<I>Azospirillum</I> bacteria form biofilms with <I>Enterobacter cloacae</I> K7 in the root system of wheat seedlings

Biofilm formation has equal adaptive significance for both epiphytic and endophytic rhizobacteria due to their primary localization on the surface of plant roots. The typical strains Azospirillum brasilense Sp7 and A. baldaniorum Sp245 formed biofilms in the root system of wheat (Triticum aestivum L.) mainly in the zones of the root apex and root hairs, as well as in the places of formation of lateral roots. In the case of the strain Enterobacter cloacae K7 isolated from the roots of Jerusalem artichoke (Helianthus tuberosus L.), biofilm formation in certain root zones was not a characteristic feature. Strain K7 colonized the roots, forming biofilms on the surface of the conduction, absorption, and root tip zones. The strains Sp7/Sp245 and K7 were not antagonists, and in the population of their mixed biofilms (studied on the Sp7 and K7 model), the proportions of subpopulations of each strain were approximately the same. However, in the root system of seedlings inoculated with mixed cultures of K7 and Sp7/Sp245, there were areas in the biofilms in which multicellular clusters of one strain were isolated from the cluster of bacteria of the other. Diffuse distribution of Sp7/Sp245 cells among enterobacteria or K7 cells between azospirillum was not typical.