Liming and choice of pasture species improve rhizobial persistence in an acidic chromosol (red-brown earth)

2005 ◽  
Vol 45 (3) ◽  
pp. 247 ◽  
Author(s):  
E. A. Roesner ◽  
N. A. Fettell ◽  
J. Brockwell
Keyword(s):  
Nitrogen Fixation ◽  
Soil Ph ◽  
Dry Matter ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Nodule Bacterium ◽  
Nitrogen Response ◽  
Barrel Medic ◽  
Medicago Species

An experiment was conducted to determine the persistence of soil root-nodule bacteria as influenced by different rates of lime and the previous pasture species. The work was done at Condobolin, central-western New South Wales, on a chromosol (red-brown earth), acidic in the upper profile (pHCa 4.6), which was representative of soils for an extensive region of the eastern Australian wheat belt. In autumn 1997, the experimental area was treated with 4 rates (6.0 t/ha, 3.0 t/ha, 1.5 t/ha, nil) of finely-ground agricultural limestone and sown with 5 pasture species: lucerne (Medicago sativa), barrel medic (M. truncatula), subterranean clover (Trifolium subterraneum), rose clover (T. hirtum) and ryegrass (Lolium rigidum). The pastures were removed with herbicide and cultivation in September 2000. The land lay fallow for 9 months and then was sown to wheat (Triticum aestivum) in autumn 2001 and again in autumn 2002. The most probable numbers of soil (0–10 cm) populations of the root–nodule bacterium for Medicago species (Sinorhizobium meliloti) and for the Trifolium species (Rhizobium leguminosarum bv. trifolii) were counted in May 2001 and May 2002. Soil pH, which was significantly (P<0.05) elevated 12 months after liming, declined substantially during the next 4 years although there was no concomitant decline in the pH of unlimed soil. The pasture species were highly productive of both pasture dry matter and nitrogen. The majority of legume pasture nitrogen was a consequence of symbiotic nitrogen fixation. There was a small but significant (P<0.05) dry matter response to application of lime in lucerne and barrel medic, and a larger nitrogen response to liming in lucerne, barrel medic and rose clover. Nitrogen fixation by rose clover appeared suboptimal. It was assumed from the density of plants that large populations of rhizobia developed in the soil during the growth of the legumes. Nine months after removal of the pasture, rhizobia numbers had fallen to low levels but did not fall further during the following year. The initial fall was attributed to high soil temperatures and low soil moisture during the Condobolin summer. The population of rhizobia for Trifolium species was about twice that of the rhizobia for Medicago species but the difference was not statistically significant. Liming had an overriding influence on the size of rhizobial populations, except in plots that had previously grown ryegrass where numbers remained low irrespective of rate of liming. Overall, most probable numbers escalated with each increase in rate of liming, from 10/g soil in the nil lime plots to 708/g in the 6 t/ha lime plots. The rhizobial homology of the pasture species (i.e. Sinorhizobium meliloti for the Medicago species and Rhizobium leguminosarum bv. trifolii for the Trifolium species) had an underlying but major influence on most probable numbers and in determining which rhizobial species occurred more commonly. Estimated populations of rhizobia in soils from homologous legumes were about 8 times those found in soils from non-homologous legumes. The benefits of applying lime to this red-brown earth soil may not have been merely a consequence of correction of low soil pH; increased levels of calcium may also have had a role. The results are discussed in relation to re-establishment of legume leys after the cereal phase of the cropping system.

scholarly journals Succinate Transport Is Not Essential for Symbiotic Nitrogen Fixation by Sinorhizobium meliloti or Rhizobium leguminosarum

2017 ◽  
Vol 84 (1) ◽  
Author(s):  
Michael J. Mitsch ◽  
George C. diCenzo ◽  
Alison Cowie ◽  
Turlough M. Finan
Keyword(s):  
Nitrogen Fixation ◽  
Carbon Source ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Symbiotic Nitrogen Fixation ◽  
Sequencing Analysis ◽  
Wild Type ◽  
Content Type ◽  
Transcriptional Changes ◽  
Symbiotic Properties

