Showing papers on "Rhizobia published in 1977"
TL;DR: The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse exp...
Abstract: The effects of soil acidity on nitrogen fixation by alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) were investigated in field experiments at 28 locations, and in greenhouse exp...
124 citations
TL;DR: Maltose, sucrose and polyvinylpyrrolidonc provided a greater degree of protection to both fast- and slow-growing rhizobia than was obtained with montmorillonite, as the polymer only protected the fast-growing Rhizobia and not the slow- growing species.
Abstract: The average number of survivors of fast-growing medic rhizobia (3 strains), fast-growing Rhizobium leguminosarum types (6 strains) and slow-growing species (9 strains) following desiccation of sandy soil inoculated with 106 bacteria·g−1 soil was 727, 795 and 15,682 bacteria·g−1 soil, respectively. Survival in desiccated sandy soil was not influenced by the degree of extracellular polysaccharide production in strains of R. trifolii, nor was it influenced by growth of R. meliloti and slow-growing species in media of low water activity before desiccation in sandy soil. A progressive increase in numbers of fast-growing bacteria surviving desiccation was observed in sandy soil amended with increasing concentrations of powdered montmorillonite, but not with mont-morillonite added as a suspension to the soil. The clay had either a detrimental effect or no effect on the survival of the slow-growing rhizobia. Maltose, sucrose and polyvinylpyrrolidonc provided a greater degree of protection to both fast- and slow-growing rhizobia than was obtained with montmorillonite. The effect of polyethylene glycol 6000 was similar to the effect of montmorillonite, as the polymer only protected the fast-growing rhizobia and not the slow-growing species.
119 citations
TL;DR: It is shown that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate, and it is unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate.
Abstract: The effect of nitrate on the symbiotic properties of nitrate-reductase-deficient mutants of a strain of cowpea rhizobia (32H1), and of a strain of Rhizobium trifolii (TA1), were examined; the host species were Macroptilium atropurpureum (DC.) Urb. and Trifolium subterraneum L. Nitrate retarded initial nodulation by the mutant strains to an extent similar to that found with the parent strains. It is therefore unlikely that nitrite produced from nitrate by the rhizobia, plays a significant role in the inhibition of nodulation by nitrate. Nitrite is an inhibitor of nitrogenase, and its possible production in the nodule tissue by the action of nitrate reductase could be responsible for the observed inhibition of nitrogen fixation when nodulated plants are exposed to nitrate. However, the results of this investigation show that nitrogen fixation by the plants nodulated by parent or mutant strains was depressed by similar amounts in the presence of nitrate. No nitrite was detected in the nodules. Nodule growth, and to a lesser extent, the nitrogenase specific activity of the nodules (μmol C2H4g(-1) nodule fr. wt. h(-1)), were both affected by the added nitrate.
77 citations
TL;DR: It is concluded that gel immune diffusion serology and the use of streptomycin-resistant mutants are both reliable methods for identifying strains of rhizobia reisolated from field environments.
Abstract: Marked strains of Rhizobium trifolii, distinguishable from other strains antigenically and by streptomycin resistance, were introduced by seed inoculation of subterranean clover (Trifolium subterraneum L.) into a field environment having a natural population of R. trifolii. Isolates from nodules obtained periodically during the following 41 months were classified using both methods of identification in parallel. This procedure made it possible to determine the reliability of each method independently. There was a gradual disappearance of the inoculum strains which occurred more rapidly in plots of cv. Woogenellup than in plots seeded with cv. Mount Barker. At five harvests, there was 95% (or greater) correspondence between inoculum survival using either method of identification. There was evidence that a small proportion of the progeny of the inocula sustained independent loss of antigenic character and/or streptomycin resistance in the field or, alternatively, that strains occurring naturally acquired these characteristics. A few nodules contained more than one strain of rhizobia. These exceptions occurred at low frequency and did not interfere substantially with identification results. It is concluded that gel immune diffusion serology and the use of streptomycin-resistant mutants are both reliable methods for identifying strains of rhizobia reisolated from field environments.
77 citations
TL;DR: It is found that a glutamine-dependent auxotroph of Rhizobium cowpea 32H1, deficient in GS activity, is deficient in nitrogenase activity as well, suggesting that GS seems to be involved in the control of nitrogenase expression by Rhzobium.
