Transport of Rhizobium and Pseudomonas through Soil
1982
Madsen, Eugene L. | Alexander, Martin
A study was made of the vertical movement of Rhizobium japonicum and Pseudomonas putida added to the surface 2.4 cm of nonsterile soil. Recovery of low numbers of these bacteria was possible because the strains were resistant to combinations of inhibitors that prevented growth of most soil microorganisms on agar media. Viable cells of the two bacteria were not transported below 2.7 cm in moist soil in the absence of some transporting agent or in the presence of developing roots of soybeans (Glycine max (L.) Merr.) or beans (Phaseolus vulgaris L.). Percolating water and a burrowing earthworm (Lumbricus rubellus) enhanced the vertical transport of P. putida but had a smaller effect on R. japonicum. Dispersal of both bacteria was more extensive in the presence of percolating water together with L. rubellus or developing roots. Pseudomonas putida was transported farther and in greater numbers than R. japonicum. However, <1 and 4% of the recovered viable cells of R. japonicum and P. putida, respectively, were present below 2.7 cm.
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