ABSTRACTSymbiotic nitrogen fixation (SNF) is an energetically expensive process performed by bacteria during endosymbiotic relationships with plants. The bacteria require the plant to provide a carbon source for the generation of reductant to power SNF. While C4-dicarboxylates (succinate, fumarate, and malate) appear to be the primary, if not sole, carbon source provided to the bacteria, the contribution of each C4-dicarboxylate is not known. We address this issue using genetic and systems-level analyses. Expression of a malate-specific transporter (MaeP) inSinorhizobium melilotiRm1021dctmutants unable to transport C4-dicarboxylates resulted in malate import rates of up to 30% that of the wild type. This was sufficient to support SNF withMedicago sativa, with acetylene reduction rates of up to 50% those of plants inoculated with wild-typeS. meliloti.Rhizobium leguminosarumbv. viciae 3841dctmutants unable to transport C4-dicarboxylates but expressing themaePtransporter had strong symbiotic properties, withPisum sativumplants inoculated with these strains appearing similar to plants inoculated with wild-typeR. leguminosarum. This was despite malate transport rates by the mutant bacteroids being 10% those of the wild type. An RNA-sequencing analysis of the combinedP. sativum-R. leguminosarumnodule transcriptome was performed to identify systems-level adaptations in response to the inability of the bacteria to import succinate or fumarate. Few transcriptional changes, with no obvious pattern, were detected. Overall, these data illustrated that succinate and fumarate are not essential for SNF and that, at least in specific symbioses,l-malate is likely the primary C4-dicarboxylate provided to the bacterium.IMPORTANCESymbiotic nitrogen fixation (SNF) is an economically and ecologically important biological process that allows plants to grow in nitrogen-poor soils without the need to apply nitrogen-based fertilizers. Much research has been dedicated to this topic to understand this process and to eventually manipulate it for agricultural gains. The work presented in this article provides new insights into the metabolic integration of the plant and bacterial partners. It is shown that malate is the only carbon source that needs to be available to the bacterium to support SNF and that, at least in some symbioses, malate, and not other C4-dicarboxylates, is likely the primary carbon provided to the bacterium. This work extends our knowledge of the minimal metabolic capabilities the bacterium requires to successfully perform SNF and may be useful in further studies aiming to optimize this process through synthetic biology approaches. The work describes an engineering approach to investigate a metabolic process that occurs between a eukaryotic host and its prokaryotic endosymbiont.

Identification of soil bacteria expressing a symbiotic plasmid from Rhizobium leguminosarum bv. trofolii

1997 ◽  
Vol 43 (2) ◽  
pp. 164-177 ◽  
Author(s):  
S. Sivakumaran ◽  
B. D. W. Jarvis ◽  
P. J. Lockhart
Keyword(s):  
Dna Hybridization ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Sandy Loam ◽  
Rhizobium Tropici ◽  
Rhizobium Loti ◽  
Rrna Sequencing ◽  
Reference Strains ◽  
Good Agreement

A hundred strains of non-nodulating, Gram-negative, rod-shaped bacteria were isolated from clover–ryegrass pastures on three different soil types and from a sandy loam under lupins. When crossed with Escherichia coli PN200 containing the cointegrate plasmid pPN1, 11 transconjugants gained the ability to form nodules on the roots of white clover (Trifolium repens cv. Grasslands Huia). A nodA probe indicated that they had gained nodulation genes. The identities of these 11 strains and 4 others derived from earlier work on non-nodulating root nodule bacteria, were determined by ribotyping, DNA – DNA hybridization, and partial 16S rRNA sequencing. Good agreement was obtained between the three methods, and 11 of the strains were identified as Rhizobium leguminosarum (6), Rhizobium loti (2), Rhizobium etli (1), Rhizobium tropici (1), and Sinorhizobium meliloti (1). DNA –DNA hybridization indicated that the remaining four strains were related to the Rhizobium leguminosarum reference strains. The existence of several species of non-nodulating rhizobia in pasture soil, including species for which the normal host plant was absent, is discussed in relation to the fate of symbiotic plasmids from Rhizobium seed inoculants. It is also suggested that new species should be named for the geographical region from which they are first isolated rather than the host plant.Key words: Rhizobium, non-nodulating, nonsymbiotic, isolation, identification.

