The motility of bacteria from rhizosphere and different zones of winter wheat roots

More than 800 rhizobacterial strains were isolated from winter wheat “rhizosphere” (the soil tightly adhering to the roots), “rhizoplane” (the root surface) and “endorhiza” (the interior of the roots) at different plant growth stages (two leaves, four leaves, flowering and full maturity). The data obtained clearly show that the proportion of motile strains gradually increased from “rhizosphere”, through “rhizoplane”, to “endorhiza”. These results strongly suggest that flagellar motility is an important factor in the colonization of plant roots (especially the root interiors) by bacteria. However, high proportions of nonmotile bacteria among the bacterial isolates from the root surface at four leaves and flowering stages suggest that flagellar motility is not an absolutely necessary bacterial feature in colonization of plant roots. Pseudomonads and enterobacteria were the main motile bacteria, and Cytophaga-Flavobacterium the main nonmotile ones. The role of flagellar motility in plant root colonization is discussed in relation to other bacterial traits.