Abstract: Rhizobia have recently been shown to fix nitrogen while living free1,2,3,4. Unfortunately, free-living fixation occurs only at the end of exponential growth, and there is no condition in which bacterial growth is dependent on reduction of dinitrogen by nitrogenase (EC 1.7.99.2). In the unrelated Klebsiella pneumoniae where fixation does occur in culture, nitrogenase expression is regulated by the enzyme glutamine synthetase (GS) (EC 6.3.1.2). Mutants lacking GS activty (glnˉ) fail to induce measurable nitrogenase activity5,6.
64 citations
TL;DR: Electron micrographs are presented which suggest that rhizobia are freed from the infection thread by disintegration of the thread wall and compartmentalization of the distintegrated wall material in membrane-bound vesicles derived from the membrane surrounding the thread.
Abstract: Root nodules on soybeans (var. Clark 63) were examined by transmission electron microscopy 10–12 days after seed inoculation and planting. The cell infection process appeared identical in both effe...
63 citations
TL;DR: It is shown that the sex-factor R68.45, which promotes chromosomal recombination in Rhizobium leguminosarum2 can also mediate gene transfer amongst strains of R. trifolii and R. phaseoli, which has the possibility of identifying bacterial genes involved in host specificity.
Abstract: THE basis for the symbiotic specificity whereby legumes are nodulated only by rhizobia of the appropriate cross-inoculation group must reside in genetic determinants in both host and bacterium. To analyse the bacterial determinants, crosses between rhizobia of different cross-inoculation groups are necessary. We show here that the sex-factor R68.45 (ref. 1), which promotes chromosomal recombination in Rhizobium leguminosarum2 can also mediate gene transfer amongst strains of R. leguminosarum, R. trifolii and R. phaseoli. These species nodulate peas, clover and French beans respectively; thus there is the possibility of identifying bacterial genes involved in host specificity. The only previous report of interspecific conjugation in Rhizobium described the transfer of a plasmid that determined host specificity in R. trifolii and R. phaseoli3. There have also been reports of transformation of genes, including those determining specificity, between Rhizobium species4,5.
59 citations
TL;DR: It is concluded that colony colour, serological and symbiotic properties are sufficiently stable to be of use in long-term ecological studies although antibiotic sensitivity appears less stable.
Abstract: Rhizobia suited to Lotononis bainesii do not occur naturally in Australia. Two serologically distinct strains of African origin were introduced into an isolated field station where perennial Lotononis-pangola grass pastures are grazed. Paddocks varied in the period of rhizobial occupancy from 5–12 years. Stability of four rhizobial characters: colony colour, effectiveness, cell antigens and antibiotic sensitivity were assessed from nodules on persisting Lotononis. Both strains became established throughout the 782 ha. No changes were observed in colony colour or serological reaction. Symbiotically, 8.5% of isolates had a lower N fixing capacity than stock cultures held in the laboratory although there were no ineffective isolates. Change in effectiveness was unrelated to serotype or to time of occupancy. There was also little change in antibiotic sensitivity although one isolate was tolerant to 15 parts/106 streptomycin. The red bacterium Protaminobacter rubra was recorded for the first time as a cohabitant of Lotononis nodules. It is concluded that colony colour, serological and symbiotic properties are sufficiently stable to be of use in long-term ecological studies although antibiotic sensitivity appears less stable.
49 citations
TL;DR: Results indicate that the incapability of bacteroids to reestablish growth in nutrient media may not be caused by a decrease in nucleic acid content of the symbiotic rhizobia.
Abstract: Populations of symbiotic Rhizobium meliloti extracted from alfalfa nodules were shown by flow microfluorometry to contain a significant number of bacteroids with higher nucleic acid content than the free-living rhizobia. Bacteroids with lower nucleic acid content than the free-living bacteria were not detected in significant quantities in these populations. These results indicate that the incapability of bacteroids to reestablish growth in nutrient media may not be caused by a decrease in nucleic acid content of the symbiotic rhizobia.
39 citations
TL;DR: Inhibition studies of the effect of nitrate and its reduction products on the nitrogenase activity in cultured strains 32Hl and the nitrate reductase-deficient, Nif+ strains, indicated that nitrogen enzyme activity was sensitive to nitrite rather than to nitrate.