scholarly journals Diversity and numbers of root-nodule bacteria (rhizobia) in Polish soils

2011 ◽  
Vol 74 (1) ◽  
pp. 83-86 ◽  
Author(s):  
Stefan Martyniuk ◽  
Jadwiga Oroń ◽  
Maria Martyniuk
Keyword(s):  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
Root Nodule ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Plant Infection ◽  
Physical And Chemical ◽  
And Chemical Properties

Using a sand pouch-plant infection method, populations of several species of root-nodule bacteria (rhizobia) were enumerated in eighty soils collected throughout Poland. <em>Rhizobium leguminosarum</em> bv. <em>viciae</em> (symbionts of pea, faba bean, vetch) and <em>R. leguminosarum</em> bv. <em>trifolii</em> (symbionts of clover) were detected in 77 and 76 soils, respectively. Most of these soils contained moderate and high numbers of these species of the rhizobia. Symbionts of beans, <em>R. leguminosarum</em> bv.<em> phaseoli</em>, were assessed in 76 soils; of this number 15 soils had no detectable populations of bean rhizobia and in 40 soils high or moderate numbers of these bacteria were found. <em>Bradyrhizobium</em> sp. (<em>Lupinus</em>), root-nodule bacteria of lupine and serradella, were absent in 19 soils, out of 80 tested, and 34 soils were colonised by high or moderate populations of bradyrhizobia. <em>Sinorhizobium meliloti</em>, rhizobia nodulating alfalfa, were sparse in the examined soils; with 56 soil containing no detectable numbers of <em>S. meliloti</em> and only 6 soils harbouring high or moderate populations of this species. The estimated numbers of the rhizobia in the studied soils were also related to some physical and chemical properties of these soils.

Sinorhizobium meliloti in Australian soils: population studies of the root-nodule bacteria for species of Medicago in soils of the Eyre Peninsula, South Australia

2001 ◽  
Vol 41 (6) ◽  
pp. 753 ◽  
Author(s):  
J. Brockwell
Keyword(s):  
Soil Ph ◽  
Soil Type ◽  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
South Australia ◽  
Farming Systems ◽  
Annual Rainfall ◽  
Nodule Bacteria ◽  
Root Nodule Bacteria ◽  
Large Populations

Populations of Sinorhizobium meliloti(formerly Rhizobium meliloti — the root-nodule bacteria for Medicago) from soils at 32 sites on the Eyre Peninsula, South Australia, were enumerated and evaluated for nitrogen-fixing effectiveness in association with Medicago laciniata, M. littoralis, M. polymorpha, M. rugosa, M. tornata and M. truncatula. These symbiotic values were related to physical features of the environment, viz. soil type, soil reaction, mean annual rainfall, and the presence or absence and frequency of occurrence of sown and naturalised annual species of Medicago (medics). Large populations of S. meliloti (ranging from 270 to 460000 per gram of soil) were detected in 28 of the 29 soils where medics occurred. One or more species of medic were found in 29 of the 32 soils examined. The other 3 soils were relatively moist and acidic in reaction with a mean soil pH (CaCl 2 ) of 5.5. It could be inferred that the presence of populations of S. meliloti was dependent on the occurrence of species of Medicago. Other features of the environment had no impact on the size of S. melilotipopulations, except insofar as they influenced the occurrence of medics. All populations of S. meliloti were effective in nitrogen fixation for M. littoralis and M truncatula, the 2 species most commonly sown as legume components of the cereal–pasture farming systems of the Eyre Peninsula. Effectiveness of populations of S. meliloti for M. polymorpha, M. rugosa and M. tornata was significantly greater (P&lt;0.05) in soils where M. polymorpha occurred than where it did not. Otherwise, the symbiotic capacity of the root-nodule bacteria was not influenced by soil type, soil pH, rainfall or the presence or absence of particular medics. There are many indications that medic productivity on the Eyre Peninsula is in decline with detrimental consequences for the nitrogen economy of the farming systems. The almost universal occurrence in soils of the Eyre Peninsula of large populations of S. meliloti that were effective for M. littoralis and M. truncatula indicated that, whatever the reasons for ‘medic decline’, the condition is not attributable to inadequacies of the naturally occurring populations of root-nodule bacteria.

