effect of biotic and physical factors on the competitive ability of Rhizobium leguminosarum

• Published in: Central European journal of biology 2012-02, Vol.7 (1), p.13-24
• Main Authors: Wielbo, Jerzy, Kidaj, Dominika, Koper, Piotr, Kubik-Komar, Agnieszka, Skorupska, Anna
• Format: Article
• Language: English
• Subjects: Biochemistry; Biomedical and Life Sciences; Biotechnology; carbon; Cell Biology; Competition; edaphic factors; energy; field experimentation; flavonoids; genes; homoserine; host plants; Human Genetics; Immunology; lactones; Life Sciences; microsymbionts; peas; plant tissues; Research Article; Rhizobium leguminosarum; Rhizobium leguminosarum bv. viciae; Rhizobium-legume symbiosis; Rhizosphere; root nodules; Roots; saprophytes; Soil; soil bacteria; Soil microorganisms; soil types; Strain competitiveness; symbiosis; Vicia
• ISSN: 1895-104X; 2391-5412; 1644-3632; 2391-5412
• DOI: 10.2478/s11535-011-0085-x

BACKGROUND: Rhizobium leguminosarum bv. viciae (Rlv) is a soil bacterium which can form nitrogen-fixing symbiotic relationships with leguminous plants. Numerous rhizobial strains found in soils compete with each other. Competition can occur both during the saprophytic growth phase in the rhizosphere and inside plant tissues, during the symbiotic phase. Competition is important as it may affect the composition of rhizobial populations present in the soil and in the root nodules of plants. METHODOLOGY: We examined the link between physiological traits and bacterial competitive ability in eighteen Rhizobium leguminosarum bv. viciae (Rlv) isolates during root nodule colonization using laboratory and field experiments. The competitive ability of R/v strains was measured as the percentage of root nodules colonized by gusA-tagged rhizobia in two types of host plants, peas and vetch. RESULTS: The competitiveness of Rlv strains was significantly affected by soil type and the identity of the host plant. Of the eighteen bacterial traits examined in this study, the metabolic potential (number of utilized carbon and energy sources) and the responsiveness of nod genes to flavonoid activation were most important in affecting the competitive ability of Rlv strains. The amount of acylated homoserine lactones (AHL) produced by the strains was less important in influencing competitiveness. Finally, the preactivation of strains with flavonoids or the addition of AHL to gus-tagged Rlv strains did not significantly enhance competitiveness: of the gus-tagged inoculants in comparison to indigenous soil populations of vetch microsymbionts. CONCLUSIONS: The competitiveness of Rlv strains is dependent upon numerous physiological traits. However, environmental factors such as soil type and the type of host plant may be even more important in affecting rhizobial competitiveness.