Abstract: Forty-eight mutants unable to reduce nitrate were isolated from "cowpea" Rhizobium sp. strain 32Hl and examined for nitrogenase activity in culture. All but two of the mutants had nitrogenase activity comparable with the parental sttain and two nitrogenase-defective strains showed alterations in their symbiotic properties. One strain was unable to nodulate either Macroptilium atropurpureum or Vigna uguiculata and, with the other, nodules appeared promptly, but effective nitrogen fixation was delayed. These results, and the relatively low proportion of nitrate reductase mutants with impaired nitrogenase activity, do not support the proposed commanality between nitrogenase and nitrate reductase in cowpea rhizobia. Inhibition studies of the effect of nitrate and its reduction products on the nitrogenase activity in cultured strains 32Hl and the nitrate reductase-deficient, Nif+ strains, indicated that nitrogenase activity was sensitive to nitrite rather than to nitrate. Images
37 citations
TL;DR: These findings provide the basis for a simple method for simultaneously allowing for N 2 fixation and seed protection of legumes.
Abstract: Isolates of Rhizobium phaseoli resistant to spergon (2,3,5,6-tetrachloro-l,4-benzoquinone), Rhizobium meliloti resistant to thiram (tetramethylthiuram disulfide) and of a cowpea Rhizobium resistant to phygon (2,3-dichloro-l,4-naphthoquinone) were obtained by culturing the bacteria in media with increasing concentrations of these fungicides. The cultures grew in media with 200 μg thiram ml −1 , 150 μg spergon ml −1 or 400 μg phygon ml −1 . Spergon-tolerant R . phaseoli was sensitive to thiram, and thiram-tolerant R . meliloti was sensitive to spergon. The dry weights of beans, alfalfa and cowpeas and the amount of N 2 fixed were the same for plants inoculated with the fungicide-resistant or the sensitive parent rhizobia. However, when the three parent Rhizobium strains were applied to seeds treated with the three fungicides, the plants that developed were stunted, chlorotic, grew poorly and fixed little or no N 2 . By contrast, beans, alfalfa or cowpea plants derived from seeds coated with spergon, thiram or phygon and inoculated with the resistant rhizobia grew as well and fixed as much N 2 as legumes derived from seeds not treated with the pesticides. These findings provide the basis for a simple method for simultaneously allowing for N 2 fixation and seed protection of legumes.
TL;DR: The observed ultrastructural changes suggest either a suddenly manifested incompatibility between host and rhizobia, or an acute, localized, nitrogen starvation in the infected cells.
Abstract: Ineffective nodules, formed on Clark-63 soybeans by Rhizobium japonicum strain 8-0 (Iowa), and effective nodules, formed on Clark-63 soybeans by strain 138 (U.S.D.A.), have been examined by electron microscopy at 10–12, 16, and 21 days after seed inoculation. Though strain 8-0 bacteria are able to infect the host cells in a normal manner, infection is followed closely by a progressive deterioration of the symbiosis involving selective autolysis of host cell contents and degeneration of the intracellular bacteria. The host cells, though disrupted, apparently survive the destruction of the bacteria. The observed ultrastructural changes suggest either a suddenly manifested incompatibility between host and rhizobia, or an acute, localized, nitrogen starvation in the infected cells.
Patent•
30 Aug 1977
TL;DR: Seeds, for example, legume seeds, are coated with a mixture containing a caseinate salt and viable rhizobia bacteria as mentioned in this paper, which is called caseinate-rhizobia mixture.
Abstract: Seeds, for example, legume seeds, are coated with a mixture containing a caseinate salt and viable rhizobia bacteria.
TL;DR: The positive reaction of plant species and families not yet tested shows once more that the capability to undergo nitrogen fixing associations with rhizobia is widespread over the plant kingdom.
TL;DR: A survey of 35 legume species comprising 25 of Papilionoideae, 7 of Mimosoideae and 3 of Caesalpinioideae was made, finding nodulation was found in all the species except for 2 (Caesalpinnia pulcherrima and Cassia siamea), both of which possessed dark coloured roots.
