Rhizobium meliloti competitiveness and the alfalfa agglutinin

In the American Midwest, superior N2-fixing inoculant strains of Bradyrhizobiumjaponicum consistently fail to produce the majority of nodules on the roots of field-grown soybean. Poor nodulation by inoculant strains is partly due to their inability to stay abreast of the expanding soybean root system in numbers sufficient for them to be competitive with indigenous bradyrhizobia. However, certain strains are noncompetitive even when numerical dominance is not a factor. In this study, we tested the hypothesis that the nodule occupancy achieved by strains is related to their nodule-forming efficiency. The nodulation characteristics and competitiveness of nine strains of B. japoniwum were compared at both 20 and 30°C. The root tip marking technique was used, with the nodule-forming efficiency of each strain estimated from the average position of the uppermost nodule and the number of nodules formed above the root tip mark. The competitiveness of the nine strains relative to B. japonicum USDA 110 was determined by using immunofluorescence to identify nodule occupants. The strains differed significantly in competitiveness with USDA 110 and in nodulation characteristics, strains that were poor competitors usually proving to be inferior in both the average position of the uppermost root nodule and the number of nodules formed above the root tip mark. Thus, competitiveness was correlated with both the average position of the uppermost nodule (r = 0.5; P = 0.036) and the number of nodules formed above the root tip mark (r = 0.64; P = 0.005), while the position of the uppermost nodule was also correlated to the percentage of plants nodulated above the root tip mark (r = 0.81; P < 0.001) and the percentage of plants nodulated on the taproot (r = 0.67; P = 0.002).

mentioning

confidence: 94%

Competitive Ability and Efficiency in Nodule Formation of Strains of Bradyrhizobium japonicum

McDermoti

Graham

1990

“…Changes in susceptibility for phage due to alterations in cell wall polymers were observed also by Handelsman et al (7). They described a Rhizobium strain which has a low agglutination ability and is resistant to phage F20, whereas its phage-sensitive variant is highly agglutinable.…”

Section: Discussionmentioning

confidence: 63%

“…Several compounds, such as proteins and other polymers, are known to mask the phage receptor in bacteria (16,20,27). Any changes in these polymers may alter the susceptibility for phage and agglutination reaction with lectins (7).…”

Section: Discussionmentioning

confidence: 99%

Properties of the Cell Walls of Lactococcus lactis subsp. cremoris SK110 and SK112 and Their Relation to Bacteriophage Resistance

Sijtsma

Sterkenburg

Wouters

1988

Resistance of Lactococcus lactis subsp. cremoris SK110 to bacteriophage skllG, encoded on the plasmid pSK112, is due to poor phage adsorption. Its phage-sensitive variant SK112, cured of pSK112, adsorbs phages effectively. Incubation of SK112 with concanavalin A remarkably reduced phage adsorption to this strain. This treatment also caused agglutination of SK112 that was not found with SK110, indicating different concanavalin A adsorption characteristics of cell walls of both strains. The differences between the two strains were reduced by a mild alkali treatment of cells. This resulted in a positive agglutination with concanavalin A for both strains and in parallel adsorption of phage skllG to both. Moreover, isolated cell walls of the two strains were investigated, and both bound phage skllG. These observations suggest the presence of phage receptor material in SK112 as well as in SK110. SK110 contained a relatively high level of bound galactose when compared with the phage-sensitive SK112. After the mild alkali treatment, however, the galactose content of SK110 was diminished such that it became comparable with that of SK112. It is hypothesized that the alkali treatment liberates a galactose-containing component from the cell wall and causes phage sensitivity in L. lactis subsp. cremoris SK110.

“…Previous studies have identified factors that contribute to competitiveness. These factors include motility (2,19), cell surface polysaccharides (12,28), and bacteriocin production (27). However, the importance of these factors for competitiveness in the field has not been demonstrated.…”

Section: Discussionmentioning

confidence: 99%

Quantitative comparison of the laboratory and field competitiveness of Rhizobium leguminosarum biovar phaseoli

Beattie

Clayton

Handelsman

1989

Self Cite

Rhizobium leguminosarum bv. phaseoli KIM5s outcompeted strain CE3 in bean (Phaseolus vulgaris L.) root nodulation when plants were grown at any of three field sites, each with a different soil type and indigenous population, or in the laboratory in a sterilized sand, a sterilized peat-vermiculite mixture, or a nonsterile field soil. A mathematical model describing nodulation competitiveness was empirically derived to evaluate the relative competitiveness of the two strains under these conditions. This model relates the proportional representation of the two strains in the inoculum to the proportional representation of nodules occupied by each strain or both strains and provides a measure of competitiveness, which is referred to as the competitiveness index. Statistical comparisons of competitiveness indices showed that the relative competitiveness of KIM5s and CE3 remained constant when the two strains were applied in a constant ratio over a range of inoculum concentrations, from 103 to 107 cells per seed, and when they were applied in various ratios to six P. vulgaris cultivars. Furthermore, the relative competitiveness of KIM5s and CE3 in the laboratory did not differ significantly from their relative competitiveness at the three field sites studied. Thus, a study of the basis for nodulation competitiveness of KIM5s and CE3 in the laboratory has the potential to provide an understanding of competitiveness both in the laboratory and in the field.