Characterisation of dry and mucoid colonies isolated from Australian rhizobial inoculant strains for Medicago species

2005 ◽  
Vol 45 (3) ◽  
pp. 151 ◽  
Author(s):  
A. McInnes ◽  
P. Holford ◽  
J. E. Thies
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Dry Weight ◽  
Sequence Element ◽  
Shoot Dry Weight ◽  
Single Colony ◽  
Agar Media ◽  
Fixation Capacity ◽  
Medicago Species ◽  
K Antigen

The presence of dry and mucoid colonies in cultures of rhizobial strains used in the production of commercial Australian inoculants is of concern for quality assurance because of the possibility of altered capacity for nodulation and nitrogen fixation by the different colony types. In this study, single colony isolates obtained from dry and mucoid colonies present in commercial cultures of Sinorhizobium meliloti were investigated to identify stability in culture, genetic identity and changes in exopolysaccharide (EPS) production, nodulation and nitrogen fixation. The 2 strains studied were WSM688 and WSM826 (Australian inoculant strains for annual and perennial medics, respectively), both of which produced only mucoid colonies on agar media when originally isolated from nodules. Dry and mucoid single colony isolates from the ‘mother cultures’ of the 2 strains exhibited stable colony phenotypes during successive subculturing in our laboratory and were shown to be most closely related to S. meliloti using 16S rRNA partial sequencing. All isolates produced at least 1 of 3 exopolysaccharides (succinoglycan, EPS II and K antigen) that are required for successful nodulation of Medicago species by S. meliloti strains, as indicated by nodulation of host legumes. Strain WSM826 isolates probably produce succinoglycan, as shown by similarity to the succinoglycan-producing strain Rm1021 in a calcofluor binding assay. In contrast to published work, there was no evidence that loss of mucoidy in dry colony isolates of either strain was associated with the presence of an insertion sequence element in the expR gene that inhibits EPS II production. For strain WSM688, dry and mucoid isolates were identical by PCR fingerprinting and showed a similar capacity to nodulate and fix nitrogen with the target host legume M. truncatula in glasshouse tests. In contrast, strain WSM826 mucoid isolates produced PCR fingerprints that were different from each other and from the WSM826 dry colony isolates. Dry and mucoid colonies may have arisen from substantial genetic change or through contamination of cultures by other S. meliloti strains. One WSM826 mucoid isolate (826-3) produced significantly lower shoot dry weight when inoculated onto both the target host M. sativa and non-target host M. truncatula, even though the capacity to nodulate both hosts was retained. This suggests that this isolate was affected in its nitrogen fixation capacity. Further research is required to identify the origin and extent of colony variation in commercial S. meliloti cultures.

scholarly journals THE INFLUENCE OF SYNTHETIC POLYSACCHARIDE ON BOTH EFFICIENCY OF SYMBIOSIS AND PEROXIDASE AND CATALASE ACTIVENESS OF PEA AND SOYA BEANS

2007 ◽  
Vol 4 ◽  
pp. 62-73
Author(s):  
E.D. Krugova ◽  
N.M. Mandrovska ◽  
S.Ya. Kots
Keyword(s):  
Nitrogen Fixation ◽  
Bradyrhizobium Japonicum ◽  
Rhizobium Leguminosarum ◽  
Plant Biomass ◽  
Metabolic Process ◽  
Activity Level ◽  
Nodule Bacterium ◽  
Antioxidative Defense ◽  
Defense System ◽  
Nitrogen Activity