Abstract: A survey of 35 legume species comprising 25 of Papilionoideae, 7 of Mimosoideae and 3 of Caesalpinioideae was made. Nodulation was found in all the species except for 2 (Caesalpinnia pulcherrima and Cassia siamea) of Caesalpinioideae, both of which possessed dark coloured roots. Nodulation is reported for the first time for Adenanthera pavonina and Delonix regia. Nodule shapes were described and classified into different types. The isolates of rhizobia obtained belonged largely to the slow growing group (17 isolates) isolated mainly from members of Papilionoideae; some belonged to the fast growing group (14 isolates), and only 3 isolates belonged to the very slow growing group. The slow growing group isolates were confirmed to be cowpea type rhizobia on the basis of positive nodulation with cowpea plants. re]19750829
TL;DR: The Nile Blue Test detected rapidly, but not slowly growing, strains of agrobacteria present as contaminants of rhizobia cultures even when their initial numbers were small.
Abstract: The ability of agrobacteria to reduce Nile Blue more strongly than do rhizobia is the basis of a test for separating these two groups (Hamdi 1969). In a modified test using only 35 parts 10° of Nile Blue in the medium, 89 of 90 rhizobia (Rhizobium japonicum, R. leguminosarum, R. lupini, R. phaseoli, R. trifolii, cowpea, groundnut and Lotus rhizobia) failed to reduce the dye whereas all 24 strains of agrobacteria (Agrobacterium radiobacter var. radiobacter, A. r. var. tumefaciens and A. r. var. rhizogenes) reduced it to the colourless state. Only one Rhizobium strain formed 3-ketolactose from lactose, but 13 agrobacteria produced it. Rhizobium meliloti strains (12) gave variable reactions in both tests. The Nile Blue Test detected rapidly, but not slowly growing, strains of agrobacteria present as contaminants of rhizobia cultures even when their initial numbers were small.
TL;DR: It is demonstrated that under certain conditions some rhizobia can detoxify canavanine and utilize it in synthetic processes and enhance incorporation of uridine-H3 and L-leucine- H3 into trichloroacetic acid insoluble fractions of starved cells of two strains of rhizophobia tested.
Abstract: Four strains of rhizobia that nodulate canavanine-synthesizing legumes and four strains that nodulate noncanavanine-synthesizing legumes were tested for sensitivity to L-canavanine. The effect of canavanine on growth depends upon the strain of Rhizobium tested rather than the canavanine synthesizing capability of the host legume. In both groups of rhizobia, some strains were inhibited in growth by canavanine. Canavanine enhancement of growth was observed in rhizobia that nodulate noncanavanine-synthesizing legumes.
TL;DR: Root nodule protoplasts, isolated from soybeans under anaerobic conditions, showed nitrogenase activity and rhizobia present in the root nodules (Rhizobium japonicum ATCC No 10324), kept under the same conditions in pure culture showed no nitrogen enzyme activity.
01 Jan 1977-Zentralblatt für Bakteriologie, Parasitenkunde, Infektionskrankheiten und Hygiene. Zweite Naturwissenschaftliche Abteilung: Allgemeine, Landwirtschaftliche und Technische Mikrobiologie
TL;DR: The interrelation between rhizobia and certain fungi, bacteria, actinomycetes, nematodes, and seed-coat diffusates of Phaseolus vulgaris were investigated and the effect of pesticides, i.e. fungicides, herbicides, and nematocides on growth of rhizophobia, and the symbiotic systems between rhZobia and their respective host is reported.
TL;DR: The main pigments of Rhizobium lupini were 2,3,2′,3′-di-trans-tetrahydroxy-β,β-caroten-4-one and 2, 3, 2,, 3′, 6.5
Abstract: The main pigments of Rhizobium lupini were 2,3,2′,3′-di-trans-tetrahydroxy-β,β-caroten-4-one and 2,3,2′,3′-di-trans-tetrahydroxy-β,β-carotene. As minor components 7,8,7′,8′-tetrahydro-ψ, ψ-carotene (ζ-carotene), β, β-carotene (β-carotene), and tentatively, a 2,3,2′(or 3′)-trihydroxy-β, β-caroten-4-one and a 2,3,2′(or 3′)-trihydroxy-β, β-carotene were identified.