the specific infectivity peculiar to each strain, unless some other factor, such as competition outside the plant, masks this effect.

The influence of the host plant in inducing parasitism in lucerne and clover nodules

The relationship of the nodule organism to its host plant has been much discussed, some authors regarding it as an instance of true symbiosis, while others regard the organism as a parasite to which the host plant offers a certain resistance. Failures to obtain inoculation of legumes with strains of nodule bacteria belonging to a different inoculation group may be regarded as examples of such resistance. Even where nodules are formed, the fixation of nitrogen and the benefit derived by the host plant varies according to the strain of the nodule organism concerned (Stevens (1) and Wright (2) ). Some strains, while producing nodules, cause no increase in growth or nitrogen content in the host plant (3) and (4). It is uncertain whether the resistance of the host plant prevents the normal functioning of such strains, or whether they are actively parasitic on the nodule tissue. Strains of the nodule organism thus differ in their relationship to the host plant. The behaviour of a single strain in the tissues may also be altered by the condition of the host plant. Thus, when Vicia faba is grown in a boron-deficient solution, the conducting tissue develops abnormally, so that the vascular supply to the nodules is either absent or incomplete. In such nodules the bacteria fix but little nitrogen and destroy the host cells in which they lie, although the same strain in healthy plants behaves normally and fixes appreciable amounts of nitrogen (Brenchley and Thornton (5) ). It is thus possible experimentally to alter the relationship between the host plant and the bacteria, so that a strain of the latter which is normally beneficial to its host becomes actively parasitic. It was suggested that, in normal nodules, the bacteria derive their energy material from the carbohydrates conveyed to them along the vessels, but that in boron-deficient plants they are to a large extent deprived of their carbohydrates, owing to failure of the vascular supply, and derive energy by attacking the host protoplasm. If this hypothesis be correct, it should be possible to induce the change from symbiosis to parasitism by cutting off the carbohydrate supply in other ways, for example by keeping the plants in darkness.