The influence of synthetic polysaccharide MOD-19 on the effic¬iency of nitrogen fixation ofpea and soya plants as well as on ferment activity of the antioxidative defense system - peroxidase and catalase was investigated. It has been shown that the metabolic process intensifying is ob¬served in pea and soya plants grown from the seeds, wich had been tilled before sowing by nodule bacterium (pea - Rhizobium leguminosarum bv. viciae 263b and soya beans - Bradyrhizobium japonicum 634b) and by nonspecific for these bean cultures polysaccharide MOD-19. This has been proved by morphological and functional haracteristics of these systems, the increasing of plant biomass and nodules quantiity on the roots. The active functioning period of nodules is elongating at the expense of secondary nodules formation on the side roots and their nitrogen activity increased. Rising of the oxidative ferment activity level for peroxydase and catalase was found in these plants.

Symbiosis between the root-nodule bacterium Sinorhizobium meliloti and alfalfa (Medicago sativa) under salinization conditions

Microbiology ◽  
2006 ◽  
Vol 75 (1) ◽  
pp. 77-81 ◽  
Author(s):  
M. V. Ibragimova ◽  
M. L. Rumyantseva ◽  
O. P. Onishchuk ◽  
V. S. Belova ◽  
O. N. Kurchak ◽  
...  
Keyword(s):  
Medicago Sativa ◽  
Sinorhizobium Meliloti ◽  
Root Nodule ◽  
Nodule Bacterium ◽  
Root Nodule Bacterium

scholarly journals Thiamine Is Synthesized by a Salvage Pathway in Rhizobium leguminosarum bv. viciae Strain 3841

2006 ◽  
Vol 188 (18) ◽  
pp. 6661-6668 ◽  
Author(s):  
R. Karunakaran ◽  
K. Ebert ◽  
S. Harvey ◽  
M. E. Leonard ◽  
V. Ramachandran ◽  
...  
Keyword(s):  
Nitrogen Fixation ◽  
Sinorhizobium Meliloti ◽  
Rhizobium Leguminosarum ◽  
De Novo ◽  
Fluorescent Microscopy ◽  
Good Growth ◽  
Wild Type ◽  
Salvage Pathway ◽  
Mesorhizobium Loti ◽  
Reverse Transcription Pcr

ABSTRACT In the absence of added thiamine, Rhizobium leguminosarum bv. viciae strain 3841 does not grow in liquid medium and forms only “pin” colonies on agar plates, which contrasts with the good growth of Sinorhizobium meliloti 1021, Mesorhizobium loti 303099, and Rhizobium etli CFN42. These last three organisms have thiCOGE genes, which are essential for de novo thiamine synthesis. While R. leguminosarum bv. viciae 3841 lacks thiCOGE, it does have thiMED. Mutation of thiM prevented formation of pin colonies on agar plates lacking added thiamine, suggesting thiamine intermediates are normally present. The putative functions of ThiM, ThiE, and ThiD are 4-methyl-5-(β-hydroxyethyl) thiazole (THZ) kinase, thiamine phosphate pyrophosphorylase, and 4-amino-5-hydroxymethyl-2-methyl pyrimidine (HMP) kinase, respectively. This suggests that a salvage pathway operates in R. leguminosarum, and addition of HMP and THZ enabled growth at the same rate as that enabled by thiamine in strain 3841 but elicited no growth in the thiM mutant (RU2459). There is a putative thi box sequence immediately upstream of the thiM, and a gfp-mut3.1 fusion to it revealed the presence of a promoter that is strongly repressed by thiamine. Using fluorescent microscopy and quantitative reverse transcription-PCR, it was shown that thiM is expressed in the rhizosphere of vetch and pea plants, indicating limitation for thiamine. Pea plants infected by RU2459 were not impaired in nodulation or nitrogen fixation. However, colonization of the pea rhizosphere by the thiM mutant was impaired relative to that of the wild type. Overall, the results show that a thiamine salvage pathway operates to enable growth of Rhizobium leguminosarum in the rhizosphere, allowing its survival when thiamine is limiting.

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